Military


Chapter 10

Registrations


Registration is a means of determining cumulative errors and the corrections for those errors. The purpose of this chapter is to explain registrations and their application to the gunnery problem.


Section I

Reasons for Registrations


Registrations should not be needed if the firing unit can meet their portion of the five requirements for accurate predicted fire (minus target location). If the observer cannot provide an accurate target location, the battalion S3 needs to consider providing a survey team to extend survey into the target area and providing common survey to the observers.

If all conditions of weather, position, and material were standard, a cannon firing at a particular elevation and deflection would cause the projectile to travel the range shown in the firing table corresponding to that elevation and charge. Since all standard conditions will never exist at the same time, firing table data must be corrected.

The purpose of a registration is to determine firing data corrections that will correct for the cumulative effects of all nonstandard conditions. With these corrections applied to firing data, a unit can rapidly and successfully engage any accurately located target within the range of their cannons and have a first round FFE capability.

10-1. Accurate Firing Unit Location

Accurate range and deflection from the firing unit to the target also require that the weapons be located accurately and that the FDC knows this location. The battalion survey section uses PADS to provide accurate survey information on the unit location. Survey techniques available to the firing unit can also help in determining the location of each weapon. The FDC can determine the grid location of each piece by using the reported direction and distance from the aiming circle used to lay the battery or platoon.

10-2. Accurate Weapon and Ammunition Information

The actual performance of the weapon is measured by the weapon muzzle velocity for a projectile family-propellant combination. The firing unit can measure the muzzle velocity of a weapon and correct for nonstandard projectile weight and propellant temperature. This is done by using the M90 velocimeter and MVCT M90-2 for each charge, propellant type, and projectile family. Calibration should be conducted continuously by using the M90. Firing tables and technical gunnery procedures allow the unit to consider specific ammunition information (weight, fuze type, and propellant temperature); thus, accurate firing data are possible.

10-3. Accurate Meteorological Information

The effects of weather on the projectile in flight must be considered, and firing data must compensate for those effects. Firing tables and technical gunnery procedures allow the unit to take into account specific met information (air temperature, air density, wind direction, and wind speed) in the determination of accurate firing data.

10-4. Accurate Computational Procedures

The computation of firing data must be accurate. If the five requirements for accurate predicted fire (minus target location) cannot be met, registrations can be conducted to compute data that will compensate for nonstandard conditions. Applying these corrections to other fire missions will allow the unit to determine accurate firing data.

NOTE: If the unit is able to meet the five requirements for accurate predicted fire, it will still be necessary to improve the firing data derived from the GFT. The unit will not be able to fire accurately (first round fire for effect capability) by firing "cold stick" data. Therefore, the use of a met + VE technique will allow the unit to take all measurable nonstandard conditions into account, and derive a GFT setting. Met + VE techniques are discussed in Chapter 11.

10-5. When to Conduct Registrations

a. The FDO must consider the following:

  • Mission.
  • Equipment.
  • Troops.
  • Time.
  • Terrain and weather.
  • Commander's guidance.
  • Tactical situation.
  • Enemy target acquisition assets.
  • Availability and location of observers.
  • Availability, location, and survey accuracy of known points.
  • Type of registration.
  • Assurance of registration validity.

b. A mission conducted only for the purpose of registering does not cause any damage to the enemy. It does, however, expose the firing unit to enemy TA devices. Also, missions conducted solely for the purpose of registering require additional ammunition and time. Therefore, when possible, registration missions should be integrated into other missions, especially when the observer is equipped with a laser.

c. Met + VE GFT settings should be used when accurate MVVS, met data, and survey are available. The amount of corrections needed to adjust onto a target will be minimal. Firing two check rounds from an inferred GFT setting can be an abbreviated registration. Any refinement sent by the observer should be used to adjust the GFT setting.

d. The flow chart shown in Figure 10-1 can be used to help you decide whether or not to conduct a registration.

10-6. Types of Registrations

a. There are two types of registrations: precision registration and high-burst and/or mean-point-of-impact (HB/MPI) registration. Within the two categories are alternate methods of registering that may be more suitable for use in a particular tactical situation.

(1) Precision registration. The precision registration is a technique for determining, by adjustment, firing data that will place the MPI of a group of rounds on a point of known location. The point of known location is called a known point.

(2) High-burst and/or mean point-of-impact registration. The HB/MPI registration determines the mean burst location of a group of rounds fired with a single set of firing data. When the mean burst location (or MPI) has been determined, the chart data (should hit data) are determined and compared to the data that were fired (adjusted-data [did hit data]).

b. Alternate registration types are discussed below.

(1) Radar-observed registration. The radar-observed registration is a form of the HB/MPI registration and is thoroughly discussed later in this chapter.

(2) Abbreviated registration. Any registration that is conducted by using fewer usable rounds than recommended for the precision or HB/MPI techniques is an abbreviated registration. The use of fewer rounds degrades the results of total corrections. However, the use of fewer rounds to determine the mean burst location (MBL) or the use of a larger "acceptance box" (for example, 2 PEs rather than 1 PE from the MPI) is acceptable if the decreased assurance is acceptable to the commander.

(a) Abbreviated HB/MPI registration. An abbreviated HB/MPI registration is conducted exactly like an HB/MPI registration, except fewer rounds are fired.

(b) Met + VE and check round(s). This form of abbreviated registration requires the solution of a subsequent met to an accurately located target and determines adjusted data by adjusting a round(s) fired by use of the met + VE firing data. Final corrections are determined on the basis of observer refinement.

(c) Abbreviated laser registration. The abbreviated laser registration determines total corrections by comparing the data fired to the chart data determined to the burst location.

(d) Adjust-fire missions. Any adjust-fire mission conducted on an accurately located target can be used to improve firing data by determining total corrections on the basis of the observer adjustments. In this case, refinement data must be sent by the observer. The validity of the GFT setting is directly proportional to the accuracy of the target location.

NOTE: Use of the laser with common directional control enables an observer to accurately locate a target to registration-required accuracy.

(3) Offset registration. A platoon or offset position as much as 1,000 to 2,000 meters away from the firing unit center can be used to conduct a registration. The GFT setting determined from the offset position is assumed to be valid for the primary position if common survey and common direction exist between the two positions. A registration from a flank platoon may reduce the vulnerability of the firing unit.

(4) Registration to the rear.

(a) Registering to the rear (or at some azimuth significantly different from the primary azimuth of fire) results in a GFT setting that does not include the primary azimuth of fire within its deflection transfer limits.

(b) To derive a GFT setting for the primary azimuth of lay, apply eight-direction met techniques as follows:

  • Determine position constants by working a concurrent met for the registration azimuth.
  • Using subsequent met techniques, determine the total corrections (in the direction of the azimuth of lay) by reworking the met.

NOTE: The eight-direction met technique is discussed later in this chapter and in detail in Chapter 11.

10-7. Assurance Tables

A registration conducted with fewer rounds than recommended will degrade the accuracy of the determined corrections. Table 10-1 lists the percentage of probability that the mean location of a particular number of rounds is within 1 or 2 probable errors of the actual mean point of impact achieved by firing an infinite number of rounds. As more rounds are fired, the assurance of validity of the MPI is increased. If the tactical situation dictates, the lesser assurance from an abbreviated registration may have to be accepted.

10-8. Registration Corrections and GFT Settings

a. The final step in every registration is the determination and application of registration corrections. Registration corrections consist of total range, total fuze, and total deflection corrections. The total corrections are determined by comparing the chart data (should hit data) to the adjusted data (did hit data) resulting from a registration. When it is impractical to conduct a registration, corrections can be obtained mathematically by use of a met technique. (See Chapter 11.)

b. The total corrections are then used as the basis for a GFT setting. This allows the FDC personnel to apply total corrections to the GFT. With the GFT setting properly applied, it is possible to fire for effect without an adjustment phase on accurately located targets within transfer limits. Total corrections, GFT settings, and transfer limits will be discussed in greater detail later in this chapter. It is important to remember that no registration is complete until registration corrections are determined and a GFT setting is applied.

NOTE: Should hit data (SHD) are data fired under standard conditions that will cause the round to impact at a point of known location. Did hit data (DHD) are data fired under nonstandard conditions that will cause the round to impact at a point of known location.


Section II

Precision Registrations


Precision registration is a technique that requires an observer to adjust a group of rounds fired from the same howitzer so that their mean point of impact occurs at a point of known location (that is, a known point). The point of registration is accurately located (8-digit grid, 10-meter accuracy or 10-digit grid 1-meter accuracy). It can be determined from survey, can be an easily recognized map spotted terrain feature, or it can be any identifiable point located by a laser and should be on common survey with the firing unit, Corrections are determined by comparing the data that actually did hit the target (adjusted data) to the data that should have hit the target (chart data) if standard conditions had existed at the time of firing.

10-9. Objective

The observer's objective in the impact phase of a precision registration is to obtain spottings of two OVERS and two SHORTS along the OT line from rounds fired with the same data or from rounds fired with data 25 meters apart (50 meters apart when PER is greater than or equal to 25 meters). This normally requires the spottings of four separate rounds. Four spottings achieved by firing projectiles with the same data or data 25 meters apart is critical. This critical bracket must be formed by the observer making only range corrections since a deviation correction will introduce a difference in firing data greater than the 25-meter requirement. The observer should not make any deviation corrections after establishing the 200-meter bracket. If he does, then any previous rounds cannot be used as part of the 25-meter bracket. However, a TARGET HIT or RANGE CORRECT will be spotted by the observer as an OVER and a SHORT. The objective of the time portion of the registration is to correct the mean height of burst of four rounds fired with the same data to 20 meters above the target point. The FDC's objective in a precision registration is to determine corrections to firing data on the basis of the observer's corrections and to determine whether or not the objectives were achieved.

10-10. Initiation of a Precision Registration

a. The decision to register is based on the considerations in Section I. After the decision to register has been made, the FDO announces a fire order.

(1) Fire order. When the FDO announces his fire order, he addresses four questions:

(a) What are we going to do? (for example, precision registration)

(b) Where are we going to do it? (for example, known point 1)

(c) With whom? (for example, with T03)

(d) With what fire order considerations? (The FDO does not address fire order SOP items unless he feels that it is necessary to avoid confusion.)

(2) Registering piece. Use only one weapon to fire the registration. It is best to select the piece that is plotted on the firing chart and for which we have accurate MVV information for the registering charge (for example, the BASE PIECE).

(3) Lot. Register the largest calibrated lot of propellant. This lot is used for first-round FFE missions.

(4) Charge selection. Listed below are a few of the factors an FDO should consider when selecting the charge to register.

(a) At what range will most targets be engaged?

(b) If the enemy has a sophisticated sound ranging capability, a lower charge is preferred.

(c) If the enemy has a sophisticated counterbattery radar capability, a higher charge is preferred.

(d) Which charge has the smallest PER for a given range (see the charge selection table in the TFT).

(e) Lower charges produce less tube wear, residue, and noise. They also have better terminal effects with shell HE.

b. When the RATELO hears the fire order, he will announce a message to observer to alert the observer.

(1) MTO. The MTO includes the information from the fire order that pertains to the observer; for example, type of registration, the known point, and fuzes to be registered. If there is no known point, the FDO will direct the observer to select one in a specified area, and the observer will send the location to that point. The FDO will then designate the number of the known point. Because of the possibility of introducing a target location error, this option is least preferred.

(2) Observer's response. After the observer has received the MTO, he will report direction. If the observer is directed to select a known point, he will report the eight-digit grid location and direction. In either case, the report of direction indicates the observer is ready to conduct the registration.

10-11. Conduct of the Impact Phase of a Precision Registration

a. Fire direction procedures for an impact phase of a registration are identical to those used in the conduct of any adjust-fire mission. All observer corrections are plotted on the firing chart and chart data are announced. The computer sends fire commands to the registering piece. Although care should be taken during all computational steps, extraordinary measures should not be used for the conduct of a registration.

b. The final location of the plotting pin on the chart represents the point where the howitzer had to be aimed to have rounds impact on the known point (Figure 10-2). It is not the actual location of the known point. The difference between these locations depicts the effects that all nonstandard conditions had during firing.

c. The data announced after the observer's final impact refinement shows the range and deflection to the point where the howitzers must aim to have rounds impact on the known point. At this point, no projectile is fired and the time phase of the registration begins. The deflection and elevation corresponding to the data measured to the final pin location is called the adjusted data--the data that did hit the known point. Adjusted data will be circled on the record of fire.

10-12. Conduct of the Time Phase of a Precision Registration

a. When the impact phase of the registration is complete, the time phase can be started. The observer's refinement data moved the mean point of impact of the rounds to the known point. At this point, an adjusted deflection and elevation are determined. The adjusted deflection and elevation are did hit data for the known point and the most accurate data with which to begin the time portion.

b. The first fuze setting fired corresponds to the adjusted elevation. The initial fuze setting to fire is determined by placing the MHL over the adjusted elevation and reading a fuze setting corresponding to that adjusted elevation. At the same time, the computer determines FS corresponding to the first fuze setting fired.

c. As with other fuze time missions, an HOB correction (20/R) is added to the ground site to determine a total site. The total site is added to the adjusted elevation to determine the quadrant to fire for the rest of the mission. The adjusted deflection is fired for the rest of the mission.

d. Normal procedures for application of FS for up or down corrections are followed to meet the objective of the time phase of the mission, which is to correct the mean height of burst of four rounds fired with the same data to 20 meters above the known point.

e. The adjusted time is determined after the observer's HOB refinement is applied. The adjusted time is circled. With the observer's correction applied, the adjusted time will produce an airburst 20 meters above the known point. The adjusted time is not fired.

10-13. Second Lot Registrations

a. The use of the second lot registration technique has become obsolete with the use of the M90 chronograph and the ability to account for muzzle velocity differences in propellant lots. The GFT settings for subsequent lots can be determined by using the subsequent met techniques if muzzle velocity information is available.

b. Conduct second lot registrations in the same manner as single lot registrations with the following exceptions:

(1) Fire order. The fire order informs the FDC that corrections are needed for two different lots (of the same charge and propellant type).

(2) MTO. The radio operator transmits the MTO notifying the FO to observe two lots by announcing TWO LOTS after the fuze or fuzes to be fired.

10-14. Initiation of the Second Lot Registration

a. After completing the first lot time registration, begin firing the first round of the second lot registration with the adjusted deflection and the adjusted quadrant elevation (adjusted elevation plus ground site) determined for the first lot. Fire fuze quick only. To notify the observer that a second lot registration is going to be conducted, the FDC announces: OBSERVE SECOND LOT, OVER.

b. In the appropriate columns on the ROF, enter the firing data determined from the first lot registration. These data include the following:

  • Adjusted deflection.
  • Adjusted chart range.
  • Value of ground site.
  • Adjusted elevation.

c. The adjusting piece must be given commands to change the method of fire, lot and fuze. The objective of the second lot registration is the same as that of the first lot. Once the observer has met the objective, he will announce (any refinement) and RECORD AS SECOND LOT REGISTRATION POINT, END OF MISSION.

d. To determine the adjusted fuze setting, add the fuze correction from the first lot to the fuze setting corresponding to the subsequent lot adjusted elevation. To determine the adjusted fuze setting for the second lot registration, follow the steps in Table 10-2.

e. The second lot GFT setting will be constructed in the same manner as the first lot GFT setting.

NOTE: To minimize confusion, the second lot GFT setting should be placed on a different cursor and labeled with the appropriate lot.

f. Determine the total deflection correction by using the following formula:

2D LOT ADJ DF - CHART DF = TOT DF CORR

g. Determine the GFT deflection correction by placing the MHL over the second lot adjusted elevation and reading the value under the MHL on the drift scale. This value is subtracted from the total deflection correction, and the LARS rule is used to determine whether the GFT deflection correction is a L or an R.

TOT DF CORR - DRIFT ~ 2D LOT ADJ EL = GFT DF CORR

10-15. Example of a Completed Precision Registration

a. Use Table 10-3 to process a precision registration with fuzes quick and time.

b. The observer ends the impact phase of the registration by providing refinement data and requesting RECORD AS REGISTRATION POINT (announces the number of the registration point), TIME REPEAT. Record this transmission on two lines of the ROF. The first line is used to determine the adjusted elevation and adjusted deflection. The adjusted data are determined by processing the refinement data. These adjusted data are referred to as DHD and are recorded and circled on the record of fire for quick reference. The adjusted data are not sent to the howitzer(s).

c. Once the refinement data have been processed, the time phase is initiated. The chart data, deflection to fire (adjusted deflection), and elevation (adjusted elevation) have already been determined. The only data that needs to be computed are the time fuze setting (should hit) and the quadrant elevation. Use the steps in Table 10-4 to process the time phase of the registration.

d. After spotting the last round, the observer will provide final refinement data to adjust the mean height of burst to 20 meters. The observer will also direct RECORD AS TIME REGISTRATION POINT, END OF MISSION. Record this transmission on two lines of the ROF. The first line is used to process the final HOB correction and determine the adjusted time (did hit). The adjusted time is recorded and circled on the record of fire for quick reference. These data are not sent to the howitzer(s). The second line is used to record end of mission, which is sent to the howitzer(s). Once EOM is sent to the howitzer(s), a final police of the ROF is conducted. A completed ROF for a precision registration using the M582 time fuze is shown in Figure 10-3.

10-16. Abbreviated Precision Registration

a. The tactical situation or ammo restraints may prohibit conducting a full-scale registration. In such cases, the FDO may conduct an abbreviated precision registration. Although having a lower assurance of validity, an abbreviated precision registration often provides adequate compensation for the effects of nonstandard conditions. The observer ends the registration when he believes that his next correction will put the next round on the registration point. The advantages of this type of registration are fewer rounds are fired so less ammunition is consumed and the registration takes less time so the unit is exposed to enemy TA devices for a shorter period of time.

b. After making the decision to register, the FDO announces a fire order. Once the RATELO hears the fire order, he transmits an MTO to alert the forward observer. After the observer has received the MTO, he sends a direction, which signifies he is ready to observe, to the FDC.

c. The observer procedures for an abbreviated precision registration those used for a normal precision registration.

(1) The observer will use normal adjust-fir procedures until 100-meter bracket is split.

(2) The correction then sent is an add (or drop) 50 meters FFE or time repeat or time add or drop 50 meters.

(3) The burst which is a result of an add (or drop) 50 meters is spotted. Minor corrections for both deviation and range are sent to the FDC in the following format:

(a) For both a quick and time registration: L10, -40, RECORD AS REGISTRATION POINT, TIME REPEAT.

(b) For an impact only registration: R30, -10, RECORD AS REGISTRATION POINT, END OF MISSION.

(c) Normal time adjustment procedures are followed in the time portion.

(d) Once an airburst is obtained, a correction for a 20-meter HOB is determined.

(e) Instead of firing for effect, refinement is sent to the FDC in the following format: U5, RECORD AS TIME REGISTRATION POINT, END OF MISSION.

NOTE: If the abbreviated registration is conducted as part of a normal adjust-fire mission, steps c(2) and c(3)(e) are modified to allow the observer to request FFE.

d. The GFT setting and total corrections are determined in the same manner as in a normal precision registration. A completed ROF for an abbreviated registration using the M582 time fuze is shown in Figure 10-4.


Section III

High-Burst/Mean Point of Impact Registrations


When registration is necessary, clearly defined and accurately located registration points may be limited or not available. Dense vegetation or ground fog may prevent the observers from seeing the ground. At night, adjustment of fire on a registration point is impossible without some type of illumination. The tactical situation may not allow the firing of numerous rounds required for a precision registration. The HB/MPI registration can overcome these problems. This section describes HB and MPI registrations.

10-17. Description

a. In HB and MPI registrations, the unit fires a number of rounds (ideally six) with the same set of firing data. These rounds are observed by two observers in surveyed positions, usually designated O1 and O2, who can measure the direction to each bursting round. One observer measures the VA to each round. On the basis of the observers' average directions and the average VA from one observer, determine and plot the MBL or the mean point of impact. Lastly, determine chart data and compare them to the adjusted data that were fired.

b. An MPI registration is fired with fuze quick. The HB registration is freed with time-tied rounds. The HB offers an advantage over the MPI registration by allowing the FDC to determine a fuze correction. The HB registration is also easier to observe, especially at night, and registration corrections can be determined in areas where the observers cannot see the ground.

c. The requirement for surveyed observer locations with directional control is the primary limitation of HB and MPI registrations.

d. The six basic steps to an HB or MPI registration are as follows:

  • Select an orienting point.
  • Orient the observers.
  • Determine firing data to the orienting point.
  • Fire the HB or MPI registrations.
  • Determine the mean burst location.
  • Determine chart data and registration corrections.

10-18. Selecting an Orienting Point

a. The S3 or FDO selects an orienting point at which all of the rounds will be fired. This point may be located at a grid intersection for convenience. The orienting point is only a temporary point on the firing chart. After computing firing data, the orienting point is no longer needed.

b. The orienting point for either an HB or MPI registration point should meet the following criteria.

(1) It must be visible to both observers.

(2) It should be close to the center of the area of responsibility (unless an eight-directional met technique is to be used to determine a valid GFT setting).

(3) It should ensure an acceptable apex angle (Figure 10-5). (The apex angle is the angle formed by the lines from each observer to the orienting point.) Since two of the methods used to determine the MBL involve the use of trigonometry (polar plot and grid coordinate), a strong apex angle is needed to minimize the effects of small measurement errors. More information can be found in FM 6-2.

(4) For an MPI registration, the orienting point should be in a relatively flat (level) area to eliminate the need to replot the MBL.

(5) For an HB registration, the orienting point must be high enough to ensure an airburst. The selected height of burst must be at least 2 FE in height of burst above the ground expressed up to the next 10 meters. The FDO can increase the HOB as long as it exceeds the minimum selected HOB. An example of this is below.

c. The FDO initiates the HB/MPI registration with a fire order; for example, HIGH-BURST REGISTRATION AT GRID 4128, HEIGHT OF BURST PLUS 30, WITH T03 AND C19, 6 ROUNDS, FUZE TIME, BY ROUND AT MY COMMAND. As with any registration fire order, this one specifies what will be done, where it is to be done, with whom, and with what fire order considerations (see paragraph 10-10). The FDO has specified BRAMC to be sure that the observers have enough time to spot each round fired and transmit spottings before the next round is fired.

10-19. Orienting the Observers

a. After selecting the orienting point and issuing the fire order, the two observers must be told where to look to observe the rounds. Plot the observers' locations on the firing chart (if not already done), and measure the direction and distance from each observer to the orienting point. The VCO uses the distances and the VI between each observer location and the orienting point to determine the VA for each observer. Determine the VA by use of the C and D scales of the GST.

b. Send a message to each observer. The MTO contains the information the observers need to orient their instruments. Record the MTO on DA Form 4201. (See Figure 10-6.) The message contains the following elements:

(1) A warning order (for example, OBSERVE HIGH-BURST REGISTRATION). The warning order informs the observers for what type of registration they are preparing.

(2) Orienting data for O1 (T03). The HCO measures the chart data from O1 to the orienting point. The direction reported to the observer is the direction determined on the firing chart. The VCO determines the ground altitude of the orienting point and then adds the HOB to determine the altitude of the orienting point. The VCO subtracts the altitude of the observer from the altitude of the orienting point to determine the vertical interval. The VCO uses the C and D scales of the GST, the vertical interval, and the distance measured by the HCO to determine O1's vertical angle. The vertical angle and direction reported to O1 will enable him to orient on the orienting point.

(3) A directive to O1 to measure the vertical angle. Normally, O1 is the more experienced observer and will measure the VA. Observer O1 measures the vertical angles that will be used to compute the altitude of the mean burst location. Only one observer reports the vertical angle.

(4) Orienting data for O2 (C19). The HCO measures the chart data from O2 to the orienting point. The VCO subtracts the altitude of the observer from the altitude of the orienting point to determine the vertical interval. The VCO uses the C and D scales of the GST, the vertical interval, and the distance measured by the HCO to determine O2's vertical angle. The vertical angle and direction reported to O2 will enable him to orient on the orienting point.

(5) A directive to the observers to report when they are ready to observe. When the observers report that they are ready to observe, the FDC can begin the registration.

c. Each observer orients his instrument on the direction and vertical angle announced to him and announces when he is ready to observe the registration.

10-20. Determining Firing Data

a. The HCO determines the range and deflection from the firing unit to the orienting point and announces the data to the computer.

b. The VCO subtracts the altitude of the firing unit from the orienting point altitude to determine the vertical interval. He then uses the D scale and the site-range scale of the GST, the vertical interval, and the range announced by the HCO to determine site. The VCO announces site to the computer.

c. The computer records the site on the ROF and determines and announces the fire commands to the howitzer(s). The HOB correction (20/R) is not used for the HB registration since the HOB was already accounted for in the orienting point altitude. The data fired are the adjusted (did hit) data.

10-21. Firing the HB or MPI Registration

a. After both observers and the registering piece have reported ready, the FDO directs FIRE THE REGISTRATION. The first round that is fired may not be observed by either of the observers. There may be cases in which the nonstandard conditions cause the round to impact behind a hill or in a ravine, out of sight of one or both of the observers. Sometimes graze bursts occur at the start of an HB registration. The observers' data for these rounds cannot be used to determine the mean burst location. If this happens, change the firing data to the orienting point by increasing the HOB by at least 2 additional probable errors in HOB (Table G of the TFT) until both observers can see the bursting rounds (see paragraph 10-18). Remember, if the orienting point is changed, new orienting data must be sent to the observers (that is, a new MTO) so that they can orient on the new location.

b. Once both observers have spotted the round, the firing data are not changed. All rounds used to determine the MBL and/or MPI must be fired with the same set of firing data. These firing data are adjusted (did hit) data.

c. When both observers have reported that they have observed the bursting round, the computer transfers the firing data from the ROF to DA Form 4201 and writes "SEE ATTACHED DA FORM 4201" on the ROF. Record all information for the rest of the registration on DA Form 4201.

d. After observing each round, each observer reports the direction to the round and O1 reports the vertical angle. The computer records the data on DA Form 421 as it is sent by the observers. The FDO must determine if any rounds fired were erratic and their spotting discarded. There are no exact rules for determining which rounds are erratic. The following are methods in which erratic rounds may be determined.

(1) Determine the MBL by using graphic intersection (see paragraph 10-22). Using the range to the MBL (expressed to the nearest 100 meters and interpolated), determine the PER and PED and construct a rectangle (8 PER x 8 PED) centered over the MBL and along the GT line. Reject any rounds that plot outside this rectangle. (See Figure 10-7.)

NOTE: All rounds should have functioned within the 100 percent rectangle defined by ±4 PER and ±4 PED. Any rounds outside of the rectangle are considered erratic.

(2) At the range to the MBL, expressed to the nearest 500 meters, determine the PEHB. Using O1's reported vertical angles, the measured distance from O1 to the MBL, and the ground altitude, determine the MBL altitude. Determine the altitude of each round, and compare this altitude with the average altitude. Reject any round that falls outside the average altitude ±4 PEHB.

(3) The FDO may use his judgement and experience in determining if a round should be rejected. Care must be taken to ensure that erratic rounds are not used or that usable rounds are not rejected. If a round is considered erratic because of the reported direction from O1 or O2 or because of an incorrect vertical angle, the data from the other observer must also be discarded.

10-22. Determine the Mean Burst Location

a. List the observers' measured azimuths (spottings) on DA Form 4201 (Figure 10-8) as they are sent by the observers. As the rounds are fired, circle the round number to record the expenditure of rounds during the registration. Some rounds may be considered erratic. Erratic rounds are crossed out, and additional rounds may be fired to replace them.

b. Once the data from the usable rounds are recorded, the FDC determines the MBL. Determine the location by one of three methods. The methods are listed below in increasing order of accuracy and time of computation. The method used by the FDC will depend on the tactical situation. Usually, the graphic intersection method is acceptable. However, when increased accuracy is needed, use one of the other methods if time permits. See paragraph 10-24 for specific steps.

(1) Graphic intersection. Draw the observers' average directions on the firing chart. The point at which the lines intersect is the mean burst location.

(2) Polar plot. Determine the direction and distance from O1 to the mean burst location, and polar plot the MBL on the firing chart.

(3) Grid coordinates. Compute the actual grid coordinates of the MBL, and plot the coordinates on the firing chart.

10-23. Example of an HB/MPI Registration

a. The steps in Table 10-5 are used to process an HB/MPI registration.

NOTE: A completed ROF for an HB registration using fuze M582 is shown in Figure 10-9.

10-24. Determination of the MBL

a. After all rounds have been fired and the observer spottings recorded, the FDO will determine if any rounds fired were erratic and should be discarded. If any round(s) are discarded, the FDO may decide to fire more rounds. If more rounds are to be fired, the method of fire and QE will be recorded on the ROF and announced to the registering piece. Use the procedures in Table 10-6 to determine the average observer readings.

b. The MBL is determined by using one of the methods below.

(1) Graphic intersection. The HCO orients the RDP by using the average direction of O1. Once the RDP is oriented, a line is drawn along the arm of the RDP by using a 6-H pencil. He repeats the same procedure from O2 by using O2's average direction. The point at which the two lines intersect is the mean burst location. The HCO places a plotting pin at the MBL and determines and announces the distance from O1 to the MBL. The VCO uses the average vertical angle of O1, the O1 distance to the MBL, and the GST to determine and announce the vertical interval between O1 and the MBL. The computer adds the vertical interval to O1's altitude to determine the altitude of the MBL (O1 ALT + VI = MBL ALT). Figure 10-10 can be used to aid in the determination of the MBL altitude. If this aid is used, it is recorded in the margin of DA Form 4201. A completed DA Form 4201 is shown in Figure 10-11 for the graphic intersection technique.

(2) Polar plot. Use the procedures in Table 10-6 and DA Form 4201 (Figure 10-12) to determine the MBL.

(3) Grid coordinate. The steps in Table 10-7 and a DA Form 4201 (see Figure 10-14) are used to determine the MBL.

NOTE: A completed DA Form 4201 for the grid coordinates technique is shown in Figure 10-14.

10-25. Determine Chart Data and Registration Corrections

After plotting the MBL on the firing chart, the HCO determines and announces the chart range and deflection from the firing unit to the MBL. Use Table 10-8 to determine the GFT setting.

10-26. Effect of Complementary Angle of Site on Adjusted Fuze Setting

a. Fuze setting is determined as a function of elevation and complementary angle of site. When the vertical interval is equal to or less than 100 meters, the CAS is generally so small that it has little effect on the quadrant and fuze setting fired and is disregarded. If the vertical interval is greater than 100 meters, the value of the CAS becomes increasingly large and begins to affect the fuze setting. In this case, the CAS must be added to the elevation to determine the proper fuze setting.

b. As the CAS increases, the fuze setting also must be increased to reach the desired burst location. If the effect of CAS is not included in the fuze setting, the fuze will function before it reaches the desired location.

c. If the vertical interval is greater than 100 meters, modify the adjusted the setting to correct for the inaccuracy introduced by the large complementary angle of site. The 100-meter VI is only a rule of thumb; CAS may affect the adjusted fuze setting at vertical intervals of less than 100 meters. The FDO should check the effects of CAS anytime he feels it will affect the adjusted fuze setting. Use Table 10-9 to correct the effect of complementary angle of site on adjusted fuze setting when VI is greater than 100 meters.


Section IV

Process an AN/TPQ-36 or AN/TPQ-37 Radar Registration


Field artillery radars can be used to observe registrations. The conduct of a radar-observed registration (commonly known as a radar registration) is similar to that of other HB or MPI registrations. This section outlines the unique procedures and requirements for the AN/ TPQ-36 (Q-36) and AN/TPQ-37 (Q-37) radar systems.

10-27. Characteristics

a. The Firefinder radar has two separate modes of operation. The first mode of operation is the friendly fire mode, which is used by friendly artillery and mortar units for adjust-fire missions and registrations. The second is the hostile mode, which tracks incoming projectiles and is used to locate enemy indirect-fire systems.

b. A peculiarity of the two separate modes of operation is how the radar operator inputs data into his computer to orient the radar. Data can only be input while the radar is in the hostile fire mode. Once the operator has input all the data into the computer, he switches from hostile to friendly mode, and a delay is experienced while the radar orients itself. If a problem is encountered during the registration, such as around being unobserved, the first thing the operator does is verify his data. This requires him to switch back to the hostile mode, verify his data, then return to the friendly fire mode. Each time he changes modes, the radar physically reorients itself, taking from 20 to 30 seconds.

c. The radar has three different mission buffers, and they are used to store all the data needed to conduct a friendly fire mission. The radar also has the capability to store the spottings for six rounds. When the friendly fire storage cues are full and another round is tracked, it will replace the oldest spotting with the new one. Unless an observed round is recorded by the radar operator or transmitted to the FDC, these old data are lost when they are automatically replaced by the radar computer. Therefore, the operator needs to monitor the mission and either transmit each individual spotting to the FDC or clear the buffer by deleting erroneously captured information.

d. A danger area exists to the front of the radar. Theoretically, VT fuzes can function prematurely within the danger area or as a result of passing through the danger area. For the Q-36, the danger area is 107 meters out from the radar; for the Q-37, it is 141 meters.

(1) The radar takes 9 seconds to warm up before operation.

(2) Minimum observing distance for the Q-36 is 750 meters; for the Q-37, 3,000 meters.

(3) The friendly fire mode has five different mission types that the radar can conduct. They are as follows:

    • Mortar datum plane (MD).
    • Mortar impact prediction (MI).
    • Artillery airburst (AA).
    • Artillery datum plane (AD).
    • Artillery impact prediction (AI).

e. The two types most commonly used by artillery are the artillery airburst (HB registration) and the artillery impact prediction (adjust-fire missions and MPI registrations). One of the problems occasionally encountered between the FDC and the radar section is the use of different technical language. For example, in the message to observer, you might announce OBSERVE HIGH BURST REGISTRATION to orient the radar. An inexperienced radar operator unfamiliar with artillery terminology may have selected an incorrect mission type, which will result in rounds unobserved or unsuitable data. By understanding the different mission type requirements for radar, mistakes are prevented.

f. The advantages of a radar registration include the following:

  • Requires only one observation post--the radar.
  • Requires less survey, fewer communications facilities, and less coordination than other HB or MPI registrations.
  • Can be conducted quickly.
  • Can be conducted in periods of poor visibility.
  • Produces the MBL/MPI grid and altitude or the grid and altitude of each round.

g. The disadvantages of a radar registration include the following:

  • Exposes radar to detection from the enemy.
  • Keeps radar sections from performing their primary mission.
  • May need to reposition radar to conduct the registration.

10-28. Conduct of a Radar Registration

The six steps in conducting a radar registration are as follows:

  • Select an orienting point.
  • Orient the radar.
  • Determine firing data to the orienting point.
  • Fire the HB or MPI registration.
  • Determine the mean burst location.
  • Determine chart data and registration corrections.

10-29. Selection of an Orienting Point

a. The radar must be properly sighted in relation to friendly units to fully use its capabilities. There are three areas that significantly impact the ability of the radar to track friendly fire. They are as follows:

  • Electrical line of sight.
  • Range from the radar to the target.
  • Aspect angle (T).

(1) A radar must have electrical line of sight to the point along the descending branch of the trajectory of the round where the burst will occur (HB), or it must be able to track the projectile for enough time to predict its point of impact (MPI). Doctrine calls for radar to be sited in defilade to increase its survivability. This means that there are intervening crests (screening crests) between the radar and the area where the rounds are being fired.

(2) If these crests interfere with the radar's electrical line of sight, then the radar search fence must be oriented high enough so that these crests will not mask the emissions. However, if the radar is oriented above the altitude that the time fuzes are set to function, then ROUND UNOBSERVED will very likely be received from the radar. The easiest way to counteract this problem is to modify the procedures normally used to select a height of burst for HB registrations so that the radar is sure to "see" the burst.

(3) Aspect angle is the angle that is formed by the intersection of the gun-target line and the radar-target line, with the vertex of the angle at the target (T) (be less than 1,200 mils, with 800 mils being the optimum. A less than optimum aspect angle is going to decrease the probability of tracking each round. (From 1,300 to 1,600 mils, the tracking picture becomes fuzzy with the probability of track decreasing significantly.) These factors must be considered when determining whereto site your radars to optimize their performance.

b. A high-burst registration conducted with the Q-36 or Q-37 radar requires only an electrical line of sight to the selected point. The on-board computer controls the radar to enable it to intersect the trajectory above the screening crest. The radar tracks the round until the airburst is detected. The Q-36 and Q-37 radar systems set up a "window" through which the projectile will pass. The window is referred to as the friendly fire search fence (Figure 10-15). The search fence allows for the best probability of detection. Because of the size of the radar memory queue, no more than six rounds should be fired without coordination with the radar section. Rounds should be fired at 30-second intervals with an angle T of less than 1,000 mils.

c. MPI Registration. A characteristic of the radar MPI registration is that the rounds usually cannot be observed at impact because the radar usually is positioned behind masking terrain with a screening crest. The projectile is tracked until it reaches the datum plane height. The radar section reports the grid and altitude of the impact location as predicted by the radar.

10-30. Orienting the Radar

a. After selecting the orienting point, the FDO issues his fire order and the FDC computes orienting data. The registration is initiated by transmitting an MTO. The purpose of this message is to inform the radar section of the mission and to provide the information required to prepare the radar.

b. The message to observer must always include the warning order. It is OBSERVE HIGH-BURST (or MPI) REGISTRATION FOR (unit call sign). This informs the radar section of the type of registration to be fired and for whom the registration is conducted. Observe communications security procedures in transmitting information.

c. To orient the AN/TPQ-36 or -37 radar, send the radar the following:

  • Grid and altitude of the orienting point.
  • Grid and altitude of the firing unit.
  • Quadrant elevation.
  • Maximum ordinate (to the nearest meter) from the appropriate TFT. Entry argument is quadrant elevation (interpolate). Special if it is meters or feet and above sea level or above gun.
  • Time of flight.
  • Target number.
  • Angle of fall. (Determined by interpolation from Table G by using quadrant elevation as the entry argument.) This is optional.

d. Regardless of the radar system used, the message to observer must include the report order. It is REPORT WHEN READY TO OBSERVE.

10-31. Determination of Firing Data to the Orienting Point

The determination of firing data for a radar registration is the same as that for a regular HB or MPI registration.

10-32. Firing the HB or MPI Registration

The radar on-board computer uses the orienting data to check the trajectory and determine whether it fits the capabilities of the radar. Before firing, the radar operator determines whether the data are acceptable, marginal, or unacceptable. The radar section reports when it is ready to observe (for example, AT MY COMMAND, REQUEST SPLASH, READY TO OBSERVE, OVER). Since the radar operator checks the acceptability of the orienting data before firing begins, all rounds fired should be acquired by radar. If the first round is not visible, an error has occurred. The radar operator informs the FDC that the round was unobserved. The FDC should verify firing data, If no errors are found and the next round is unobserved, the FDC should compute new orienting data and send the new data to the radar operator.

10-33. Determination of the Mean Burst Location

The radar operator normally reports the grid location and altitude of each burst. The grids may be recorded in the observer reading columns of DA Form 4201. The FDO determines which rounds are usable. Once the FDO determines the usable rounds, he averages the grids and altitudes of the usable rounds to compute the mean burst location. The grid and altitude are then recorded in the Location of HB (MPI) block near the bottom of DA Form 4201.

10-34. Determination of Chart Data and Registration Corrections

After determining the MBL and altitude, the procedures for computing chart data and registration corrections are the same as those for regular HB/ MPI registrations. Figure 10-16 shows an example of a completed ROF for an HB radar registration. Figure 10-17 shows an example of a completed DA Form 4201 for an HB radar registration.

10-35. DPICM Registrations (M483A1/M509E1)

a. The DPICM projectile may be fired in the self-registration mode to provide corrections for other munitions like the area denial artillery munitions (ADAM) or remote antiarmor mine system (RAAMS). The round can be registered by using either the precision or the HB/MPI method. Normally, the HB/MPI method would be selected to conserve ammunition.

b. Firing data should be computed by using the most current firing table.

c. If point-detonating action is desired for an impact registration, the M577 fuze must be set for PD action. An impact registration is not recommended, since no fuze setting correction is determined.

d. In all cases when the round is used in registrations, it must be prepared for the SR mode (expelling charge removed and booster attached to fuze). In the SR mode, the entire round will detonate and destroy the submunitions.

e. The GFT setting is constructed and total corrections are determined as per precision and HB/ MPI instructions. An example ROF for a completed precision registration for shell DPICM is shown in Figure 10-18. The HOW 155mm 155AN1M483A1 GFT was used for the registration.


Section V

High-Angle Registration


On the basis of the tactical considerations, it may become necessary to use high-angle fire instead of low-angle fire. In this situation, a high-angle impact registration can be conducted to improve the accuracy of initial rounds. The use of time fuzes to conduct a time registration is impractical because the height of burst probable error is so large.

10-36. High-Angle GFT

When conducting a high-angle impact registration, it is common for the range probable error to be equal to or greater than 25 meters. Since current high-angle GFTs do not have a probable error in range gauge point, the computer must check Table G of the TFT to determine if the probable error in range is equal to or greater than 25 meters. A probable error in range gauge point may be constructed on the high-angle GFT for each charge. The gauge point is constructed on the TF scale.

10-37. Procedures for High-Angle Impact Registration

Procedures for high-angle impact registrations are the same as low-angle impact registrations with the following three exceptions:

a. Because of the large CAS in high-angle fire, special procedures must be used to determine the adjusted elevation.

b. The high-angle GFT setting is applied differently to the high-angle GFT.

c. High-angle transfer limits are different from low-angle transfer limits because ranges of various charges are smaller.

10-38. Computation of the Adjusted Elevation

a. The adjusted elevation, determined from an HA impact registration, often includes a false site. This false site is caused by the relationship of the CAS to total site. The CAS is a fiction of elevation. In low-angle fire, small changes in elevation will cause small changes in CAS. On the other hand, in high-angle fire, small changes in elevation will cause large changes in CAS. In a high-angle registration, the CAS determined at the initial elevation and applied throughout the mission will often differ substantially from the CAS corresponding to the adjusted elevation. This false CAS, when added to the angle of site, will produce a false site. To provide accurate data, the FDC must determine the true site and subtract it from the adjusted QE to compute the true adjusted elevation. To determine the true site, successive approximation is used.

b. The steps in Table 10-10 are used to determine the true site and true adjusted elevation.

10-39. DPICM High-Angle Registration

a. Conduct a registration with DPICM (M483A1) in the self-registration mode. This destroys the submunitions and causes the round to detonate like an HE round.

b. If terrain in the target and/or firing unit area requires using high-angle fire, a high-angle high-burst registration using the M577 time fuze can be conducted. (The M577 has a small probable error in height of burst in relation to the M564/M565 time fuze family. This type of registration is conducted with the DPICM projectile in the SR mode. The procedures are the same as for those in low-angle HB registration with the following exceptions:

(1) Add a minimum of 4 PEHB (DPICM TFT, Table G, Column 5) to the altitude of the orienting point.

(2) The fuze setting to fire in an HB high-angle registration is the fuze setting corresponding to elevation plus CAS. The CAS in high-angle fire is usually a relatively large negative number. To determine CAS, enter Table G of the TFT with the range to the nearest 500 meters and extract from Column 12 or 13 the CSF for a 1-mil angle of site. Multiply the angle of site by the CSF to determine CAS. Apply the CAS to the elevation determined from the high-angle GFT. Move the MHL over the value of elevation plus CAS, and read from the TF scale to the nearest 0.1 fuze setting increment.

(3) Determine drift and elevation from the high-angle GFT.

(4) Determine site by multiplying the 10-mil site factor corresponding to the adjusted elevation by the angle of site divided by 10.

c. Determine the adjusted elevation for a high-angle HB registration in the same manner as for a low-angle HB registration. Site is based on the altitude of the mean burst location.

d. Determine the adjusted time in the same manner as in a low-angle HB registration. To determine the total fuze correction, subtract the time corresponding to elevation plus CAS from the adjusted time. When firing with a GFT setting, apply the total fuze correction to the fuze setting corresponding to the adjusted elevation to determine the fuze setting to fire.


Section VI

Offset Registrations or Registrations to the Rear


The tactical situation may make registering from the unit location or along the primary azimuth of fire impractical. The offset registration or registration to the rear should reduce the vulnerability of the firing unit to detection by enemy counterbattery assets. Both of these registrations may require coordination for firing positions or known points. The registrations are conducted by using normal precision or HB/MPI registration procedures.

10-40. Offset Registration

a. An offset registration is conducted by one howitzer from a position away from the rest of the unit. The offset position must be coordinated to ensure there are no other friendly units in the area as the registration may draw enemy counterbattery fire. The offset position must be on common survey with the firing unit to ensure that any corrections for survey errors in the offset position are valid in the firing unit position.

b. Adjusted data and resulting corrections determined from the offset position are valid for that position within normal range and deflection transfer limits.

c. The registration corrections are based on the azimuth and range from the offset position to the known point. It is assumed that if a registration were conducted from the firing unit area by using the same range and azimuth (as from the offset position), the adjusted data and resulting corrections would be the same as those obtained in the offset position. (See Figure 10-20).

10-41. Registrations to the Rear

A registration to the rear (or along some other azimuth significantly different from the primary azimuth of fire) may be either a precision or an HB/MPI registration. The registration will result in corrections, but these corrections must be modified for the primary zone of fire by using the eight-direction met technique (Chapter 11). The actual area where the rounds will be bursting must be coordinated to ensure there are no friendly units in the area.


Section VII

Determination and Application of Registration Corrections


Registration corrections consist of a total range, total fuze, and total deflection correction. FDC personnel compute these corrections by comparing the chart or should hit data (the data that when fired under standard conditions will cause the round to burst at a point of known location) with the adjusted or did hit data (the data that when fired under nonstandard conditions will cause the round to burst at a point of known location).

10-42. Computation of Total Range Correction

a. If standard conditions existed, the elevation fired to achieve the chart range would be the elevation listed in the firing tables for that chart range. When nonstandard conditions exist the range that is achieved by firing a certain elevation is greater or less than the range listed in the firing tables by an amount equal to all of the effects caused by the nonstandard conditions. The difference is the total range correction.

b. The total range correction is the difference in meters between the initial chart range and the firing table range corresponding to the adjusted elevation. Determine the total range correction as follows:

(1) From the TFT or GFT, determine the range (to the nearest 10 meters) corresponding to the adjusted elevation.

(2) Subtract the initial chart range (or achieved range) from the range corresponding to the adjusted elevation. The result is the total range correction. The total range correction is always a signed value and is used in solving the concurrent met. See the following example.

10-43. Computation of Total Fuze Correction

a. The time portion of a precision or high-burst registration will result in an adjusted or did hit time (fuze setting). The time corresponding to the adjusted elevation is the should hit time that must be compared to the actual adjusted time determined by firing. The difference between the time corresponding to the adjusted elevation and the adjusted time is the total fuze correction (DHD - SHD = TOT).

b. To determine the total fuze correction, subtract the time corresponding to the adjusted elevation (or elevation plus CAS if the VI is greater than 100) from the adjusted time. The total fuze correction is always a signed value and is used in solving a concurrent met. See the following example.

10-44. Computation of Total Deflection Correction

a. The total deflection correction is the correction, in mils, that must be added to the chart deflection to correct for all nonstandard conditions.

b. To determine the total deflection correction, subtract the chart deflection from the adjusted deflection. The total deflection correction is used in solving the concurrent met technique, in processing immediate type fire missions, and for updating manual safety computations after a registration. For all other missions, the GFT DF correction plus drift is used.

c. A GFT deflection correction is determined by subtracting the drift corresponding to the adjusted elevation from the total deflection correction. The GFT deflection correction remains the same for all elevations fired with the registered charge. The drift is applied to the GFT deflection correction to determine the deflection correction to be used for that mission. Using the precision registration example in Figure 10-3, determine the total deflection correction as follows:

10-45. Determination of Total Registration Corrections

The computational space on DA Form 4757-R (Registration/Special Corrections Work Sheet) will be used to determine the total corrections. Use Table 10-12 to determine total registration corrections.

10-46. Low-Angle GFT Settings

a. The data determined from a registration must be applied to FDC graphical equipment. This will enable the unit to attack accurately located targets without adjustment (first round fire for effect) within transfer limits.

b. Listed below are the elements of a GFT setting. These elements are recorded in the lower computational space of the record of fire used to process the registration. Additionally, they may also be recorded on DA Form 4757-R and on the record of fire of a mission in which they are being used. For the HB/MPI registration, the GFT setting is recorded on DA Form 4201. The acronym UCARET is used as an aid in recording the GFT setting. It is used to keep the GFT setting preceding the total and GFT deflection corrections in order.

  • Unit that fired the registration.
  • Charge fired during the registration and the charge for which the GFT setting applies.
  • Ammunition lot used in the registration. With separate-loading ammunition, the first letter designates the projectile lot used during the registration. The second letter designates the propellant lot used during the registration.
  • Range (chart or achieved) from the howitzer to the point of known location.
  • Elevation (adjusted or did hit).
  • Time (adjusted or did hit fuze setting).
  • Total deflection correction (the difference between the adjusted deflection and the chart deflection).
  • GFT deflection correction (the difference between the total deflection correction and the drift corresponding to the adjusted elevation).

c. The following is an example of a completed GFT setting as it is written.

GFT 1/A CHG 4 LOT AG RG 4950 EL 314 TI 18.5

TOT DF CORR R1 GFT DF CORR R7

d. The following is an example of a completed GFT setting as it is written with total corrections.

10-47. Determination of a GFT Setting When the Registering Piece is not the Base Piece

It may not always be possible to register with the base piece. When a howitzer other than the base piece is used to register, corrections must be made to compensate for the displacement of the registering piece from the base piece. Use a DA Form 4757-R and the steps in Table 10-13 to determine the necessary corrections.

10-48. Construction of a GFT Setting

Once the information for the GFT setting has been determined and recorded on DA Form 4757-R, the GFT setting can be constructed on the GFT. Use the steps in Table 10-14 to construct a GFT setting on the GFT.

NOTE: An example of a one-plot GFT setting applied to a GFT is shown in figure 10-23.

10-49. Construction of a Two-Plot or Multiplot GFT Setting

The steps in Table 10-15 are used to construct a two-plot or multiplot GFT setting.

10-50. Update of a GFT Setting When Transferring From a Map Spot or Observed Firing Chart

a. Field artillery units must be able to deliver responsive, accurate fires immediately upon occupation of a new position. Firing must not be delayed because of lack of survey or suitable maps. An initial firing chart may be based on a map spot or an observed firing chart. Once the actual survey is brought into the unit's area, the firing charts must be reconstructed on the basis of the firing unit's true location and true azimuth. GFT settings based on map spot or observed fire charts are accurate but must be updated.

b. When a registration is conducted on the basis of the map spot data for the registration point and/or firing unit location, the corrections determined will include corrections for map spot errors and possible human errors in plotting the locations. Once survey data are available, the GFT setting(s) determined must be updated to account for the initial inaccuracies.

c. Once survey data become available, the HCO will construct and plot the locations on a surveyed firing chart. He will determine a new chart range and deflection to the known point. The new chart range will be the range for the GFT setting. The VCO will use the new chart range and an updated VI to recompute site. The computer will recompute the adjusted elevation and new total and GFT deflection corrections. The adjusted fuze setting was determined by firing and will not change. Use Table 10-16 to update a GFT setting when transferring from a map spot or observed firing chart to a surveyed firing chart.

10-51. Registration Transfer Limits

a. In manual gunnery techniques, the total corrections determined from a registration are valid only within certain range and deflection transfer limits. Transfer limits define the ranges and deflections within which the GFT setting is expected to produce accurate firing data. The total corrections for nonstandard conditions are valid only when the weapons are firing toward the known point. For example, when weapons are firing on a different azimuth than that of the known point, the wind will not affect the round in the same manner as it did along the azimuth to the known point.

b. Range Transfer Limits.

(1) The range transfer limits for a one-plot GFT setting are shown on the GFT corresponding to the red numbered elevations.

(2) The range transfer limits for a two-plot GFT setting are between the two ranges used to apply the GFT setting(s). This type of GFT setting becomes less accurate outside these two ranges.

(3) The range transfer limits for a multiplot GFT setting are eliminated when three or more sets of corrections are available for the same charge. The optimum multiplot GFT setting reflects a plot for each met line number that the charge may cause the projectile to pass through (met check gauge points).

c. Deflection Transfer Limits.

(1) The total registration corrections are valid only within certain deflection transfer limits.

(2) When the chart range to a target is 10,000 meters or less, the total corrections are valid within an area 400 mils left and 400 mils right of a line between the unit and the known point (mean burst location) (Figure 10-24).

(3) When the chart range to a target is less than 10,000 meters, the total corrections are valid within an area 400 mils left and 400 mils right of a line between the unit and the known point (mean burst location) out to 10,000 meters, and 4,000 meters left and 4,000 meters right of the line for ranges beyond 10,000 meters. (See Figure 10-25.)

(4) Total registration corrections may be determined throughout the entire 6,400 mils around the firing unit by using the eight-direction met technique (Chapter 11).

10-52. High-Angle GFT Settings

a. GFT settings for high-angle fire are written in the same manner as those for low-angle fire. An example is shown below.

GFT 1/A, Chg 3, Lot AG, Rg 4970, EI 1111

Tot Df Corr L32 GFT Df Corr R20

b. The high-angle GFT setting is constructed on the GFT by placing the MHL over the adjusted elevation for the charge fired and drawing a range gauge line through the GFT setting range on the range scale parallel to the MHL. The MHL becomes the elevation gauge line, and all data except for range and 100/R are read under the MHL. The GFT deflection correction and charge are recorded on the cursor.

10-53. High-Angle Transfer Limits

Standard range transfer limits are not applicable to high-angle fire because the range span of each charge is so short. Corrections in the form of GFT settings and GFT deflection corrections are considered valid for the charge used in determining the corrections and are also considered valid for other charges as shown in Table 10-17.

10-54. Transfer of GFT Settings

a. When only one unit of a battalion equipped with weapons for which the same firing tables are used is allowed to register, the GFT setting determined by the registering unit maybe transferred to the nonregistering units in the absence of better information.

b. Transferring of GFT settings should only occur if a concurrent met technique cannot be performed and position constants cannot be isolated (Chapter 11). To transfer a GFT setting, certain conditions must exist as follows:

  • Common survey between positions.
  • Azimuth of fire (octant) are the same.
  • Ability to correct for MVVs for the registered lot.

c. The distance over which the GFT settings are transferred should be monitored closely. The further from the registration point the GFT setting is transferred, the less accurate the GFT setting will be. This is due to the different effects of the met (weather) conditions. The guidance given in chapter 11 on the validity of met messages should be used when transferring GFT settings.

d. The procedures for determining a GFT setting for a nonregistering unit is listed in Table 10-18 below. The registering unit must send the GFT setting and registering piece MVV to the nonregistering unit.

10-55. Example of Transferring a GFT Setting

Battery A, 1st Platoon registered, and Battery C, 1st Platoon wants the GFT setting transferred to their unit. Battery A, 1st Platoon registered with their base piece which has an MVV of -1.6 m/s. The base piece for Battery C, 1st Platoon has an MVV of -7.7 m/s.




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