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Military

CHAPTER 1

POSITION/NAVIGATION (POS/NAV)


The Global Positioning System (GPS) is a satellite-based positioning system developed by the DoD for determining highly accurate earth positional information. GPS supported a wide variety of applications from large unit maneuvers to individual soldiers navigating their way through the desert. The unfamiliar and generally featureless terrain in the Kuwaiti Theater of Operations increased the need for reliable POS/NAV information. Units used GPS receivers to plot their objectives and movements toward those objectives. GPS receivers were used to relocate tactical operations centers. Special Forces units used GPS receivers to accurately determine their positions while operating in enemy territory. Forward observers used the devices to more accurately target enemy forces and to direct friendly fire. Signal personnel used the small, lightweight, GPS receivers (SLGRs) (pronounced "sluggers") for both navigation and positioning of communications equipment.

The system consists of space and user segments which combine to provide up to 10- meter positioning accuracy in two and three dimensions (latitude,longitude, military grid reference system, etc.).

SPACE SEGMENT: A constellation of 24 satellites will make up the complete space segment of GPS when the complete constellation of satellites is in place in mid 1993. During Operation DESERT STORM, there were 16 usable satellites (experimental and operational) providing approximately 24 hours of two- dimensional coverage and 19 hours of three- dimensional coverage of the Theater. Two- dimensional location determination requires input to the receiver from at least three satellites. Three-dimensional location requires input from four satellites. When the entire constellation is in place, every point on the earth will be in view of six satellites.

Figure 1. GPS Satellite Constellation

USER SEGMENT: A number of receivers comprised the available user segment of the GPS at the start of Operation DESERT SHIELD. The two primary categories of receivers available during Operation DESERT STORM were the manpack/vehicular (M/V) models and the SLGRs. A small number of GPS receivers were integrated into aircraft and seacraft. The M/V receivers used were the AN-PSN8s and the AN-PSN9s. These receivers weigh between 10 and 20 pounds and can receive the precision-coded signals from the GPS satellites that result in close to 10-meter positioning accuracies. The M/Vs were primarily used in a vehicle-mounted mode. The Army owned approximately 500 demonstration SLGRs at the outset of Operation DESERT SHIELD. These sets had been used in a number of training exercises to help determine the applications and capabilities tactical forces would need from a small handheld device.

Figure 2. Small, Lightweight GPS Receiver (SLGR)

These SLGRs were commercial sets that received the course acquisition signal from the GPS satellites. In normal operations, this course acquisition signal is transmitted with a varying degree of error to deny precise navigational information to potential threats. For Operations DESERT SHIELD and DESERT STORM, the course acquisition signal was transmitted without error ensuring the best possible accuracy for the commercial receivers (15- to 30-meter accuracy).

NOTE: The Army is developing a small GPS receiver that uses the precision signal from the satellites. This device was previously known as the Precision Lightweight GPS Receiver (PLGR) and will now be known as the Lightweight Army User Equipment (LAUE).

The demonstration SLGRs were collected and distributed to deploying contingency forces in August 1990. Deployment of follow-on units required the purchase of an additional 7,000 SLGRs. The actual allocation of these devices was left to the discretion of the division commanders.

Quantities distributed (approximate):

  • SLGRs (all types) - 4,000
  • AN-PSN8/9s - 550
  • Integrated Packages (built into aircraft/seacraft) - 100

OBSERVATION: There were not enough GPS receivers available to cover all the applications for which they could have been used.

DISCUSSION: Comments received from GPS users did not generally relate to system problems but to the fact that there were not enough receivers to go to all of the users who wanted them. The Army DCSOPS understood this and began procurement actions for approximately 7,500 GPS receivers. The short duration of the war and the limited production and delivery capability of the commercial vendors resulted in fewer GPS receivers being available to the soldiers in the field. The distribution of SLGRs was left to the receiving units, based on a Theater Army distribution plan. The only receivers available to some infantry brigades were with Air Force or fire support elements. These elements were often used to accompany vehicular reconnaissance just to provide GPS support. Field artillery units distributed GPS receivers down to battery level. With only one receiver available at battery level, the battery commander had to decide whether to use the receiver as a navigation tool or a survey control tool.

LESSON(S): The Army must review its GPS receiver requirements in light of the Operation DESERT STORM experience and identify all users. Procurement of GPS receivers should be expedited where possible to ensure that this capability is more widely available for future Army contingencies.

Commanders must carefully consider where and how available GPS receivers are to be used.

OBSERVATION:The GPS aided Field Artillery survey by providing a third-order control network in Theater and by locating firing sites.

DISCUSSION: Prior to the onset of hostilities, engineer survey units used commercial geodetic survey receivers to establish a third-order control network in northern Saudi Arabia. The survey units extended this network into Iraq after ground actions began.

During the ground operations, standard methods of field artillery survey could not be maintained as maneuver units rapidly traversed terrain. Battery commanders kept control of the field artillery survey requirements using the GPS receivers for positioning. The firing batteries used a compass for azimuth.

LESSON(S): GPS receivers can be used in combination with other field Artillery positioning equipment to provide expedient position updates.

Requirements for geodetic control need to be reviewed and compared to capabilities of evolving GPSs.

Engineer survey teams need to be equipped with, and trained on, geodetic quality GPS receivers. This will ensure survey networks can be established on remote, austere battlefields.

OBSERVATION:Most of the recipients of the SLGRs had no formal training on the use of the device.

DISCUSSION: Other than a few units that had been exposed to the SLGRs through the demonstration program, most units receiving these pieces of equipment had no prior training or experience. A team of trainers from the Army's space community traveled to deployment sites in early August 1990 for the purpose of conducting ``train-the-trainer'' exercises.

This training coincided with the distribution of the SLGRs to the units. As more units deployed to the Gulf, this train-the-trainer effort could not be sustained. A SLGR training support package was prepared for delivery to units receiving the SLGRs. This enabled units to conduct training after arrival in theater. Distribution of these training packages was limited by competing demands for other critical supplies, reducing their effectiveness as a training tool. The SLGRs came equipped with contractor-supplied user manuals. These manuals provided the necessary operational information required by users but were not set up for use as training guides. Training packages did not accompany each of the SLGRs, but were distributed to Theater SLGR representatives and Army Space personnel for use as guides to training.

Lack of formal training resulted in some misunderstandings of GPS capabilities. Some users thought the receivers were more accurate than they really were, and others thought that the receivers worked only in particular parts of the world.

LESSON(S): Delivery of new systems, such as the SLGR, during operations requires diligent efforts to train the users. This effort must come from outside the operational units and training must be conducted in as least a disrupting fashion as possible. In the case of SLGR, train the trainer proved to be very useful prior to deployment of the initial contingency forces. Simple step-by-step training guides should be delivered with the equipment after units have deployed.

GPS must be included or integrated into land navigation training conducted at NCO and Officer basic leadership courses. This training must include a solid review of system capabilities. This effort has already begun in some schools' programs of instruction.

Figure 3. GPS Satellite

Table of Contents
Foreword
Chapter 2: The Battlefield Environment



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