SURVEY STANDARDS AND SPECIFICATIONS
*This appendix implements STANAG 2934 and QSTAG 269.
The US government makes nationwide surveys, maps, and charts of various kinds that must be referenced to national datums. These are necessary for the conduct of public business, for national defense, and for development of the country.
a. Geodetic surveys, executed with high precision, are used to control mapping and charting operations and engineering projects. The terms geodetic survey and control survey are almost interchangeable.
b. Control surveys are of two types--horizontal and vertical. Horizontal control surveys determine latitudes and longitudes referenced to a national datum and provide the basis for rectangular coordinate systems. Horizontal geodetic surveys are adjusted to the mathematical figure of the earth applicable to the national datum. Vertical control surveys determine elevations to a national datum that has been referenced to tidal measurements. Vertical geodetic surveys are adjusted with respect to the geoid. These surveys provide permanently marked and properly described stations.
c. Horizontal control is established by triangulation, trilateration, and traverse procedures. Vertical control is established by leveling of a high order of accuracy.
d. The classifications and standards of geodetic control surveys in the United States are issued by the Federal Geodetic Control Committee (FGCC) under the authority of the Office of Management and Budget (OMB). The specifications are published in a document titled Classification, Standards of Accuracy and General Specifications of Geodetic Control Surveys and in a supporting document titled Specifications to Support Classifications, Standards of Accuracy, and General Specifications of Geodetic Control Surveys. Both documents are published by and can be obtained from the National Geodetic Survey Division, National Oceanic and Atmospheric Administration (NOAA), Rockville, Maryland 20852.
a. Field artillery control surveys are performed to fourth- and fifth-order specifications as described below.
(1) Fourth-order survey is FA survey performed to an accuracy of 1 unit of error in 3,000 similar units of survey. It usually is written 1:3,000.
(2) Fourth-order astro azimuth is an FA azimuth established by astronomical methods, the probable error of the result of which does not exceed 0.060 mil. The considered accuracy for FA survey is 0.150 mil.
(3) Fourth-order azimuth is an azimuth of a line used in the extension of fourth-order survey that, from its point of origin at a fourth-order astro azimuth line or higher-order direction, has depreciated in accuracy by a PE value of 0.030 mil per main scheme angle; or it is the azimuth of a line determined by computation between a fourth-order SCP and an SCP of equal or higher order. In the latter case, considered accuracy for FA survey is 0.300 mil.
(4) Fifth-order survey is FA survey performed to an accuracy of a maximum of 1 unit of error in 1,000 similar units of survey. It usually is written 1:1,000.
(5) Fifth-order astro azimuth is an FA azimuth established by astronomical methods, the probable error of the result of which does not exceed 0.12 mil. The considered accuracy for FA survey is 0.300 mil.
(6) Fifth-order azimuth is an azimuth of a line used in the extension of fifth-order survey which, from its point of origin, has depreciated in accuracy by a PE value of 0.09 mil per main scheme angle. A fifth-order azimuth cannot be obtained by computation between a fifth-order SCP and an SCP of equal or higher order.
b. The specifications presented in Tables B-1, B-2, and B-3 are the permissible tolerances allowed to ensure that the overall standards for fourth- and fifth-order surveys are achieved. The specifications apply for determining a 1:500 azimuth. If direction is not extended from the line established by observation, the rejection limit can be relaxed to 1.0 mil with a considered accuracy of 1.0 mil. In the tables, D/R means direct/reverse. In Tables B-1 and B-2, N represents the number of main scheme angles used to carry azimuth. In Table B-1, K represents the total main scheme distance surveyed to the nearest 0.1 kilometer. In Table B-2, K is the sum of the sides used to compute coordinates. When a computer or calculator is used, angles and distances may be used in computations to the nearest 0.001.
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