Grid, Analytic

a local geodetic grid. Analytic grids are set up by triangulation and trilateration on the basis of points of a state geodetic grid in order to perform large-scale surveys and facilitate engineering geodetic work.

First-order analytic grids are constructed in the form of solid grids, chains of triangles with no more than 15 points and angles not less than 30°, and systems or individual points based on geodetic grids of classes 1, 2, 3, and 4. The length of the sides is 2–5 km, the mean quadratic error of angle measurement m = 5″, and the linear displacement corresponding to the error of angle measurement τ = 5–12.5 cm. Second-order analytic grids are constructed analogously to first-order grids on the basis of points of geodetic grids of classes 1,2,3, and 4, a first-order analytic grid, and highly precise polygonometry. The length of the sides is 0.5–3 km, m = 10″, and τ = 2.5–15 cm.

In the absence of points of a state geodetic grid to substantiate surveys of the earth's surface and open excavations, independent first- and second-order analytic grids are constructed. For such grids, the area of the survey does not exceed 500 sq km on a scale of 1:5,000, or 100 sq km on a scale of 1 : 2,000.