This is the terrain geometric distance from the length of the geodesic line on the ellipsoid surface defined by the projection of end points in accordance with it geodesic vertical elements.
The distance reduction is usually carried out in two steps:
1. Conversion of the geometric distance, Dg, to the ellipsoid string distance, Dce
expression involving the ellipsoidal altitudes of the ends, h= H + N (where H is the orthometric height and N the geoid undulation) and where the geodesic line is approached by a circumference arch. The radius adopted for said arc is usually that corresponding to the mean of the Euler radius on normal mutual sections, though it an approximate the arithmetic mean of the mean Gauss radius, Rm,
where it is necessary to calculate the main radii of curvature of the ellipsoid at the ends of the line
2. Conversion of the ellipsoid string distance, Dce, to the ellipsoid arc distance, Dae
This final step will not affect the measurement for short distances.
García-Asenjo, L., Hernández, D. & Llácer, C. (2004). Study about the influence of geodesic corrections on topographic works carried out as from classical measurements and GPS. 8th National Topography and Mapping Congress TOPCART2004.
TcpMDT
