Coordinate calculation |
|
|
Rectangular coordinates (XYH) pay off in two systems of coordinates - system of 1942 and system UTM. Geodetic coordinates (BLH) are considered in system of 1942, system WGS-84 and ПЗ-90. For geodetic coordinates the following formats of display are stipulated: - Radians; - Degrees; - Degrees, minutes, seconds; - Degrees, minutes, seconds, a hemisphere.
Initial values of coordinates in dialogue windows are coordinates of the current point on a map . After data input into any window of dialogue and Update keystroke a recalculation of coordinates in all systems takes place. The Show current point button serves for display of coordinates values of the current point at change of its position on a map. The Show button is intended for map redrawing if new coordinates values of a point are entered.
To recalculate the orthometric height relative to the geoid (MSL is the mean sea level) to the geodetic height relative to the surface of the spheroid WGS 84 and vice versa, MTW format matrices containing the geoid model EGM2008 are used. For obtaining the geodesic height, the correction obtained from the EGM matrix according to the coordinates of the point, taking into account the interpolation of the value over the nearest elements of the matrix, is added to the orthometric height. The corrections from the EGM matrix with a step of 1 minute differ from the corrections from the EGM matrix with a step of 2.5 minutes on the average on 30-60 cm when using interpolation algorithms. The range of corrections is approximately from -107 meters up to +86 meters. The value of the orthometric height does not depend on the coordinate system, projection parameters, and other properties of the cartographic image. The value of the geodetic height depends on the parameters of the spheroid relative to which it is measured (WGS 84, PZ-90.11, Krasovsky 1940, and so on). To go from the orthometric height to the geodetic height of PZ-90.11, the conversion to the geodesic height of WGS 84 is performed according to the EGM2008 model, and then the conversion, taking into account the parameters of GOST 32457-2017, to PZ-90.11. The normal height (for example, the height in the Baltic system of heights relative to the quasigeoid) differs from the orthometric height from tens of centimeters in the flat areas to several meters in the mountain areas. For practical calculations, instead of the normal height, an orthometric height can be used. The name of the EGM matrix used for calculating heights is indicated in the header of the dialog. The GIS installation includes a matrix in increments of 2.5 minutes. A more accurate matrix can be downloaded at https://gisinfo.ru/price/price_map.htm and replaced in the folder with the installed GIS. Earth's Gravity Model (EGM2008) is a geopotential model made up from coefficients of spherical harmonics published by the Geomatics Department of the National Geospatial Intelligence Agency (NGA). NGA provides the model in two formats: in a raster (matrix) image that stores the height of the geoid relative to the surface of the WGS 84 spheroid for each coordinate at a given resolution, or in a format that provides numerical parameters - coefficients - that determine the model.
|
Dialogue is intended for recalculation of coordinates.