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Bogdan Morosanu edited this page Mar 18, 2021 · 2 revisions

Pytransdatro Wiki

Pytransdatro is a Python library which can be used for the coordinate transformation between ETRS89 and Stereo70 coordinate reference systems (CRSs).

Pytransdatro implements the official algorithm published by the Romanian National Agency for Cadastre and Land Registration, Department of Geodesy and Cartography, Geodetic Service.

The transformation is reversible and done in 3 (4 if height/elevation included) steps:

(Lat, Lon[, h])ETRS89 [<- 1 -> (Lat, Lon[, h])ETRS89 + MN75] <- 2 -> (N, E)StereoGRS80 <- 3 -> (N, E)Stereo70' <- 4 -> (N, E[, H])Stereo70[ + MN75], where:

  • [...] = optional
  • <-n-> = nth step
  • Lat = latitude
  • Lon = longitude
  • N = northing
  • E = easting
  • h = ellipsoid height
  • H = normal height

The above steps are described below:

  1. Projection of ETRS89 ellipsoidal coordinates (GRS80 ellipsoid) to oblique stereographic grid coordinates. Projection defined by the following parameters:

    • false northing = 500,000
    • false easting = 500,000
    • latitude of origin = 46°
    • central meridian = 25°
    • scale factor = 0.99975

  2. Two-dimensional Helmert transformation between oblique stereographic projection on GRS80 (Geodetic Reference System 1980) ellipsoid and oblique stereographic projection on SK-42 (Krassowsky 1940) ellipsoid. The transformation parameters are defined below (unit of measurement was preserved to reflect the definition from the official algorithm):

    • translation on north = -31.8051
    • translation on east = -119.7358
    • scale factor = -0.11559991, ppm (parts per milion) value
    • rotation = 00° 00' 0.22739706'', degrees, minutes, seconds value

    They are used as defined for the transformation 4 -> 1 and with their sign reversed for the transformation 1 -> 4.

  3. Corrections applied to the grid coordinates based on interpolated (bicubic spline) values obtained from a predefined grid.

  4. Transformation of height/elevation based on interpolated (bicubic spline) values obtained from a predefined grid. This is basically a tramnsformation between ETRS89 ellipsoid height and Marea Neagra 1975 normal height

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