DBPapers
DOI: 10.5593/SGEM2014/B22/S9.050

PROJ.4 CARTOGRAPHIC PROJECTION LIBRARY AS 3D TRANSFORMATION TOOL IN CZECH CONTEXT

M. Seidl, P. Trasak
Wednesday 1 October 2014 by Libadmin2014

References: 14th International Multidisciplinary Scientific GeoConference SGEM 2014, www.sgem.org, SGEM2014 Conference Proceedings, ISBN 978-619-7105-11-7 / ISSN 1314-2704, June 19-25, 2014, Book 2, Vol. 2, 395-402 pp

ABSTRACT
Coordinate transformation is the fundamental problem in geodesy. The PROJ.4 cartographic projection library together with EPSG geodetic parameters dataset is well known for its ability to transform coordinates across national coordinates systems mainly for GIS purposes. This paper focuses on PROJ.4 ability to transform coordinates with higher precision required by practical land surveyors. The whole task is solved in context of Czech Republic. This means we face up to the problem of Uniform Trigonometric Cadastral Network (S-JTSK) distortion, new system S-JTSK05 and vertical system of Baltic Sea Datum (Bpv). The issue was treated by implementation transformation based on original Krovak projection together with horizontal and vertical correction grids. The precision of transformation defined by this PROJ.4 string cs2cs +proj=lonlat +ellps=GRS80 +towgs84=0,0,0 +to +proj=krovak +ellps=bessel +nadgrids=etrs-jtsk_v1202 +geoidgrids=etrs-bpv_v1005 with two correction grids one for horizontal and one for height correction can be expressed by these mean values and standard definitions. The mean values for dx, dy and dz are -0.004, 0.007 and 0.003 m and corresponding standard deviations are 0.003, 0.006 and 0.008 m. This precision is close to requirements of Czech Office for Surveying, Mapping and Cadastre but does not fully satisfy its criteria. The new unofficial S-JTSK05 system with Modified Krovak projection had to be implemented to compute horizontal correction grid of S-JTSK.

Keywords: proj.4, coordinate transformation, JTSK, Bpv, Krovak