DBPapers

VERIFICATION OF GEODETIC POINTS USING GPS MEASUREMENTS

AUTHOR/S: J. SABOVA, V. JAKUB
Sunday 1 August 2010 by Libadmin2005

5th International Scientific Conference - SGEM2005, www.sgem.org, SGEM2005 Conference Proceedings/ ISBN: 954-918181-2, June 13-17, 2005, 615- 620pp

ABSTRACT

The good functionality (applicability) of a geodetic point can be characterized by
its compatibility. Compatibility of a geodetic point can be defined by the 2D or 3D
geometric coincidence between (Jakub 2001, Jakub-Sabova 2004):
a) the immaterial point given by coordinates for a geodetic point in a reference
frame;
b) the material point defined by the physical mark of this geodetic point.
These two points should be geometrically identical in horizontal plane (2D) or
space position (3D). They have but really different (non-coincidence) relations at each
geodetic point. The reliable differences between the both positions a), b) can be
expressed by the coordinate differences (discrepancies) dC=C´-C i.e. [dX dY dZ]=
[X´Y´Z´]-[XYZ] between the point coordinates C from the database and from the
present measurements C´.The differences dC at points can reach values from some mm
up to unacceptable values of some cm. In the contemporary geodetic networks (epoch
t´) there are always some points which do not already fulfil the compatibility
requirements. This is typical above all for the networks established and concentrated in
the past (epoch t). Point uncompatibility, that indicates properly its inapplicability in the
present, can be caused e.g. owing to unaccurate coordinate determination in epoch
t, point carrier movements in the period t´- t, various datum influences and other
causes. It is therefore necessary always to verify all the "given" points before their use
in the present geodetic activities and to employ the compatible points only.
The use of incompatible points in a network adjustment causes a lot of biased
coordinate estimates whose identification in the results represents a cumbersome and
uncertain task that has any unified methodical solution.