Leica Geosystems GPS System 500 - Technical Reference Manual - Manual (Page 274)

274 11. Applications Technical Reference Manual-4.0.0en
For cases where there is no
information regarding the ellipsoid
and/or map projection and/or you wish
to force the GPS measurements to tie
in with local existing control then the
One Step approach may be the most
suitable.
The 2-Step approach takes the local
ellipsoid and map projection into
account and can therefore be used for
larger areas than 1-Step trans-
formations. Compared to the
Classical 3D approach it treats
position and height information
separately, which allows for position
only control points to be used as well.
In order to determine a Coordinate
System, you will require the
coordinates of points in both the
WGS84 and local coordinate system.
Depending on the type of
transformation you wish to use, you
may also need details of the map
projection, local ellipsoid and a local
geoidal model program.
1. 3D Helmert Transformation:
Ellipsoid and Projection must be
known, Geoid information is optional.
2. 1-Step Transformation: Geoid
information is optional, no other
information is required.
3. 2-Step Transformation: Ellipsoid,
Projection and a Pre-transformation
must be known, Geoid information is
optional.
From the Application Menu, select
Determine Coord System and press
CONT (F1).
Coord Sys - Type in a new name for
the new coordinate system.
WGS84 Pts - Select the Job from
which the points with WGS84
coordinates will be taken.
Local Pts - Select the Job or ASCII
file from which the points with local
coordinates will be taken.
Use LOCAL (F4) to define the source
of the local coordinates (from Job or
ASCII).