Gtransform

Modify|Gtransform

Gtrans is a third party software package that can be implemented into Topocad and used to transform known parameters between some systems. Systems can be set up.

New transformation relations (.tf and .tfi transformation information files) adds to the selected relation catalogue. The dialogue also shows a description of selected relation.

The procedure is as follows:

Select the objects you want to transform.
Go to Modify|Gtransform.
Select the system you want to start from.
Select the system you want to go to.
Select whether you want the transformation to create a new file (recommended).

A .tf file looks like this:

Geoid model

To use a grid file for your geoid you need to define this grid file in the geoid.def file that should be placed in the same directory as the transformation files. (tf- och tfi-files.)

Example:

GEOID       SWEN 01L grid
Geoidhöjdsmodell för SWEREF 99,
bilinjär interpolation i grid swen01l.grd, geografiska lat long
Gridstorlek: 601x301
lat-min: 55°      long-min: 10°
lat-max: 70°      long-max: 25°
dlat:     0°.025   dlong:     0°.05/
ELLIPSOID       GRS 1980/
GRIDSYSTEM      SWEREF 99 lat long/
HSYSTEM         RH 70/
GRIDFIL         swen01l.grd/
GEOID       SWEN05_RH2000 grid
Geoidhöjdsmodell för SWEREF 99,
bilinjär interpolation i SWEN05_RH2000.grd, geografiska lat long
Gridstorlek: 601x301
lat-min: 55°      long-min: 10°
lat-max: 70°      long-max: 25°
dlat:     0°.025   dlong:     0°.05/
ELLIPSOID       GRS 1980/
GRIDSYSTEM      SWEREF 99 lat long/
HSYSTEM         RH 2000/
GRIDFIL         SWEN05_RH2000.grd/
GEOID      RN 92 grid
Geoidhöjdsmodell för RR 92, RT 90 och RH 70,
bilinjär interpolation i grid RN92.GRD
xmin: 6100000     ymin: 1200000
xmax: 7700000     ymax: 1900000
dx:      5000     dy:      5000/
ELLIPSOID BESSEL/
GRIDSYSTEM RT 90 2.5 gon V 0:-15/
HSYSTEM    RH 70/
GRIDFIL    rn92.grd/
GEOID      RN 92 polynom
Geoidhöjdsmodell för RR 92, RT 90 och RH 70,
POLYNOM gradtal 3/
ELLIPSOID BESSEL/
GRIDSYSTEM RT 90 2.5 gon V 0:-15/
HSYSTEM    RH 70/
POLYNOM    3                1000000
        6881500.000      1535000.000
             -1.495           13.971
            -35.508           17.798
              1.161            5.807
            -11.195           38.700
             -7.616            2.246/