How To: Warp or Geo-reference a Grid or a Database

Problem/Symptom:
I have a grid or a database in local XY/Lat,Long coordinates, and wish to geo-reference these to real, projected XY (or geographic Lat,Long) coordinates. Or, I wish to transform/change the coordinates of a grid or database. Or, I have imported an image but it has no coordinates. I wish to geo-reference these so that I can overlay the image on a projected map.

Environment:
Applies to all versions of Oasis Montaj and Target. This particular resolution refers to the steps involved in Oasis Montaj and Target v7.0.

Resolution:

In v6.4.*, this is called Warping. In v7.0 it is also referred to as Geo-referencing.

Method A) How to geo-reference a grid or image

1) Display/import your image or grid to a new map.

2) With the map selected, go to Coordinates > Georeferencing > Define a Warp (warpfile.gx).

3) If you have multiple points you can correlate, use the 4-Point Quadrilateral Warp. If you only have a couple of points, use 2-Point or 3-Point.

4) The best bet is to use Semi-Interactive for the Definition Mode.

5) You can then define the output coordinate projection.

6) Then proceed, in a clockwise or counter-clockwise fashion only, to click on the corners of your grid/image. You are shown the current XY, and you need to manually enter the new XY values you would like this point to be. When finished (all points), click Finish.

7) This will produce a *.WRP file. This is a simple text file that you can manually edit in a text editor.

8) Then go to Coordinates > Georeferencing > Warp a Grid (warpgrid.gx).

9) Choose the grid or image file you are warping, and the *.wrp file.

10) For new warped grid file, make sure to browse for and choose the appropriate file type to save as. If you are warping a GRD, use Geosoft default *.grd. If you are warping an Image, use Geosoft Color *.grd or Geotiff colour *.tif.

Note - If you are warping an image and do not choose to save as file type Geosoft Color *.grd or Geotiff colour *.tif, your resulting grid/image will have wierd colours.

11) Once complete, display your new grid/image to a map.

Method B) How to geo-reference a database

1) In order to warp properly, you should create a new map and base map from your database (*.gdb).

2) On the new map, follow the steps 2 to 7 above.

3) Now go to Coordinates > Georeferencing > Warp Data (warpdata.gx).

4) Choose your current XY, and the WRP file, and two new channels that will be calculated from the warp file.

5) Once complete, your GDB will contain two new channels. To use this for gridding and mapping, make sure they are the current X and current Y channels by going to Coordinates > Set Current X,Y,Z Coordinates (xyset.gx). If you set a projection for your GDB, you can also set the current XYZ channels this way.