Georeference an Image

RobertEllis1

I have control point on a png image and I want to georeferenced it in UTM. I know the coordinates in UTM of the control points. I don't find the help instructions clear for the warp tool under coordinates\georeferenced. 1) I don't really want to warp it so I don't understand identify a new and old point, 2) I can't see where to put in the actual coordinate of a control point. Maybe I'm using the wrong tool but I can't find anything else. Some guidance would be appreciated.

BeckyBodger

Hi @RobertEllis1 Warping is the Geosoft name for Georeferencing. I find the easiest way is to use the semi-interactive option, and at the end I like to attach the warp to a grid rather than create a new warped file since it doesn't change the resolution of the original image.

1. Display the image on a map:
Map > Import > Image > Use default registration.

2. Create your warp file:
Coordinates > Georeferencing > Define a Warp.
Enter a name for your warp file
Pick what sort of warp you will create (I find using 4 control points works best, one in each corner).
Select Semi-Interactive.

3. Define your coordinate system for the new georeferenced image.

4. Click on the control point on your map and it will give you the current XY location for you and you enter the new real world coordinate for that point.

5. Click Next and click the next control point.
Never cross points, I start in the top left hand corner and move clockwise around the image.

Once that's done, you have a warp file that can be attached to the original image. You then have to keep the original png and new *.wrp file together in the same folder.

1. Coordinates > Georeferencing > Attach warp to a grid.

These are slightly modified steps from the following Knowledge Base Article:

https://my.geosoft.com/supportcentre#/kb/kA330000000V1ftCAC

I hope that helps!