Calibrating a Raster Map

If you have a decent paper or electronic (PDF, JPG, GIF, etc.) map that's in the proper scale (ie not sketched out by someone from your snowmobile club 20 years ago), you can use it to make a GPS map by tracing over the lines on it. If you have a map ready to use, save it as a Bitmap (BMP) and read on.

First you have to calibrate it. You'll need to know the exact coordinates of two points on your map, preferably far apart from each other. Two diagonally opposite corners are best. To get these coordinates, you could use another source to find the coordinates at an intersection or other easily identifiable spot on the map.

Run OziExplorer, do "File > Load and Calibrate Map Image" and select your image. Click on the "Point 1" tab on the right, and then click on one of the spots on the map that you know the coordinates for. Now type in those coordinates on the right side of the screen. Now click on the "Point 2" tab and do the same thing for the second known point.

Be as exact as you can here. The accuracy of these points determines the accuracy of your final map.

Now click the save button and save your .mp file. This saves your calibrated map in "Polish" format, which can be opened directly in MapEdit.

You have just calibrated your map!