Convert Map Images to GeoTiff

Then I found the GPS utilities module in QGIS (in the menu) and hooked up my Garmin eTrex Summit and downloaded everything in it. The waypoints, tracks and routes all filled in the detail of our farm.

I had to install gpsbabel as indicated in the gps download dialogue: sudo apt-get install gpsbabel

Then I tried the raster layer thing: First, convert the .jpg image of the orthophoto I scanned in, to GeoTiff:

sudo apt-get install gdal-bin gdal_translate -a_ullr 18.5230 -32.6970 18.6000 -32.7760 20000917b.jpg 20000917b.tif

(No, I didn't just smoke my socks then know this. I spent ages (Ok, 1hr or so) googling and reading the gdal website before I worked this out. The coordinates are more or less the area covering the farm and correspond to the top left and lower right corners of the image)

Then I open the raster layer in QGIS and there is the image. Now, the coordinates I used a rather roughly estimated, so the track I made driving on the road does not overlay exactly with the road in the image, and that is a calibration thing. However, I am hoping to get the GeoTiffs from CD:SM all properly calibrated etc so that problem might be solved.

Conversion Process for SID Files

The 1:250 000 maps from Surveys and Mapping are in Mr. Sid format (a proprietary compression format unfortunately). To get one of these maps off the CD do work as a raster layer in QGIS, follow these steps:

1. mrsiddecode -i wgs_3318.sid -o wgs_3318.jpg

(this outputs the x and y scale that are important to note)

1. gdal_translate -a_ullr 17.829361 -33.000131 18.9 -35.00434 wgs_3318.jpg wgs_3318.tif

Now you load the raster layer, and check its properties. The X and Y scale values are listed in the metadata. If they do not match what mrsiddecode gave, then you need to scale the 'lower right' coordinates proportionally until they do.