Realigning misplaced GeoTIFF

Question

I have bought a few (30) GeoTiff maps from my country's Geo-department - South Africa. They all have a date in the filename and the newest one was created in 2004, I see one is dated 1977 - that old! Anyway, they came with a .tfw file each. When I simply copy these into Google Earth, or use MapTiler to create a default-settings WSG84 tile set, the map is unaligned. Meaning that they are really close to their correct positions but a bit off center and the deviation from supposed-position differs everywhere on the image/map.

Either the maps are wrongly geo-tagged or I use the wrong formats. I have no clue or experience with maps and their types (WSG84/UTM etc). I need to convert these maps into tiles for my iPhone app.

I have also tried using maps of USA and they worked and were outputted perfectly.

All I can tell about these maps is:

• It is a big white block with the map inside and the key/legend on the sides/bottom.
• The map inside has an arced top and bottom and sides/longitude-lines are skew.

I would like to think it is the same as this image: (Only a small part thereof of coarse!)

I have tried to realign/resize the map as an image-overlay on Google Earth, but then had no idea of how to output it or get the needed (and corrected) data from it.

Do you know how to use these, convert them to tiles or tips/tutorials that could help me fix this and get the maps straight?

If possible I would prefer to do it in MapTiler or at least on a Windows OS machine.

Answer 1

I would follow up with the people you bought them from, and confirm what coordinate system/projection they are in. They may not be WSG84 at all. It's likely if they are older that they are a NAD27 or other datum that will need to be reprojected.

Answer 2

The maps were probably hand drawn, then later scanned and may not exactly match the intended projection system. You best bet is probably to georectify the images against known locations and use those georectified images in your application.