using a png image with the mapping functions

Currently we show a map using the coast and topo data sets along with the geoshow function and then plot various data on top of it. I'd like to use a satellite image (e.g. http://eoimages.gsfc.nasa.gov/images/imagerecords/74000/74518/world.topo.200412.3x5400x2700.png) and then plot a lat/lon grid on top of it and then use the geoshow and plotm functions with it. How would this best be done? I've tried the geoshow(image, R) but I don't get my pretty picture:

a = imread('world.topo.200412.3x5400x2700.png');
spacing = 180/2700;
geoshow(a, [spacing, 90, -180]);

Thanks for any help.

[Xel Ch]

Hello, I am looking to accomplish something very similar, and was wondering if you ever received an answer to your problem? Thanks!

[Chad Greene]

The first question is figuring out what map projection was used to create the png image, because you'll need to use the same projection when plotting coast lines.

[jonas]

I believe there's a fileexchange function somewhere that let's you navigate through gps images. Will see if I can find.

EDIT: this one I believe ( link ). And here's another one ( link )