[Freegis-list] Lat/Long to Pixel Conversion for the Web

[Bernhard Reiter]

On Sat, Feb 14, 2004 at 04:44:46PM -0600, Mike Anderson wrote:
> I am new to GIS so bear with me. I have a ton of devices that I have the
> lat/long coordinates for. What I would like to do is find the corresponding
> bitmap pixel coordinates for these lat/longs in order to (1) plot my 
> devices on a scaled
> .gif and (2) generate a web imagemap behind a scaled .gif.
> 
> So, I've got the lat/longs, I've got a scaled image, I can find several
> points on the image where I know the lat/longs AND pixel values (if that
> makes any difference).

Usually you have to do 
	1) georeference your image,
	meaning that the software will know where each pixel is

	GRASS can do that, but it might be a bit overkill for the task.
	Maybe you can do a poor man solution involving step 2.
	Try so many projectiong, until it roughly fits for the
	purposes of drawing.

	2) project your lat/long coordinates in the map coordinates
	Your map coordinates are the pixel in this case.
	
	A lot of Free Software can do this.
	E.g. gmt

	If you did 1) then displaying the points should be easy.
	Check out igmt.

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