[mapserver-users] GTOPO30, Raster Maps, and Projections

[Armin Burger]

Frederik,

you could try it with a world file 'yourimage.pgw' and the values
0.015625
0.000000
0.000000
-0.015748
-10.00000
70.00000

Armin

> Hi,

>    I'm using MapServer 4.3 (but will upgrade to 4.4/4.5 if required to
> solve my problem).

> I have a PNG map of Europe, generated from GTOPO30 elevation data. I
> created it using the free "drawmap" utility; the file is 1920x2540
> pixels in size and depicts the area from (30N,10W) to (70N,20E).

> As far as I understand, drawmap doesn't really use a proper
> projection, it just stretches the grid to match whatever coordinates
> and pixel sizes I specify.

> How can I use this PNG bitmap as a raster background for my MapServer
> maps? I have read the relevant documentation and got "something"
> to show up but I am at a loss how to create a proper world file for
> the data I have. The docs say:

> "The world file contents look like the following. The first
> coefficient is the X pixel size. The second and third are rotational
> coefficients (and should normally be NULL). The fourth is the Y pixel
> size, normally negative indicating that Y decreases as you move down
> from the top left origin. The final two values are the X and Y
> location of the center of the top left pixel."

> This seems to imply that I need a bitmap in which the pixel size (in
> meters) is constant - something which cannot be said of my map!

> If this is too difficult, then is there some other way to use GTOPO30
> data with MapServer (besides creating raster files with drawmap and
> taking it from there)?

> Thanks,
> Frederik

> --
> Frederik Ramm  ##  eMail frederik at remote.org  ##  N48°59.94 E008°24.36'