[Freegis-list] Newbie Question

[Nico de Haen]

Hi Frank,

Thanks for your infos. I want to implement a tool for websites, using 
the google map API for planing bycicle tours and storing them. I can 
calculate the distance of points, but it would of course be nice, also 
to include the elevation (especially for biker ;-)

What I don't understand: Where does your server get the data from? Do 
you store it on your server? That must be a pretty big amount of data, 
if it includes the elevation of all points of the world in a grid of 
let's say 100 meters.

Google Earth displays the elevation for each point of the world, but 
they don't offer an API to query such data via a web service or 
something similar.

These WCS servers cannot be queried for single points?

I'm sorry for my lousy knowledge concerning geo data, but I'm a web 
programmer and haven't done anything like that before...

best regards,

Nico

--- Original Nachricht ---
Absender: Frank Warmerdam
Datum: 16.02.2006 21:11
> Nico de Haen wrote:
>> This calculator gives only the geoid height, not the height of the 
>> surface above sea level.
>> (For Mount Helen,  46°11'49.01"N, 122°10'35.45"W it shows 4.15 m...)
> 
> Nico,
> 
> There are WCS servers providing elevation data for the world that you could
> query.  I run an SRTM30 server, but that is pretty coarse data.  What
> degree of spatial precision were you needing?
> 
>    http://maps.gdal.org/
> 
> WCS can be queried from from PHP, but the return result (at least of my
> server) is a raster file which might be hard for you to extract the value
> from.  In theory I could enable "WMS getfeatureinfo" style query from the
> raster data on the corrsponding WMS service and then you would get a small
> GML document.  But I'm not sure how hard that would be to get working.
> 
> Best regards,