[GRASSLIST:1683] Re: ASTER

[Markus Neteler]

On Tue, Nov 04, 2003 at 05:40:07PM +0100, Ivan Marchesini wrote:
> Hy to all
> 
> can someone say me where I can find some information about how to use RELATIVE 
> ASTER DEM???
> I have downloaded some of these granules, but using the area of 
> superimposition between them I discovered that the z elevation is quite 
> different between each other....

Right, there are also absolute DEMs, but the user has to provide GCPs.
 
> I tried to see documentation but it is not really clear....

See some links here:
http://mpa.itc.it/rs/asterdem/index.html
 
> have I to use GCPs???

yes. You have to deliver GCPs:
http://lpdaac2.usgs.gov/custhelp/product_info.asp?p_refno=020207-000004

> or similar??

It's not a trivial task as you have to find the corresponding 3N and 3B
images and to deliver the GCPs related to the scanlines in these
images (I may be wrong, but cannot find the document right now stating this).

Just dig around the "asterweb" site.

Markus

-- 
Markus Neteler     <neteler at itc.it>       http://mpa.itc.it
ITC-irst, Istituto per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
Via Sommarive, 18        -       38050 Povo (Trento), Italy