[GRASS-user] Fwd: GMorph> ASTER GDEM is out

Carlos "Guâno" Grohmann carlos.grohmann at gmail.com
Mon Jun 29 18:14:53 EDT 2009

---------- Forwarded message ----------
From: Hannes Reuter <gisxperts at web.de>
Date: Mon, Jun 29, 2009 at 13:01
Subject: GMorph> ASTER GDEM is out
To: geomorphometry at yahoogroups.com

Dear geomorphometry people,

some really really good news today:
NASA/METI released today the 30m global (83degreesNS, ~22600 scenes)
ASTER GDEM based on 1,264,118 single ASTER dems from 1.4 million scenes
in total. 95% vertical ci: 20 meters, 95% horizontal ci: 30 meters)
see http://www.gdem.aster.ersdac.or.jp/

congratulations to NASA/METI to provide the worldwide community with
such a long awaited dataset. just a short additional note:

>> from website
Initial studies to validate and characterize the ASTER GDEM confirm that
pre-production accuracy estimates are generally achieved for most of the
global land surface, although results do vary and true accuracies do not
meet pre-production estimates for some areas. In addition, Version 1 of
the ASTER GDEM does contain certain residual anomalies and artifacts
that affect the accuracy of the product and may be impediments to
effective utilization for certain applications. Consequently, METI and
NASA acknowledge that Version 1 of the ASTER GDEM should be viewed as
“experimental” or “research grade.” Nevertheless, they are confident
that the ASTER GDEM represents an important contribution to the global
earth observation community.

the link to the evaluation report will be probably be published
today/the coming days. as i/we had the possibility to evaluate 5 tiles
beforehand - from our analysis i/we can tell that you will run into some
of the following:
step anomalies across mosaicing edges,
mole runs,
sinks (we observed some down to 180m below the surrounding),
artifical mountains (up to 200m)
non existing water mask
in case only a couple of images n<4 have been used also the horizontal
accuracy has some interesting features sometimes...

which certanly might or might not influence the calculation of your
terrain parameters. i know you all can derive your own conclusions.

all depends on your tile ... ;-)

data can be downloaded from JAPAN/METI at
or LP DAAC -> https://wist.echo.nasa.gov/~wist/api/imswelcome/.
restrictions of 100 tiles apply and only 16 connections at the same time
are allowed.....so you might have to wait a bit.

cheers hannes...

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Carlos Henrique Grohmann - Geologist D.Sc.
a.k.a. Guano - Linux User #89721
ResearcherID: A-9030-2008


Can’t stop the signal.

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