[GRASSLIST:7408] ERDAS Atcor vs. i.atcor

GRASS GRASS user
1

Hello,

I wonder if somebody can judge the goodness of performance for the output of
ERDAS Atcor (http://www.geosystems.de/atcor/) vs. GRASS i.atcor
(http://www.cs.sun.ac.za/~caz/6S/i.atcorr.html). Are their methods comparable
at all? I am not experienced in atmospheric correction and hence all the
algorithm are rather meaningless to me.

Any links, papers, comparisons etc. are welcome, thanks in advance, Martin

--
Martin Wegmann

DLR - German Aerospace Center
German Remote Sensing Data Center
@
Dept.of Geography
Remote Sensing and Biodiversity Unit
University of Wuerzburg
Am Hubland
97074 Würzburg

phone: +49-(0)931 - 888 4797
fax: +49-(0)931 - 888 4961
http://www.biota-africa.org
http://www.biogis.de

2

Hi Martin,

I can't tell you anything about the goodness or performance.

I just know that the moduls use different algorithms.
Atcor for ERDAS uses MODTRAN. The Grass module uses 6S.

As far as I know, MODTRAN is quite widely used.

The method to use for an atmospheric correction depends on
different factors:
on the kind of the atmospheric input data, the sensor, the spectral
bands you want to correct and of course on the purpose of your data
analyses.

An interesting document about the atmospheric correction of ASTER data
is provided by the NASA
http://eospso.gsfc.nasa.gov/eos_homepage/for_scientists/atbd/docs/ASTER/atbd-ast-09t.pdf.
I think this gives a good overview about the relevance of the different
parameters used for atmospheric corrections and their influence on the
accuracy of the results.

You could post this topic to the Applied GIS & RS mailing list
(http://www.matox.com/agisrs/).

If you'll find out something, I would quite interested in it :slight_smile:

Sorry that I can't tell you more. Hope this helps a bit!

Grit

Martin Wegmann wrote:

Hello,

I wonder if somebody can judge the goodness of performance for the output of ERDAS Atcor (http://www.geosystems.de/atcor/) vs. GRASS i.atcor (http://www.cs.sun.ac.za/~caz/6S/i.atcorr.html). Are their methods comparable at all? I am not experienced in atmospheric correction and hence all the algorithm are rather meaningless to me.

Any links, papers, comparisons etc. are welcome, thanks in advance, Martin

--
Grit Schuster, Environmental Scientist

Department of Physical Geography
Albert-Ludwigs Univeristy Freiburg
Werderring 4
D-79085 Freiburg

phone: +49-(0)761-2039124
fax: +49-(0)761-203-3596
email: grit.schuster@geographie.uni-freiburg.de
www: http://www.geographie.uni-freiburg.de/ipg/gkgl/gk.htm

3

Hi,

I need to import a Landsat image in FAST format. The CD contains the
following files

BAND1.DAT
BAND2.DAT
BAND3.DAT
BAND4.DAT
BAND5.DAT
BAND6.DAT
BAND7.DAT
FFORMAT.TXT
HEADER.DAT
README.TXT
TRAILER.DAT
TRAILER.TXT

How do I proceed to import this with r.in.gdal? So far, all I have
got is a recurrent " file xxx not recognized as a supported file
format"

Cheers

Armando Scalise
GeoInference
Patagonia Argentina
armando@geoinference.com
armandoh@gmail.com

4

Martin:

    I'd recommend also posting this question to the Remote Sensing listserv
I moderate at UC Davis: http://www.cstars.ucdavis.edu/starserv . We have a
lot of people use ATCOR and other image calibration programs on this
listserv! Please post your responses if and when you get them to this list,
I'm interested in hearing what you find out!

--j

On 7/1/05 5:02 AM, "Grit Schuster"
<grit.schuster@geographie.uni-freiburg.de> wrote:

Hi Martin,

I can't tell you anything about the goodness or performance.

I just know that the moduls use different algorithms.
Atcor for ERDAS uses MODTRAN. The Grass module uses 6S.

As far as I know, MODTRAN is quite widely used.

The method to use for an atmospheric correction depends on
different factors:
on the kind of the atmospheric input data, the sensor, the spectral
bands you want to correct and of course on the purpose of your data
analyses.

An interesting document about the atmospheric correction of ASTER data
is provided by the NASA
http://eospso.gsfc.nasa.gov/eos_homepage/for_scientists/atbd/docs/ASTER/atbd-a
st-09t.pdf.
I think this gives a good overview about the relevance of the different
parameters used for atmospheric corrections and their influence on the
accuracy of the results.

You could post this topic to the Applied GIS & RS mailing list
(http://www.matox.com/agisrs/).

If you'll find out something, I would quite interested in it :slight_smile:

Sorry that I can't tell you more. Hope this helps a bit!

Grit

Martin Wegmann wrote:

Hello,

I wonder if somebody can judge the goodness of performance for the output of
ERDAS Atcor (http://www.geosystems.de/atcor/) vs. GRASS i.atcor
(http://www.cs.sun.ac.za/~caz/6S/i.atcorr.html). Are their methods comparable
at all? I am not experienced in atmospheric correction and hence all the
algorithm are rather meaningless to me.

Any links, papers, comparisons etc. are welcome, thanks in advance, Martin

--
Jonathan A. Greenberg, PhD
NRC Research Associate
NASA Ames Research Center
MS 242-4
Moffett Field, CA 94035-1000
650-604-5896
AIM: jgrn307
MSN: jgrn307@hotmail.com

5

I need to import a Landsat image in FAST format. The CD contains the
following files

..

How do I proceed to import this with r.in.gdal? So far, all I have
got is a recurrent " file xxx not recognized as a supported file
format"

First try 'gdalinfo --formats' to check that FAST support is enabled.

supported gdal formats:
  http://www.gdal.org/formats_list.html

FAST is there:
  http://www.gdal.org/frmt_fast.html

so it should be possible to load it.

From that GDAL help page:

"Datasets in FAST format represented by several files: one or more
administrative headers and one or more files with actual image data in
raw format." ... "This driver wants administrative file for input."

so try 'r.in.gdal input=HEADER.DAT' (assuming that is the admin file)

If 'gdalinfo HEADER.DAT' doesn't work, you may have to try over on the
GDAL mailing list for more help.

Hamish

6

Hello,

Maciek referred me to Wolfgang Lück who did a comparison between MODTRAN and
6S. He will publish the results end of the year. However he received the
permission by Vermote to rewrite the Fortran code of 6S to C but not yet to
release it under the GPL.

please see this quote of his response for further informations:

"Thank you for your interest in i.atcor (6S). I am busy validating and
comparing results from this module with Atcor 2 & 3 as implemented in PCI. We
intend to improve it so that atmospheric products from MSG can be integrated
to define correction models more accurately. We also intend to improve the
HOT model for relative visibility extraction with a possible combination of
TC4 and HOT taking differences for land cover types (i.e water is problematic
with HOT) into account. I do not expect our implementations to be quite as
good as Richters models because we are no experts in atmospheric physics. I
hope to publish my thesis end of the year and will thereby then present a
quantitative comparison of the two models."
(wolfluck_AT_mweb.co.za)

regards, Martin

On Friday 01 July 2005 17:36, Jonathan Greenberg wrote:

Martin:

    I'd recommend also posting this question to the Remote Sensing listserv
I moderate at UC Davis: http://www.cstars.ucdavis.edu/starserv . We have a
lot of people use ATCOR and other image calibration programs on this
listserv! Please post your responses if and when you get them to this
list, I'm interested in hearing what you find out!

--j

On 7/1/05 5:02 AM, "Grit Schuster"

<grit.schuster@geographie.uni-freiburg.de> wrote:
> Hi Martin,
>
> I can't tell you anything about the goodness or performance.
>
> I just know that the moduls use different algorithms.
> Atcor for ERDAS uses MODTRAN. The Grass module uses 6S.
>
>
> As far as I know, MODTRAN is quite widely used.
>
> The method to use for an atmospheric correction depends on
> different factors:
> on the kind of the atmospheric input data, the sensor, the spectral
> bands you want to correct and of course on the purpose of your data
> analyses.
>
> An interesting document about the atmospheric correction of ASTER data
> is provided by the NASA
> http://eospso.gsfc.nasa.gov/eos_homepage/for_scientists/atbd/docs/ASTER/a
>tbd-a st-09t.pdf.
> I think this gives a good overview about the relevance of the different
> parameters used for atmospheric corrections and their influence on the
> accuracy of the results.
>
> You could post this topic to the Applied GIS & RS mailing list
> (http://www.matox.com/agisrs/).
>
> If you'll find out something, I would quite interested in it :slight_smile:
>
> Sorry that I can't tell you more. Hope this helps a bit!
>
> Grit
>
> Martin Wegmann wrote:
>> Hello,
>>
>> I wonder if somebody can judge the goodness of performance for the
>> output of ERDAS Atcor (http://www.geosystems.de/atcor/) vs. GRASS
>> i.atcor (http://www.cs.sun.ac.za/~caz/6S/i.atcorr.html). Are their
>> methods comparable at all? I am not experienced in atmospheric
>> correction and hence all the algorithm are rather meaningless to me.
>>
>> Any links, papers, comparisons etc. are welcome, thanks in advance,
>> Martin

--
Martin Wegmann

DLR - German Aerospace Center
German Remote Sensing Data Center
@
Dept.of Geography
Remote Sensing and Biodiversity Unit
University of Wuerzburg
Am Hubland
97074 Würzburg

phone: +49-(0)931 - 888 4797
fax: +49-(0)931 - 888 4961
http://www.biota-africa.org
http://www.biogis.de