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| Subject: | Re: [gislist] Steps to import GLCF data? |
| Date: |
03/01/2006 01:40:01 PM |
| From: |
Analisa Gunnell |
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Hello Larry,
I know what you're feeling, delving into RS land can be quite compelling
and yet, painful for the inexperienced. Anyway, having just had a
similar experience trying to track down True Color Imagery (which I am
still wearily working through at this time) here are the most relevant
things that I learned: a. Due to the enormous size of these data sets,
different sites have different means for tackling the issues of
compression. Many, such as the GLCF site, compress each band
individually (i.e. band 1 is red, band 2 is green, band 8 is
panchromatic and so forth). If you've downloaded a few tiffs (did you
do this for one scene, or one tiff for each scene of interest?) that are
showing as "Black and White" I would guess it's because you only have
one of the bands that you need. To make a True Color Composite you'll
need to do some processing to the data. Here is the most basic run down
of what these process steps are (or at least, what I did to make a
composite), and this assumes that you have GIS or RS software. First
you need to turn them into grids (cmd imagegrid), then you need to take
off the collars (cmd setnull values = 0), then you'll want to slice them
(them meaning every band of every scene you need... if you many scenes
as I did you'll want to automate this obviously), and finally you'll
want to mosaic EACH band of every scene (i.e. mosaic all the Band 1's,
Band 2's etc of different scenes) and then do a combine all of these
mosaiced bands into one large grid (cmd makestack). Yes, this is quite
a lot of effort on your part, and as I have learned, there are many
issues that still may arise even after you've done all of this
processing. One thing to be very aware of is that the dates of each
available scene may differ dramatically, which will really stand out in
your final product (i.e. one part of the image is was taken in june and
the other scene next to it was shot in January... there is a line of
snow that seems a tad bit odd). Depending on the size of your area you
may want to go with the Blue Marble products since they are already
processed and mosaiced (check out www. Geotorrent.org) . I'm currently
downloading a Blue marble image and so I haven't yet been able to see if
it will work for my needs, but at least it's a start. I hope this helps
a little. Feel free to email me if you need to! Just keep in mind that
I'm new at this too!
GOOD LUCK!!!
Analisa Noel Gunnell
Chief Cartographer/GIS Analyst
Ecotrust
721 NW Ninth Avenue, Suite 200
Portland, Oregon
97209
503.467.0750
analisa@ecotrust.org
www.ecotrust.org
www.inforain.org
www.tidepool.org
CONSERVATION ECONOMY
ECOLOGY-ECONOMY-EQUITY
Every animal knows more than you do.
- Nez Perce
-----Original Message-----
From: gislist-bounces@lists.geocomm.com
[mailto:gislist-bounces@lists.geocomm.com] On Behalf Of Larry F. Holt
Sent: Wednesday, March 01, 2006 10:13 AM
To: gislist@lists.geocomm.com
Subject: [gislist] Steps to import GLCF data?
Hey all-
I have been downloading several TIF's from the GLCF site
http://glcf.umiacs.umd.edu/index.shtml
They are Landsat ETM. What do I need to do to use them?
I thought what I was downloading was color, but all the TIF's appear BW.
Larry Holt
Director of Research
Birmingham Regional Chamber of Commerce
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