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| GeoCommunity Mailing List |
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| Subject: | Re: [gislist] SRTM |
| Date: |
08/09/2006 02:35:00 AM |
| From: |
Vassil Vassilev |
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Hugo,
yes SRTM could be used for the orthorectification of the satellite images -=
even for VHR like Ikonos and Quickbird - of course it depends what accurac=
y you want to achive, but using SRTM for such images is preferrable if you =
have plain terrain - not mountainous.
If fact you don't need to cut the SRTM in order to use it for orhtorectific=
ation. What is substantial is that the area of your image must fall inside =
the SRTM file. If not you have to mosaic the tiles of the SRTM.
But if you want to cut the file it depends what software you are using - on=
ly ArcInfo or image processing software - all of them have features which y=
ou could use to cut the file - but what I could propose you is not to cut i=
t - there is no sense of doing this.
Of course in some softwares there is a some sort of bug (at least I encoute=
red this in ERDAS and PCI Geomatics) if your DEM is much larger than the ar=
ea of the output ortho image, the software will try to create larger file w=
ith NO DATA values, but you could overcome this with specifying the ULX, UL=
Y, LRX and LRY of the output image.
Something important do not reproject the SRTM, because you will loose some =
accuracy of the Z-values.
Hope it helps,
Vassil Vassilev
Remote Sensing Application Center - ReSAC
Bulgaria
www.resac-bg.org
Hugo Roesch <airphoto2003@yahoo.com> wrote: A SRTM file could be used as a =
DEM for creating an orthophoto, if yes, how to cut it to ajust on the geoti=
ff photo in order to proceed ?
=
Thanks =
Hugo Roesch
airphoto2003@yahoo.com
=
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