Greetings
I have an image without any GCP’s but, teorethically it’s in WGS84. I have all pixel positions outside that file. My question is, what should I do in GRASS to rectify/project this image? I thought in two solutions
1- import, using r.in.gdal in a XY projection and rectify. Is it possible to rectify a raster, with i.rectify, using a file outside GRASS (e.g. a text file?)
2- use GDAL to add GCP’s points to file and then import to grass already rectified…
GreetingsI have an image without any
GCP's but, teorethically it's in WGS84. I have all
pixel positions outside that file. My question is, what
should I do in GRASS to rectify/project this image? I
thought in two solutions
1- import, using r.in.gdal in a XY projection and
rectify. Is it possible to rectify a raster, with i.rectify,
using a file outside GRASS (e.g. a text file?)2-
use GDAL to add GCP's points to file and then import to
grass already rectified..
I would use gdal_translate to add GCPs to the file and then
use gdalwarp to reproject it to what you want.
the other way is to create a group/$GROUPNAME/POINTS file by
hand. it is a very simple format, use one of the grass geo-ref
tools to create a couple of sample GCPs by hand and then edit
the file to place your known values in the right way. There
are column headings in the POINTS file.
be careful that gdal considers 1,1 to be the top left, while
grass considers 1,1 the bottom left pixel. so you might have to
apply rows-y at some point if swapping between the two.
(? or 0,0, so +/- 1 pixel ?)
Greetings I have an image without any GCP's but, teorethically it's
in WGS84. I have all pixel positions outside that file. My question
is, what should I do in GRASS to rectify/project this image? I
thought in two solutions
If the image doesn't require warping, but is just missing a
georereference, use r.region to put in place.
How can r.region put my image in place? Because it’s a geostationary data so the image corners don’t have the same coordinates (e.g. Top Left and Top Right don’t have the same latitude). But I do have some GCP’s for the image. So r.region doesn’t help me (as far as I can see).
Nikos
Greetings I have an image without any GCP’s but, teorethically it’s
in WGS84. I have all pixel positions outside that file. My question
is, what should I do in GRASS to rectify/project this image? I
thought in two solutions
If the image doesn’t require warping, but is just missing a
georereference, use r.region to put in place.
Nikos,
as Maciek said, your image seems to need warping, so I fear you have no
other solution than georectify it.
Vincent
Le lundi 22 février 2010 à 11:03 +0000, Nikos Dumakis a écrit :
How can r.region put my image in place? Because it's a geostationary
data so the image corners don't have the same coordinates (e.g. Top
Left and Top Right don't have the same latitude). But I do have some
GCP's for the image. So r.region doesn't help me (as far as I can
see).
Nikos
On Sun, Feb 21, 2010 at 1:35 PM, Maciej Sieczka <msieczka@sieczka.org>
wrote:
Nikos Dumakis pisze:
Greetings I have an image without any GCP's but,
teorethically it's
in WGS84. I have all pixel positions outside that
file. My question
is, what should I do in GRASS to rectify/project this
image? I
thought in two solutions
If the image doesn't require warping, but is just missing a
georereference, use r.region to put in place.