[gdal-dev] Meaning of some switches in the gdal utilities

[Theuns Heydenrych]

HI.

I am new to the libraries, and would like some more info on some of the
switches of the utilities.

I am mainly using the command line utilities.

On the gdaltransform utility:
1. -rpc: Force use of RPCs.
a) What does this mean exactly? I can see, the utility is forced to use
rps's.
b) What is a rpc, sorry for this stupid question, but please, what does
it stands for?
c) How do i provide these rpc's?

2. -geoloc: Force use of Geolocation Arrays.
a) Again i can gather the utility is forced to use geolocation arrays,
how to a supply these?
b) What is the format for these arrays, comma delimited, space
delimited, should it be in a file...?

3. -gcp pixel line easting northing [elevation]:
a) Ok, i could figure this one out, but what does "gcp" stands for, "geo
control point"?

On the gdalwarp utility:
I have only used it once and would realy like to use it to more.
1) -cutline datasource:
a) What will this do for me exactly, will it crop the image for me
according to a extend in a shapefile?
b) Could this be a polygon in a shapefile?


I have only used the utilities now for a few days, and are really
impressed, i could do all my geolocation work with out opening any
proprietary software(being ArcMap).

I would like to play more with the utilities, like to merge some of the
raster data, and cut it up in tiles and do some warping on some of the
georeferenced raster i down loaded from the net.

About some of the questions above, may seem very stupid, but hey, i have
to know some of it, to use the utilities to its full potential.

Thanks in advance, and best regards.
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