[Mapserver-users] Raster Projection

[Gerry Creager]

To carry this a bit further, what happens when one uses a geotiff with 
appropriate registration on a projected map?  In general terms, (and 
it's early, I'm minus on sleep, and the coffee's not ready yet...) One 
has a non-projected raster image, rectifies it as well as possible with 
indices from ground reference, and registers it to the vector map, with 
some degree of rubbersheeting. OR, one can take the flat image, register 
and rectify, assuming a non-projected image, and then project it in a 
standard form.  The degree of distortion is similar.... correct?

Thus, what's easier and best practice?  The interest I have is that I'll 
be creating a set of GIF's (I need both animation and transparency) that 
I want to overlay atop a weather depiction map.  The GIFs will be 
unprojected but I can easily register the image to the various radar 
sites in the State, so rubbersheeting the image is a non-issue, if GDAL 
and the other adjunts will allow this.

TIA, gerry

Hubert Fröhlich wrote:
> 
> Frank Warmerdam wrote:
> 
> randy james wrote:
> 
> Hi List
> 
> I have some orthophotos in geotiff format. Some are in
> albers equal area and some are UTM, projection. H have
> been trying to reproject on the fly, but i cannot seem
> to  get it to work. The map projection is UTM so i do
> not have a problem with the orthos that are already in
> UTM, but cannot get the AEA orthos to load.
> 
> Been reading the list, and seen that raster layers are
> used as is and cannot be reprojected on the fly. Is
> this correct?
> 
> Is it possible to use shape tile index on the
> orthophotos, and reproject the shape file? I thought
> someone may have tried, if not i'll give it a try
> today.
> 
> 
> Randy,
> 
> MapServer configured with PROJ and GDAL support (and TIFF disabled)
> can reproject rasters on the fly; however, there are some limitations.
> 
>  o You can't generally mix images in different projections in an index
>    file.
>  o A given raster layer can only have one projections.
>  o If the file is handled through the non-GDAL TIFF driver reprojection
>    won't be supported.
>  o This stuff works in 3.6.x and 3.7dev and is likely working best in 
> the 3.7
>    version.
> 
> 
> 
> Frank,
> 
> what is (roughly) the difference between native TIFF/GeoTIFF support and 
> support by gdal? Seems that gdal is more capable? (you mentioned 
> reprojection)
> 
> What happens if I compile with native tiff support AND gdal support? 
> Does this make sense? (Or should I REALLY compile only with 
> --without-tiff  ? )
> 
> 
> Greetings,
> 
> Hubert
> 


-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University
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