[gdal-dev] Reprojecting rasters

[christian.mueller at nvoe.at]

I am not sure here, but this looks like  each tile is projected for itself.

My procedure always is

1) Build a large image without tiles
2) Reproject
3) Create Tiles/pyramids

Try to avoid TILED=YES and reproject  within the same gdalwarp call.


Quoting Rob <gis at vanbooth.com>:

> Hi
>
> [Apols for the X-post]
>
> I'm trying to reproject a set of rasters in order to improve performance on
> my application.
>
> I have a set of rasters in OSGB (EPSG:27700) that I want to pre-process so
> that they are in WGS84 (EPSG:4326) within GeoServer, rather than relying on
> GeoServer to do the reprojection on the fly.
>
> I have been reprojecting the rasters using the following command
>
>
> gdalwarp -of GTiff -s_srs "EPSG:27700" -t_srs "EPSG:4326" -co "TILED=YES"
> -co "COMPRESS=LZW" -co "TFW=YES" OLDNAME.TIF NEWNAME.TIF
>
>
> I have used the ImageMosaic datastore to load these into GeoServer and can
> view them.  So far, so good.
>
> However, there seems to be large gaps between the 'tiles' so that roads no
> longer join up and forests have big white gaps within them.
>
>> From checking the rasters and the resultant world files, I've noticed a few
> things.
>
> 1) The image sizes are not constant.  All of my original tiles are the same
> size.  It has raised an interesting question of whether the meridian line
> runs parallel to an OSGB Y-axis.
> 2) The worldfiles also contain some curious values.  I understand that the
> 1st and 4th parameters in a worldfile are the real world distance of a
> single pixel, but they seem to have the same value in despite the fact that
> the image size changes from being square to being rectangular.
>
> Whether those things mean anything, or are perfectly legitimate when
> reprojecting, I don't know, I just thought I should mention them.
>
> Has anybody got any advice on how to reproject a full set of rasters, or
> what I have done wrong?
>
> Thanks
>
> Rob
>



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