[gdal-dev] Building a Mercator Image from Un-projected
data..Majorconfusion and help requested.
Christopher Barker
Chris.Barker at noaa.gov
Tue Nov 3 19:07:07 EST 2009
Cassanova, Bill wrote:
> Thank you for your response.
> Your email motivated me to try something. Not sure it's quite right but
> it does seem closer:
It looks right at a quick glance, but note that you are essentially
re-writing gdalwarp -- is that code too opaque to make use of?
> I ran the gdalwarp process on an unprojected image and as far as I can
> tell the image produced by this code and the image produced from that
> code are exactly the same.
right -- by default, gdalwarp uses nearest neighbor interpolation, which
is pretty much what you've done. You might try one of the other
interpolation methods, and see if the results look nicer:
$ gdalwarp
Usage: gdalwarp [--help-general] [--formats]
[-s_srs srs_def] [-t_srs srs_def] [-to "NAME=VALUE"]
[-order n] [-tps] [-rpc] [-geoloc] [-et err_threshold]
[-te xmin ymin xmax ymax] [-tr xres yres] [-ts width height]
[-wo "NAME=VALUE"] [-ot Byte/Int16/...] [-wt Byte/Int16]
[-srcnodata "value [value...]"] [-dstnodata "value [value...]"]
-dstalpha
[-r resampling_method] [-wm memory_in_mb] [-multi] [-q]
[-cutline datasource] [-cl layer] [-cwhere expression]
[-csql statement] [-cblend dist_in_pixels]
[-of format] [-co "NAME=VALUE"]*
srcfile* dstfile
Available resampling methods:
near (default), bilinear, cubic, cubicspline, lanczos.
so you should be abel to do (untested):
gdalwarp -s_srs '+proj=merc' -r cubic
hiradff_200910121800_f180_weather_wx.tiff
warped.tiff
It depends some on your image, but it could look quite a bit nicer.
-Chris
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker at noaa.gov
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