[mapserver-users] WCS GetCoverage request one by one pixel

[Bakker, Anton]

Hi all,

I am running into a problem when sending HTTP requests to a MapServer backed WCS service.  I am trying to request a GeoTIFF of exactly 1 by 1 pixel, however this request fails by responding with a huge pixel (here is the describeCoverage request of the coverage requested):

https://geodata.nationaalgeoregister.nl/ahn3/wcs?service=WCS&Request=GetCoverage&version=2.0.1&CoverageId=ahn3_05m_dsm&format=image/tiff&subset=x(196396.75,196397.25)&subset=y(450031.75,450032.25)

When I modify the request to cover an area of 2X2 pixels, the response turns out fine:

https://geodata.nationaalgeoregister.nl/ahn3/wcs?service=WCS&Request=GetCoverage&version=2.0.1&CoverageId=ahn3_05m_dsm&format=image/tiff&subset=x(196396.75,196397.75)&subset=y(450031.75,450032.75)

See the screenshots hosted on imgur; (https://imgur.com/a/8IBGs3G (first screenshot is the erronous response of the request with the 1X1 extent, second screenshot is the result of the 2X2 request).

The MapServer version we are running is 7.4.3. Here is an excerpt of the mapfile that is used to configure the WCS service:

LAYER
    NAME ahn3_05m_dsm
    METADATA
      "wcs_srs"              "EPSG:28992"
      "wcs_label"           "ahn3_05m_dsm"
      "wcs_rangeset_name"   "ahn3_05m_dsm"
      "wcs_rangeset_label"  "ahn3_05m_dsm"
      "wcs_extent"          "10000 250000 356250 618750"
      "wcs_resolution"      "0.5 0.5"
      "wcs_formats"         "GEOTIFF_FLOAT32 GEOTIFF_BYTE GEOTIFF_INT16 GEOTIFF_RGB"
      "wcs_imagemode"       "FLOAT32"
      "wcs_bandcount"       "1"
    END
    TYPE RASTER
    DUMP TRUE
    STATUS ON
    DATA /srv/data/ahn3_05m_dsm/ahn3_05m_dsm.vrt
    PROCESSING "RESAMPLE=BILINEAR"
    PROJECTION
      "init=epsg:28992"
    END
END

I quickly skimmed the issue tracker on Github but could not find any issue causing this problem. Any thoughts on the cause of the problem are highly appreciated.

Kind regards,

Anton Bakker, Software Engineer
Kadaster / Geo- en Vastgoedinformatie en Advies / PDOK
tel. 06 - 29 737 351
anton.bakker at kadaster.nl
www.kadaster.nl<http://www.kadaster.nl>



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