Hi Jukka, I finally managed to check up on your suggestion. I set the RESAMPLE mode to NEAREST in the mapfile on a MapServer instance running locally on my machine. This results in the same response as setting the resampling method in the url (see my previous email) :
http://localhost:32788/ahn3/wcs?service=WCS&Request=GetCoverage&version=2.0.1&CoverageId=ahn3_05m_dsm&format=image/tiff&subset=x(196396.75,196396.75)&subset=y(450031.75,450031.75) <?xml version="1.0" encoding="UTF-8"?> <ows:ExceptionReport xmlns:ows="http://www.opengis.net/ows/2.0"; xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; version="2.0.1" xml:lang="en-US" xsi:schemaLocation="http://www.opengis.net/ows/2.0 https://geodata.nationaalgeoregister.nl/ows/2.0/owsExceptionReport.xsd<http://www.opengis.net/ows/2.0%20https:/geodata.nationaalgeoregister.nl/ows/2.0/owsExceptionReport.xsd>"> <ows:Exception exceptionCode=""> <ows:ExceptionText>msImageCreate(): Image handling error. Attempt to allocate raw image failed, out of memory.</ows:ExceptionText> </ows:Exception> </ows:ExceptionReport> Also all resampling methods result in the same response (tested by supplying through the query parameter in the url). When I look in the logs I see that MapServer determines the dimensions of the request to be 0x0 pixels, causing the creation of the image to fail: 2020-05-06 17:38:11: (mod_fastcgi.c.421) FastCGI-stderr: Subset for X-axis found: x 2020-05-06 17:38:11: (mod_fastcgi.c.421) FastCGI-stderr: Subset for Y-axis found: y 2020-05-06 17:38:11: (mod_fastcgi.c.421) FastCGI-stderr: msWCSGetCoverage20(): Set parameters from originaldata. Width: 0, height: 0, cellsize: -nan, extent: -nan,-nan,-nan,-nan 2020-05-06 17:38:11: (mod_fastcgi.c.421) FastCGI-stderr: msImageCreate(): Image handling error. Attempt to allocate raw image failed, out of memory. I also quickly checked whether requesting a 1x1 subset works, but this fails by returning geotiff image of 1x1 pixel with a pixel size of "-135000,162500": http://localhost:32788/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) However requesting an image of 2x2 pixels still works as expected: http://localhost:32788/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) Kind regards, Anton ________________________________ From: Rahkonen Jukka (MML) <[email protected]<mailto:[email protected]>> Sent: Tuesday, April 7, 2020 5:49 PM To: Bakker, Anton <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> Subject: Re: WCS GetCoverage request one by one pixel Hi Anton, What I meant was to have a try by commenting out this line from your mapfile PROCESSING "RESAMPLE=BILINEAR" Actually it would be interesting to know what really happens if the interpolation/resampling method is configured in the mapfile and GetCoverage comes also with Interpolation parameter. -Jukka-
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