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I use a model from the Netherlands Hydrografic Office (Dienst der Hydrografie) to see what the difference is between Lowest Astronomical Tide (LAT) and Mean Sea Level (MSL). It's a WMS: https://inspire.caris.nl/server/services/ows/view/map/amplitude-getij_IVS

I would like to make a vectorfile with 50mx50m polygons for my administration area with the value (difference LAT-MSL) stated per polygon, based on the 384mx640m grid of the WMS. The reason for this is, so I can use it as a reference for other vectorfiles.

Here's the snag: If I try to save to WMS as a raster it loses the data. If i try to use the WMS as a raster for a "Raster Values to Points" or similar, i get an error:

The following layers were not correctly generated.<ul><li>/tmp/processing_07c3ae2f9d234b11bc16e7e072416172/0c6df7c5f0434ecab9f10c07759f7495/SHAPES.shp</li></ul>You can check the 'Log Messages Panel' in QGIS main window to find more information about the execution of the algorithm.

In the log messages panel it says:

2019-12-20T14:47:21     INFO    SAGA execution commands
             io_gdal 0 -TRANSFORM 1 -RESAMPLING 3 -GRIDS "/tmp/processing_07c3ae2f9d234b11bc16e7e072416172/3e3aed3cfdb640fe9cfece2b6d8fbc8c/OFGridObservation.sgrd" -FILES "contextualWMSLegend=1&crs=EPSG:4326&dpiMode=7&featureCount=10&format=image/png&layers=LAT_VIEW.OF.GridObservation&styles&url=https://inspire.caris.nl/server/services/ows/view/map/amplitude-getij_IVS"
             shapes_grid "Grid Values to Points" -GRIDS "/tmp/processing_07c3ae2f9d234b11bc16e7e072416172/3e3aed3cfdb640fe9cfece2b6d8fbc8c/OFGridObservation.sgrd" -NODATA true -TYPE 0 -SHAPES "/tmp/processing_07c3ae2f9d234b11bc16e7e072416172/a834381b9b3e4e0195ca7a987d68f3eb/SHAPES.shp"
2019-12-20T14:47:24     INFO    SAGA execution console output
             ERROR 4: contextualWMSLegend=1&crs=EPSG:4326&dpiMode=7&featureCount=10&format=image/png&layers=LAT_VIEW.OF.GridObservation&styles&url=https://inspire.caris.nl/server/services/ows/view/map/amplitude-getij_IVS: No such file or directory
             ____________________________

             ##### ## ##### ##
             ### ### ## ###
             ### # ## ## #### # ##
             ### ##### ## # #####
             ##### # ## ##### # ##
             ____________________________

             SAGA Version: 2.3.1

             ____________________________
             library path: /usr/lib/x86_64-linux-gnu/saga/
             library name: libio_gdal
             library : GDAL/OGR
             tool : Import Raster
             author : O.Conrad (c) 2007 (A.Ringeler)
             processors : 4 [4]
             ____________________________



             Parameters


             Grids: No objects
             Files: "contextualWMSLegend=1&crs=EPSG:4326&dpiMode=7&featureCount=10&format=image/png&layers=LAT_VIEW.OF.GridObservation&styles&url=https://inspire.caris.nl/server/services/ows/view/map/amplitude-getij_IVS"
             Select from Multiple Bands:
             Alphanumeric Sorting: yes
             Transformation: yes
             Resampling: B-Spline Interpolation


             loading: contextualWMSLegend=1&crs=EPSG:4326&dpiMode=7&featureCount=10&format=image/png&layers=LAT_VIEW.OF.GridObservation&styles&url=https://inspire.caris.nl/server/services/ows/view/map/amplitude-getij_IVS
             failed: could not find a suitable import driver
             Error: executing tool [Grid Values to Points]
             ____________________________

             ##### ## ##### ##
             ### ### ## ###
             ### # ## ## #### # ##
             ### ##### ## # #####
             ##### # ## ##### # ##
             ____________________________

             SAGA Version: 2.3.1

             ____________________________
             library path: /usr/lib/x86_64-linux-gnu/saga/
             library name: libshapes_grid
             library : Grid Tools
             tool : Grid Values to Points
             author : O.Conrad (c) 2001
             processors : 4 [4]
             ____________________________

             Load grid: /tmp/processing_07c3ae2f9d234b11bc16e7e072416172/3e3aed3cfdb640fe9cfece2b6d8fbc8c/OFGridObservation.sgrd...
             failed
             Grid Values to Points: could not initialize data objects

I know I am screwin this up because of a lack of knowledge. I am new to the raster-side of GIS. What steps do I need to undertake to at least get from the WMS to a vector grid with the value LAT-MSL?

  • 2
    WMS are just image they don't really contain informations that's why you seem to loose the data when saving it, what you need is a WCS service for it to work. You may try look on the Netherlands Hydrografic Office website if they offer this data for download – J.R Dec 20 '19 at 15:51
  • 1
    I'm not completely familiar with WMS format, but I believe you can sometimes save a portion of a WMS as a raster. Here's a link with more info: gis.stackexchange.com/questions/190927/… Whether it actually contains the information you need depends on the image. – csk Dec 20 '19 at 18:53
  • O, thnx I will give it a go, the thing is that when I use the information tool om a wms point it gives me 3 values: x y and the difference between LAT and MSL – CaptainAhab Dec 20 '19 at 19:10

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