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Actually, I'm working on the implementation of WCS 2.0 service with the latest version of Mapserver (7.0.7). On GetCapabilities request, the XML response show us a list of layers (wcs:CoverageId) with a CoverageSubtype for the layer in wcs:Contents, which are available and supported by the server

The first one is, What is the difference between GridCoverage, RectifiedGridCoverage, MultiPointCoverage, MultiCurveCoverage, MultiSurfaceCoverage, MultiSolidCoverage, etc ?

Someone can illustrate it with schemas

The second one is, How Mapserver defines wcs:CoverageSubtype value in XML response from GeoTIFF file ? In mapfile (*.map), there are no information about grids.

Mapfile example

MAP
    NAME wcs_server
    SIZE 1140 550
    EXTENT -90 -180 90 180
    IMAGECOLOR 255 255 255

    WEB
        IMAGEPATH "/home/tmp/"
        IMAGEURL "/tmp/"
        METADATA
            "wcs_label"                             "Test Mapserver 7"
            "wcs_description"                       "En cours de test"
            "wcs_onlineresource"                    "http//172.17.0.2:9999/cgi-bin/mapserv?"
            "wcs_fees"                              "none"
            "wcs_accessconstraints"                 "none"
            "wcs_keywordlist"                       "wcs test"
            "wcs_address"                           "Rue Truc muche"
            "wcs_city"                              "BLAGNAC"
            "wcs_postcode"                          "31700"
            "wcs_country"                           "FRANCE"
            "wcs_contactelectronicmailaddress"      "test@bla"
            "wcs_contactperson"                     "Quentin SALLES"
            "wcs_contactorganization"               "AKKA-ARTAL"
            "wcs_contactposition"                   "ingenieur"
            "wcs_contactvoicetelephone"             "+33 1 23 45 67 89"
            "wcs_enable_request"                    "*"
            "wms_enable_request"                    "*"
            "wms_title"                             "Test Mapserver 7"
            "wms_srs"                               "EPSG:4326"
            "wms_onlineresource"                    "http://172.17.0.3:9999/cgi-bin/mapserv?"
        END
    END
    PROJECTION
        "init=epsg:4326"
    END

    LAYER
        NAME World
        METADATA
            "wcs_label"                             "Background/World"
            "wcs_rangeset_name"                     "Range 1"
            "wcs_rangeset_label"                    "My label"
        END
        COMPOSITE
                OPACITY 20
        END
        TYPE RASTER
        STATUS ON
        DATA "/home/synext/tmp/Digital_Chart_of_the_World.tiff"
        PROJECTION
            "init=epsg:4326"
        END
    END   
END

All layers contain "RectifiedGridCoverage" as value in wcs:CoverageSubtype. "For an raster layer I can see only "RectifiedGridCoverage" in GetCapabilities and I am not sure if anything else makes sense with MapServer" ---> Where I can found what you said ? In WCS OGC Documentation? I don't know if it's possible to have others values in wcs:CoverageSubtype ?

  • They come from this OGC standard portal.opengeospatial.org/files/?artifact_id=48553. – user30184 Feb 15 '18 at 14:39
  • I wonder how you have defined your layers. For an raster layer I can see only "RectifiedGridCoverage" in GetCapabilities and I am not sure if anything else makes sense with MapServer. Could you add relevant parts of your mapfile? – user30184 Feb 15 '18 at 15:06
  • I added a mapfile example on my message. – Quentin S33 Feb 15 '18 at 15:46
  • All layers contain "RectifiedGridCoverage" as value in wcs:CoverageSubtype. "For an raster layer I can see only "RectifiedGridCoverage" in GetCapabilities and I am not sure if anything else makes sense with MapServer" ---> Where I can found what you said ? In WCS OGC Documentation? I don't know if it's possible to have others values in wcs:CoverageSubtype – Quentin S33 Feb 15 '18 at 16:06
  • Don't forget that the Tour says that there should be only one question asked per question. To revise your question please use the edit button beneath it. – PolyGeo Feb 15 '18 at 22:30
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For WCS the main documentation to read are the OGC standards http://www.opengeospatial.org/standards/wcs. The types of coverages are defined in the GML standard https://portal.opengeospatial.org/files/?artifact_id=48553.

The WCS standard versions 1.0.0 and 1.1.x were explicitly limited to handle only grid coverages. This is from the WCS 1.1.2 standard

1 Scope This document specifies how a Web Coverage Service (WCS) describes and delivers multi-dimensional coverage data over the World Wide Web. This version of the Web Coverage Service is limited to describing and requesting grid (or "simple") coverages. Grid coverages have a domain comprised of regularly spaced locations along 0, 1, 2, or 3 axes of a spatial coordinate reference system. Their domain may also have a time dimension, which may be regularly or irregularly spaced. A coverage defines, at each location in the domain, a set of fields that may be scalar-valued (such as elevation), or vector-valued (such as brightness values in different parts of the electromagnetic spectrum). These fields (and their values) are known as the range of the coverage. The WCS interface, while limited in this version to regular grid coverages, is designed to extend in future versions to other coverage types defined in OGC Abstract Specification Topic 6, "The Coverage Type" [OGC 00-106].

In WCS version 2.0 it came possible to support also other coverage subtypes than grid types (gml:Grid or gml:RectifiedGrid) but it is by no means compulsory.

MapServer can deliver coverages only in some raster format and rasters are by nature grids. If grid is also georeferenced then it is of type gml:RectifiedGrid and that it what MapServer has in GetCapabilities. There is no need to define that in a mapfile. MapServer has also a constraint that rasters must be georeferenced (see http://www.mapserver.org/ogc/wcs_server.html LAYER PROJECTION must be set) and therefore the other possible alternative for rasters, non-rectified gml:Grid is not supported by MapServer.

The answer to question if is possible to have other coverage subtypes than "RectifiedGridCoverage" in the WCS GetCapabities with MapServer is No. MapServer can deliver only rectified grids and announcing anything else in GetCapabilities would be wrong.

  • Thanks for help ! I finally understand how grids are working. – Quentin S33 Mar 9 '18 at 14:12

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