[MapServer-users] Wrong and inconsistent GetFeatureInfo result for CLUSTER layer

[Seth G]

Hi Erik,

Are you able to confirm the issue still exists on newer versions of MapServer (8.4 or 8.2.2)?
There was a fix related to CLUSTER and PostGIS added to the newer versions, see https://github.com/MapServer/MapServer/pull/7111.

Seth

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On Tue, Feb 18, 2025, at 10:16 AM, Guldberg, Erik via MapServer-users wrote:
> It's interesting to note that, if I set a label, like the name of the object ("tittel"), it's always correct. It's only the getFeatureInfo that is wrong.
>  
> Also, I've tried to create a cluster layer from another dataset, where the main different is, I believe, that the projection is different, and I don't have the same problem there. Using the same cluster settings.
>  
> *Fra:* MapServer-users <mapserver-users-bounces at lists.osgeo.org> *På vegne av *Guldberg, Erik via MapServer-users
> *Sendt:* fredag 14. februar 2025 14:51
> *Til:* mapserver-users at lists.osgeo.org
> *Emne:* [MapServer-users] Wrong and inconsistent GetFeatureInfo result for CLUSTER layer
>  
> Hi,
> I have a WMS service, https://kart.ra.no/wms/brukerminner, where I have problems getting correct getFeatureInfo results from a layer with CLUSTER content.
>  
> It contains the cluster layer and a regular point layer for the same data. The regular point layer is shown at 1:50 000.
>  
> For single objects in both the cluster layer, I want to be able to use getFeatureInfo. This works, but the problem is that the results most of the time are wrong, and that they change for time to time, likely due to change in zoom level. For the regular point layer, the result is always correct. I've also created a test cluster layer without the scale limit, and that also gives the correct result if I zoom in enough.
>  
> All the symbols are placed correctly in the map, for all layers. I've used the database, and also this OGC API service (that uses the same data source as the WMS) as a reference: https://api.ra.no/brukerminner
>  
> I'm using MapServer version 7.6.4.
>  
> Some example queries, using QGIS.
> Wrong result. The object I get in the getfeatureinfo is 64 km away from where I clicked.
> https://kart.ra.no/wms/brukerminner?language=nor&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetFeatureInfo&BBOX=760392.02671199827454984%2C8263040.88853696268051863%2C1033357.36004533339291811%2C8407916.1385369636118412&CRS=EPSG%3A3857&WIDTH=1984&HEIGHT=1053&LAYERS=Brukerminner&STYLES=&FORMAT=image%2Fpng&QUERY_LAYERS=Brukerminner&INFO_FORMAT=text%2Fhtml&I=1069&J=616&FEATURE_COUNT=10
>  
> Zoomed in a bit more gives another, wrong result. This is 8.7 km away from where I clicked:
> https://kart.ra.no/wms/brukerminner?language=nor&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetFeatureInfo&BBOX=871972.11004533257801086%2C8307721.07603696547448635%2C940213.44337866583373398%2C8343939.88853696547448635&CRS=EPSG%3A3857&WIDTH=1984&HEIGHT=1053&LAYERS=Brukerminner&STYLES=&FORMAT=image%2Fpng&QUERY_LAYERS=Brukerminner&INFO_FORMAT=text%2Fhtml&I=1022&J=627&FEATURE_COUNT=10
>  
> This is the Test-layer, how it looks now. I've tried different variations of PROCESSING settings.
>  
> LAYER
>                 NAME "TEST"
>                 DEBUG 5
>                 TYPE POINT
>                 STATUS ON
>                 TEMPLATE "../templates/brukerminner.html"
>                 HEADER "../templates/header.html"
>                 FOOTER "../templates/footer.html"
>     TOLERANCEUNITS pixels
>                 TOLERANCE 25
>     # MINSCALEDENOM 50000
>                 METADATA
>                                "wms_enable_request" "*"
>         "wms_include_items" "tittel"
>  
>         "wms_title" "TEST"
>                                "wms_feature_info_mime_type" "text/html"
>  
> END                     
> PROJECTION
>                 "init=epsg:4326"
> END
>  
> EXTENT -19.76 54.57 45.57 82.67  #4326
> PROCESSING "CLOSE_CONNECTION=DEFER"
>  
> CONNECTIONTYPE POSTGIS
> CONNECTION "host=host  dbname=db user=user password=password port=5432"
> DATA "geom from xx.xx using unique id using srid=4326"
>  
>  
> LABELITEM "Cluster_FeatureCount"
>  
> # PROCESSING "CLUSTER_ALGORITHM=SIMPLE"
> PROCESSING "CLUSTER_GET_ALL_SHAPES=ON"
> PROCESSING "ITEMS=tittel,beskrivelse,fylke,kommune,opprettet,endret,opprettet_av,linkkulturminnesok,gpsposisjon"
> # PROCESSING "CLUSTER_KEEP_LOCATIONS=ON"
> CLUSTER
> MAXDISTANCE 50
>  
> REGION "ellipse"
> END
>  
> CLASS
>                 NAME "Brukerminne"
>     EXPRESSION ("[Cluster_FeatureCount]" = "1")
>                 STYLE
>                                SYMBOL "brukerminne"
>         COLOR 200 0 0
>                                SIZE 27
>         OFFSET 0 -13.5
>                 END
> END
> END              
>  
>  
> Anyone with ideas on what's wrong?
>  
>  
> Thanks,
> Erik
>  
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