[mapserver-users] Label attribute bindings

[Stephen Woodbridge]

Tim,

When you say "OS has determined the best position for the label", what 
form is this attribute in? Is the x-y position attribute columns? or 
some offset x-y attribute? or what?

If it is an x-y position that you would rather use that the default 
the_geom geometry position of the feature then it would probably be 
possible to create a view that makes that x-y appear as 
setsrid(makepoint(x_col,y_col),27700) as the_geom in the view and then 
add a record to the geometry_columns table for this view. for 
performance you might want to add this column to the orginal table and 
index it.

Then you should be able to renter the annotation using the view or the 
alternate column in the table.

-Steve W

Tim Urwin wrote:
> Hi all,
> 
> This is a questuion about label attribute bindings.
> 
> We are about to migrate some of our Ordnance Survey MasterMap data from 
> a propriety system to using mapserver serving the data from a PostGIS 
> database for screen maps. We are currently using Mapserver 5.02 and are 
> very happy with the results we have achieved so far, however, due to 
> only being able to set a single value for the position of a label has 
> caused much of the text to be badly misaligned with the underlying 
> features.
> 
> OS has determined the best position for the label and provide this as 
> attribute data for each text label point and we would like to be able to 
> utilise it. Is there anyway to make the position label attribute accept 
> a binding as some of the other values do, e.g. angle which we also use. 
> The problem we have is that no single value works with the data to 
> provide a good map result, therefore we would like to be able to use 
> each feature's value as opposed to a global value.
> 
> Any help or insights in how to achieve this will be gratefully received. 
> At the moment our applications access Mapserver via CGI mode directly 
> without the use of mapscript although we could investigate that option.
> 
> The following is an example of one of the entries in the mapfile for a 
> label layer.
> 
> LAYER
> 
>   NAME "Heritage labels"
> 
>   METADATA
>      "wms_title" "Heritage labels"
>      "wms_srs"   "EPSG:27700"
>      "wms_extent"   "0.0 0.0 700000.0 1300000.0"
>   END
> 
>   STATUS OFF
> 
>   CONNECTIONTYPE postgis
>   CONNECTION "user=XXXX password=XXXX dbname=XXXX host=XXXX port=XXXX"
>   DATA '"anchorpoint" from "cartographictext" using unique "fid" using 
> SRID=27700'
> 
>   PROCESSING    "CLOSE_CONNECTION=DEFER"
> 
>   TYPE Annotation
> 
>   LABELITEM 'textstring'
> 
>   FILTER ("layer" = '59')
> 
>   CLASS
>      NAME 'Antiquity Text (82)'
>         LABEL
>           COLOR     0 0 0
>           OUTLINECOLOR 255 255 255
>           TYPE      TRUETYPE
>           FONT      arial-italic
>           SIZE      8
>           ANGLE  [angle]
>           ANTIALIAS TRUE
>           POSITION  CC
>           PARTIALS  TRUE
>           ENCODING 'UTF-8'
>         END
>   END
> 
>   MINSCALEDENOM 100.0
>   MAXSCALEDENOM 5500.0
> 
>   PROJECTION
>   "init=epsg:27700"
>   END
> END
> 
> 
> many thanks
> 
> Tim
>