Hi Marek, This is a way of making arcs in Mapserver that is based on using VRTs and sql The data source doesn't need to be in spatialite though. It can be a shapefile or a CSV file or anything that gdal can handle.
Simon Mercier at Mapgears and I developed this for making litehouse circles for Sea charts a couple of years ago. In the current version of the SMAC-M project this is done with preprocessing in another way. But I still like the idea that You can draw anything with sql. I was going to make a small separate example this morning. But I ran into some problems. It seems like my current gdal is not compiled with a version of libspatialite that should use librttopo instead of the lwgeom. In the version I used before I had the sql function ST_project. In the version I had today on my machine and in some docker containers I didn't. I guess I have to build a gdal-mapserver with the right libspatialite and librttopo versions where I can do these trix again some time. Anyway this is the VRT file that can draw an arc in Mapserver. The data source contains points in EPSG 4326 and we are drawing the arc in EPSG 3857 in this case. valnmr is the radius and sectr1 and sectr2 are starting and ending angles of the arc. To use the vrt in mapserver you use: CONNECTION "arc.vrt" CONNECTIONTYPE OGR DATA "arc" ###### arc.vrt ##### <OGRVRTLayer name='arc'> <SrcDataSource>coastal.sqlite</SrcDataSource> <SrcSQL dialect='sqlite'> SELECT rcid,fidn,valnmr,sectr1,sectr2,colour,SIGGRP,SIGPER,HEIGHT, MakeArc(ST_X(Transform(Geometry,3857)),ST_Y(Transform(Geometry,3857)), GLength(Transform(MakeLine( MakePoint( X(Geometry), Y(Geometry),4326), ST_Project( MakePoint( X(Geometry), Y(Geometry), 4326 ), valnmr*1852/10, Radians( sectr1-180 ))),3857)), (180-(sectr2-90)),(180-(sectr1-90)),3857,2) AS geometry FROM lights_point WHERE sectr1 NOT NULL AND sectr2 NOT NULL AND sectr1!=0 AND sectr2!=360 </SrcSQL> </OGRVRTLayer> ####################### If You would like to check what version of various libraries that You have, You can use this VRT and run ogrinfo on it. E.g ogrinfo debug.vrt debug ##### debug.vrt ##### <OGRVRTDataSource> <OGRVRTLayer name='debug'> <SrcDataSource>coastal.sqlite</SrcDataSource> <SrcSQL dialect='sqlite'> select sqlite_version(), spatialite_version(), lwgeom_version(), geos_version(), proj4_version() FROM lights_point </SrcSQL> </OGRVRTLayer> ##################### Have fun ! Lars Schylberg
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