By David Crowther
Question:
After running the GML Tiler, there are some missing tiles, what is causing this?
Answer:
Having ran the GML Tiler on your OS Mastermap database, you will have a series of Web Map Tiles (WMTS) which can then be used to render OS Mastermap in you chosen GIS e.g. Cadline’s webGIS – MapThat.
However, on rare occasions you may find that there can be some missing tiles in the map.
Why is this?....
The GML Tiler tool reads in the Ordnance Survey Mastermap table features, using a Feature Code to style each feature based on their code e.g. Building, Road, Rail etc…. As the Tiler reads in the OS features, it then creates .PNG tiles styled according to the data in the map extents, for each zoom level you chose.
So, the likely reason for the missing tiles is because the Ordnance Survey have introduced a new feature code that is not currently recognised in the GML Application…..
… and so, in the example above the OS Mastermap data for this area has a new Feature Code for type = ‘RAIL POINT’. Because this Feature Code is not stored in the GML Application, the GML Tiler will not know what style options to use to colour those features. Thus, the tiles for the affected area will be skipped, leaving gaps between the tiles to the left and right.
The solution to this issue is to contact Cadline and let us know the coordinates of the affected area. Cadline will then investigate if there are new Feature Codes for this area and insert those Feature Code records into the styling tables within your GML Database. Once the new Feature Codes are available, in this case ‘RAIL POINT’, you can re-run the Tiler to create the missing tiles.
Tip – when you re-run the Tiler, in step 5 you can edit the Min/Max Long & Lat values to only create tiles for the missing extent area, instead of running all the tiles again!
The GML Tiler will now create the tiles again for the chosen affected area….
…. now simply copy and paste the new tiles into your MapThat Mashups location…. And the next time that you open MapThat, the mapping will now render the newly created tiles.