Sunday, 31 May 2015

Some more work in progress re: Cornish GIS maps

Here is a little more about my work in progress in generating maps of Cornwall in QGIS.

I have downloaded various Ordnance Survey VectorMap data, along with some layers which come from OpenStreetMap. The OS VectorMap has layers including woodland, tidal water, surface water polygons (e.g. lakes and reservoirs), foreshore and surface water lines (rivers etc.) and others.

These is more comprehensive than OpenStreetMap, however the OpenStreetMap vector layers come with names associated with them in the attribute table in some cases. Certain of the OS VectorMap layer objects will exist in the VectorMap 'Named Places' shapefile, but as points rather than as names in the attribute tables of the polygons themselves.

In the map below I have used the woodland polygons from the OS VectorMap and the ones from OpenStreetMap, but only the OpenStreetMap ones are labelled, since only they have names in the table.

I have also generated contours based on the Shuttle Radar Topography Mission, 1 arcsecond data, which is now freely available for most of the world. It is also possible to use OS Terrain50 contours, which generally appear smoother than these ones, however given these are released in individual squares, I found myself having so many vector layers in the rendering that QGIS crashed.

The Falmouth area, using contours from SRTM 1 arcsec
There is a fairly large amount of data entry to be done to put the names in Cornish, and beyond the list that has already been published by MAGA I would expect it to be slower work.

The OS VectorMap Named Places shapefile for the SW grid square has 2759 entries, of which 679 are various geographic features and the remainder are populated places.

The OpenStreetMap files have approximately 122 named woodlands in Cornwall (of 810 polygons, of over 9000 in the SW grid square alone for OS VectorMap), 56 named water polygons (of 327), 21 parks (of 45), 242 named waterways (of 2923) as lines (some duplicate names for different parts of a feature), and 1337 named places (of which I have already entered 421 in Cornish based on the MAGA Kernow list). There are 10342 named roads in Cornwall from the Open Street Map data.

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