I am trying to create contour lines and filled contours from a shapefile of height points using the contour plug in (have tried other tools but with no success).
The data is sourced from the UK Ordnance Survey in tiles of 400 x 400 points (NTF format). Each tile has been opened as a vector layer and then saved as a shp layer. The plug in will run properly with a single tile. However, the area I need is 3 x 3 tiles i.e. 1200 x 1200 points.
Initially I generated contour lines and filled contours for each of the 9 tiles. This is unsatisfactory since the spacing is slightly different for each tile according to its height range resulting in mismatch at tile boundaries. I then merged the 9 shp layers using the mmgis and vector menu merge. Running the contour plug in against either merged file fails with the dialogue box showing 'Not Responding'.
I am running QGIS 1.8 Lisboa on Windows 8 x64 pro with 32gb of memory and plenty of free disk space on all drives. I have had no problems with other imported layers, adding new layers of data. However, this is the first time I have attempted to generate a shaded layer or contour lines. I guess there must be a setting somewhere to allow the plug in to handle the larger data block - I found and increased the cache setting in 'options') or I am using the wrong tool for the job.
My project is mapping local history routes/settlements. The shading is needed to provide context.