QGIS 6 Data load
This is where it happens. Prepare to be bewildered.
Protect base map‐data
If you have not done so already, put the map‐data somewhere categorised and named. QGIS will work from it directly, not load into memory. If you leave the data in a temporary or download location, if the data is moved or deleted, projects will fail to load.
Add map layers
Like this,
Layer > Add > Vector Layer
Set Source Type = ‘directory’. Under ‘Vector Dataset’, navigate to a Shapefile folder. Then ‘Select All’. Tick ‘Add tiles to group’ Then ‘Ok’.
This may spew a warning about the Coordinate Resolution System. In most cases, you can ignore this warning—it’s only about a small loss of accuracy (if the warning irritates, follow the steps below). Then press ‘Ok’
This should load the data. I’d take the positives here—QGIS loaded a Shapefile, reported no errors, then displayed a result. Unfortuately, QGIS will use a generic style for the data loaded. If your style looks like mine, the display now looks like you you’ve damaged your visual system. Try to ignore this, and let’s concentrate on something else—navigation of the map.
Coordinate systems
It’s likely that an initial load of map data into QGIS will return warnings about the coordinate system. In my older version of QGIS, I was nagged like this,
For a more accurate transformation see OSGB 1936 / British National Grid to ETRS89 (2) (code 1039): contact the Ordnance Survey of Great Britain (http://www.gps.gov.uk/gpssurveying.asp) for details...
This means the transform installed in QGIS for a current ‘British National Grid 1936’ is not up to date. As discussed in the step coordinate and projection systems, this is not damaging or important, but the continued warnings irritate.
To fix this I needed to download from https://download.osgeo.org/proj/proj-datumgrid-europe-1.5.zip. In the download, find the file ‘OSTN15_NTv2_OSGBtoETRS.gsb’. Then follow thee directions on the load warning. This will install the transform and make it available in menus. You will need to restart QGIS.
If you loose a load‐warning, I think you can install the transformation file using,
Project > Properties > CRS
But I’ve not tested.
End of data load
Right. How do we do the most basic operations on this huge lump of data?