Editing vector layers with Quantum GIS
I’ve been looking around for an open source alternative to the excellent Desktop GIS Mapping Application MapInfo Pro. I’ve installed and played with both Quantum GIS (QGIS) and MapWindow. The latter is a little bare bones and does not seem to include any geometry editing, so I’ve been focussing instead on QGIS.
QGIS is a great application, though it is quite noticably slower to render very large mapping layers than MapInfo Pro. However – and this is, strangely, not very well known or documented – QGIS will only let you edit layers which are Shapefiles. There is no documentation that I can find which says why the “Toggle Editing” function is always disabled for other files – this is very confusing/frustrating if you don’t know about this Shapefile limitation.
There is a converter within QGIS (which is really just a UI on ogr2ogr) to convert between TAB and SHP formats, but Shapefile layers are rather limited because you can’t mix geometries within a layer – both nodes (points), and lines, for example. This is rather a problem because the map data I have has both points and lines – the points are needed to style the line endpoints and allow for data attributes on them. Separating points and lines into different layers in this context is a bit of a pain. Shapefiles also have various other limitations – for example, field names can be no longer than 10 characters.
Perhaps hooking up QGIS to an SQLite database with Spatialite extension might make managing the map data layers more streamlined – one for a rainy day…
It is not true that QGIS is able to edit only shapefiles. There are plenty of other formats including PostGIS and SpatiaLite that have writing capabilities.
For file-based layers QGIS uses OGR library and if the library does not include write support for a particular format, neither QGIS can write it.