QGIS Track Editing
- QGIS is able to merge multiple line features into a single line, using Edit > Edit Geometry > Merge Selected Features.
- QGIS does not automatically close gaps when merging lines. Before merging, a third line needs to be created, snapped to the endpoints of the gap.
- The merge functionality provides a dialog allowing selection of which pre-merge feature each attribute should come from for the merged feature. Be careful to make sure the earliest utc_start and latest utc_stop are selected.
- If columns need to be reordered in the future, QGIS can do so with Processing > Toolbox > Vector table > Refactor fields.
LineString vs. MultiLineString
GPX files allow multiple disconnected track segments (trkseg) in the same track, effectively replicating the functionality of a MultiLineString. Although entire process is set up already to split disconnected segments into their own tracks, some GIS software has difficulty with LineStrings crossing the 180th meridian, so each track should still be stored as a MultiLineString so it can be split at the 180th meridian if necessary.
GeoPandas
- GPX and KML can relatively easily be converted to a GeoPandas GeoDataFrame, which can then be appended to a GeoPackage table using
GeoDataFrame.to_file(mode='a'). - to_file uses Fiona, which requires columns to match when appending a GeoDataFrame to a layer. We have to be careful to ensure the import scripts and GeoPackage file use the same column structure at all times.
- We will need to define our columns and create a template file (stored within the gps_log_tools repository at templates/driving.template.gpkg). The import scripts can then check if a driving log GeoPackage file already exists, and copy it from the template if not.
- Appending to a layer within a file does not overwrite other layers. This means we could potentially store rental car data and other data in the GeoPackage as well.