Export

It’s often useful to export segments and assessment results to other formats for visualization, and the class provides two methods to support this. The save method saves a network to a vector feature file, and the geojson method converts a network to a geojson.FeatureCollection.

Note

The examples on this page are for ShapeFiles, but pfdf supports most common vector file formats. Refer to the vector driver guide for more information on supported formats.

Export Types

Both methods support 4 types of export:

Type	Description
segments	Stream segments as LineString geometries
basins	Terminal outlet basins as Polygon geometries
outlets	Terminal outlets as Point geometries
segment outlets	All outlets as Point geometries

By default, both methods will export segments, but you can use the “type” option to select a different type:

# Save segments as LineStrings (default)
segments.save('segments.shp')

# Save basins and outlets (Polygons and Points)
segments.save('basins.shp', type="basins")
segments.save('outlets.shp', "outlets")
segments.save('all-outlets.shp', "segment outlets")

Properties

Both methods allow an optional properties input, which can be used to tag the features with associated data values. The properties input should be a dict whose keys are the names of data fields (as strings), and whose values are 1D numpy arrays with one element per exported feature. Each array should have an integer, floating-point, boolean, or string dtype. There are no required data fields, so you may use any data field names supported by geojson. However, note that data field names may be truncated when saving to certain vector file formats (for example, saving to a Shapefile will truncate field names to 10 characters):

# Export segments and include data properties
properties = {
    "id": segments.ids,
    "hazard": my_assessment_results,
    "catchment_area": segments.area(),
    "legend": ["Low hazard", "Moderate hazard", ...],
}
segments.save('segments.shp', "segments", properties)

If you are exporting basins or outlets, then the property arrays may optionally have one element per local drainage network, as opposed to one element per segment. Either case is allowed, and the terminal outlet values will be extracted as needed.

# Export basins and include data properties
basins = segments.isterminus
properties = {
    "id": segments.terminal_ids,     # One element per terminal segment
    "hazard": my_assessment_results, # One element per segment
}
segments.save('basins.shp', "basins", properties)

CRS

By default, both methods will export the features using the CRS of the flow-direction raster used to derive the network. However, you can use the crs option to export the features to a different CRS instead:

>>> # Default would export to EPSG:26911
>>> segments.crs.to_epsg()
26911

>>> # But this will export to EPSG:4326 instead
>>> segments.save('segments.shp', crs=4326)

__geo_interface__

The class also supports the __geo_interface__ protocol:

geojson_dict = segments.__geo_interface__

This returns a dict-like geojson.FeatureCollection, and is equivalent to calling the geojson method for segments with no properties:

# Same output
geojson_dict = segments.__geo_interface__
the_same_dict = segments.geojson(type="segments", properties=None)