bw2regional.topography

Module Contents

Classes

Topography

A topographical description of a geocollection.

class bw2regional.topography.Topography

Bases: bw2data.DataStore

A topographical description of a geocollection.

A topography must be registered to exactly one geocollection.

For example, the geocollection ‘countries’ could have the location ‘Ghana’, and include a spatial data file which defines ‘Ghana’. The Topography ‘countries-topo’ would have two files:

1. A mapping file that linked each location in the geocollection ‘countries’ to a set of topographical faces

2. A spatial dataset which defines the topographical faces

Topographies can make some calculations much quicker for two reasons:

1. Large features are split into smaller faces, making GIS calculations easier and spatial index queries more efficient, as bounding boxes are smaller

2. You only do GIS work on each topographical face once

The LCA classes in bw2regional don’t work directly with the Topography objects; rather, GIS calculations on topographies can be merged to the spatial features of the geocollection.

The usual order of operations with a geocollection that has a Topography is the following:

1. Create a geocollection, including defining a spatial dataset

2. Create a new topocollection and specify the linked geocollection. You can also optionally define another spatial dataset, using the same format as for geocollections.

3. Instantiate the new Topography object created in the earlier step, and write mapping data from spatial features in the geocollection`(s) to face ids in the `Topography spatial data set.

The data format for mapping data is {feature field value: [list of topo field values (usually id numbers)]}.

Here is a code sample for using the test data in bw2regional:

from bw2regional import Topography, geocollections
import json

geocollections['countries'] = {
    'filepath': os.path.join(data_dir, "test_countries.gpkg"),
    'field': 'name'
}
topocollections['countries-topo'] = {
    'geocollection': 'countries',
    'filepath': os.path.join(data_dir, "test_provinces.gpkg"),
    'field': 'OBJECTID_1'
}
topo = Topography('countries-topo')
topo.write(json.load(open(os.path.join(data_dir, "test_topo_mapping.json"))))

property geocollection

_metadata

add_geomappings(data)

write(data)