Build Map

In this step, we fetch roadnet and aois data within the area intended for simulation from OpenStreetMap and process these data into GeoJSON format, finally we process this roadnet GeoJSON file and AOI GeoJSON file into our own Protobuf Map format. .

Generate the Map format output

from mosstool.map.osm import RoadNet, Building
from mosstool.map.builder import Builder
from mosstool.util.format_converter import dict2pb
from mosstool.type import Map

rn = RoadNet(
    proj_str="+proj=tmerc +lat_0=22.54095 +lon_0=113.90899",
    max_latitude=39.92,
    min_latitude=39.78,
    max_longitude=116.32,
    min_longitude=116.40,
)
roadnet = rn.create_road_net("cache/topo.geojson")
building = Building(
    proj_str="+proj=tmerc +lat_0=22.54095 +lon_0=113.90899",
    max_latitude=39.92,
    min_latitude=39.78,
    max_longitude=116.32,
    min_longitude=116.40,
)
aois = building.create_building("cache/aois.geojson")
builder = Builder(
    net=roadnet,
    aois=aois,
    proj_str="+proj=tmerc +lat_0=22.54095 +lon_0=113.90899",
)
m = builder.build("map_name")
pb = dict2pb(m, Map())
with open("data/temp/map.pb", "wb") as f:
    f.write(pb.SerializeToString())

• Here max_latitude, min_latitude, max_longitude, min_longitude describe the bounding box of the area from which data is to be obtained from OSM, and all are in WGS84 coordinates.

• proj_str is a PROJ.4 projection string, used to transform longitude and latitude coordinates into planar xy coordinates. Generally, if there are no special requirements, the proj_str can be directly set to a Transverse Mercator projection centered on the map’s center, which is f"+proj=tmerc +lat_0={(max_latitude+min_latitude)/2} +lon_0={(max_longitude+min_longitude)/2}". And must remain the same during this process.

It’s worth noting that the features in output GeoJSON file of create_road_net() and create_building() remains in WGS84 coordinates. The provision of proj_str is because using planar xy coordinates is more precise than latitude and longitude coordinates when handling the internal topological relationships of the road network.