Straightness centrality interpretation - Results Exporting

[mohdalattar]

Greetings,

The main issue of this discussion is that I am skeptical about Straightness centrality results. So I would like you to verify my procedure or if you can explain to me why I am getting these results.

My code is

import geopandas as gpd
import momepy
import osmnx as ox
import matplotlib.pyplot as plt

G = ox.graph_from_place(“Santa Monica, California, USA”, network_type=“all”)
G_projected = ox.project_graph(G)

edges = ox.graph_to_gdfs(ox.get_undirected(G), nodes=False, edges=True,
                                   node_geometry=False, fill_edge_geometry=True)
primal = momepy.gdf_to_nx(edges, approach=“primal”)
primal = momepy.straightness_centrality(primal)
nodes = momepy.nx_to_gdf(primal, lines=False)
momepy.mean_nodes(primal, “straightness”)
primal_gdf = momepy.nx_to_gdf(primal, points=False)
primal_gdf.to_csv("SM.csv")
ox.save_graph_shapefile(G_projected, filepath=“SantaMonica”) 

Then I join the CSV file with the Shapefile from OSMnx. I am getting the following:

My questions are:

• I am expecting to have relatively similar straightness centrality score for all grid-like streets. Not sure why this variation in the straigthness centrality.
• Is there a better way to export the results ? How can I incorporate ox.set_edge_attributes function to export a shapefile with the results of straightness centrality.

Thanks

[martinfleis]

Hi, sorry for a long delay.

A few points.

You have probably noticed this warning.

UserWarning: Geometry is in a geographic CRS. Results from 'length' are likely incorrect. Use 'GeoSeries.to_crs()' to re-project geometries to a projected CRS before this operation.

Since straightness is based on a distance, you need to make sure you are using the G_projected in ox.graph_to_gdfs, not G as you have in your code.

But even with the code as you have it, the result is this:

You have used Equal count binning which likely confused you. There's very little variation in fact, apart from that highway in the middle.

Is there a better way to export the results ?

Yes, you can save it directly to shapefile or any other GIS file format.

primal_gdf.to_file("my_file.gpkg")