Networks & Routing

Distance along the street, not across the rooftops.

The network analysis path, from a street network as a graph to travel-time isochrones. distance along the street, not across the rooftops1streets as a graphnodes and edges2build & snapwhere errors enter3shortest pathone, then many4isochronesand their assumptionsThe snap at stage two is where nearly every absurd routing distance is created

Straight-line distance is a decent proxy until a river, a railway or a one-way system says otherwise — and then it is wrong in exactly the places the analysis is about. These guides build a routable street graph from OpenStreetMap, snap real addresses onto it, measure shortest paths by distance and by travel time, scale to thousands of origin-destination pairs, and cut travel-time isochrones — with the disconnected components and unit mix-ups that produce confidently wrong answers.

The route is deliberately front-loaded with building and snapping rather than routing. Dijkstra is a solved problem; attaching your points to the right edge of the right street is not, and it is where nearly every absurd result in this subject comes from.

Start here

The cornerstone guide — the whole workflow end to end. Everything after it goes deeper into one part of it.

Step 1 Street Networks as Graphs Explained street network graph explained Begin the path →

The full path, in order

The concepts underneath the work, then each task, then the errors that task produces. Work down, or jump to the step you need.

  1. How to Build a Street Network Graph in Python with OSMnx street network graph python ⚙️ How-To
  2. Network Distance vs Straight-Line Distance Explained network distance vs straight line 🧭 Concept
  3. How to Snap Points to a Street Network in Python snap points to network python ⚙️ How-To
  4. How to Calculate the Shortest Path Along a Street Network shortest path street network python ⚙️ How-To
  5. NetworkX Says No Path Exists Between Two Nodes networkx no path exists 🔧 Fix
  6. Street Network Routing Returns Absurd Distances routing wrong distance 🔧 Fix
  7. How to Measure Network Distance for Many Origin-Destination Pairs network distance matrix python ⚙️ How-To
  8. Isochrones Explained: Travel Time Areas and What They Assume isochrones explained 🧭 Concept
  9. How to Generate Isochrones in Python generate isochrones python ⚙️ How-To

Topics this path covers

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Networks & routing Geometry & topology Joins & relationships Maps & visualisation Data sources & downloads CRS & projections

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