Network Reachability Map
Explore how far a supplied road or path network can be traversed within a time or cost budget. Dijkstra finds the least cost to each node using the declared one-way and two-way links. Each edge is then split into reachable and unreachable fractions, including a gap between two reachable ends. The network, costs and coordinates come from you; this browser tool does not fetch roads or claim real navigation accuracy.
Key features
- Strict local graph JSON validation for up to 80 WGS84 nodes and 240 directed/two-way edges
- Dijkstra shortest costs including alternate paths and zero-cost links
- Reachable edge intervals and up to two interior budget boundaries per link
- Distinct outside-budget and structurally disconnected nodes
- Straight-segment SVG preview plus GeoJSON, CSV and validated project JSON downloads
How to use
- Open a local graph JSON file, paste JSON, or load the self-created example. Each edge declares its direction and nonnegative time or cost.
- Choose a starting node and a budget in the graph unit.
- Calculate shortest costs and inspect the reachable nodes, full links, partial links and disconnected count.
- Read percentage intervals along partial links; a two-way link can have separate reachable intervals at both ends.
- Download the SVG preview, GeoJSON reachable segments and boundaries, or CSV tables.
Use cases
- Sketch a walkable area from a user-provided trail graph and estimated minutes
- Inspect which links of a one-way campus path remain within a travel budget
- Compare alternate routes and reveal an unreachable middle on an expensive two-way link
- Audit disconnected nodes and invalid negative edge costs before publishing a network
Frequently asked questions
Does this fetch real roads or live traffic?
No. All topology, coordinates, directions and edge costs must be supplied in the local JSON. The SVG draws straight segments between node coordinates; it is not a routing service or real-road isochrone.
How are one-way and two-way roads handled?
A one-way edge can be traversed only from its from node. A two-way edge creates both traversal directions; reachable parts may grow from both ends and leave an unreachable center.
How is a partial-edge boundary placed?
The remaining budget is divided by that edge’s cost and interpolated linearly between endpoint coordinates. This assumes uniform cost along the visual straight link; real road geometry and travel-time variation are not modeled.
What is the difference between outside budget and disconnected?
An outside-budget node has a finite graph path whose shortest cost exceeds the budget. A disconnected node has no permitted directed path from the start at any cost.
Are negative and zero costs supported?
Negative costs are rejected because Dijkstra is not valid for them. Zero-cost links are accepted and can be reached even with a zero budget.
Are my graph files uploaded?
No. Parsing, calculation and downloads run in this browser tab. The tool makes no external map-tile or routing request.
Privacy
Graph JSON stays in the browser tab. No road provider or routing service is contacted.
Comments & questions