[processing] Endpoint distance threshold for network analysis

[nyalldawson]

Adds an optional end point distance threshold parameter to the network analysis tools. Previously (and still, by default) endpoints will ALWAYS be snapped to the nearest point in the network layer, regardless of how far away from the network they actually are. This can result in meaningless results, as the tools will happily snap points to a road hundreds of kilometers away :)

Now, there's an optional end point distance threshold parameter for these tools. The behaviour of the threshold depends on the algorithm:

• For the “Service area (from layer)” tool an optional new output was added for “non routable features”. This output will contain any features which were deemed too far from the network. All other features which are within tolerance distance to the network will be stored in the standard output from the tool.
• For the “Service area (from point)” tool an error will be raised if the point is too far from the network
• For the “Shortest path (point to point)” tool an error will be raised if either the source or destination points are too far from the network.
• For the “Shortest path (layer to point)” and “Shortest path (point to layer)” tools:
  • An error will be raised if the point is too far from the network.
  • A new optional output was added for “non routable features”. This output will contain any features which were deemed too far from the network. All other features which are within tolerance distance to the network will be stored in the standard output from the tool.

Sponsored by City of Canning

[qgis-bot]

@nyalldawson
This pull request has been tagged as requiring documentation.

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[qgis-bot]

@nyalldawson

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[qgis-bot]

@nyalldawson
A documentation ticket has been opened at qgis/QGIS-Documentation#9029
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