Point-to-point

Point-to-point is used to find the distance between two points on LineString and Link items and the perimeter of Polygon items.

You will see a route drawn between the points. To use this command, ensure the items intersect and are on an editable or hittable overlay.

Select Analysis > Routing > Point-to-point.

This offers you three options: SIS, OSRM or Valhalla:

1. SIS

Select one of the point-to-point options.

  1. Shortest - Finds the shortest route. This method can be used with any geometry.
  2. Well-known cost expression- choice of well-known mapping networks.
  3. User-defined cost Expression - Customise your expression to find an optimum route. For example, use "_length#" to achieve the same effect as the Shortest option, but only using the Link item geometry. This method only works with Link/Node topology.

Routing Restrictions

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Point-to-point

Routes can be measured on external data such as Ordnance Survey MasterMap

Be aware however with OS MasterMap digitising styles, you will often find what appears to be a single LineString item is in fact made up of several shorter LineString items).

You can also route find on LineString items created with LineString and Freehand and on the outlines of closed Polygon items.

For example:

Route-finding is especially powerful with topology where routes can be found across a link and node network. The route can also be based on a chosen expression.

  1. Select Point-to-point to display the Route dialog (shown above).
  2. Select how the route should be measured:
  3. Check the Create a Line Item tickbox if you want to create a new LineString item along the found route. his enables you to store the geometry of the route as a permanent item for future use.

To define a route on a vector network from point A to point B SIS Desktop will find a route across the network, generate the LineString item and place it in an editable overlay:

In this case the LineString item's length is expressed as an attribute:

Route options

Custom Expression

Finds the 'cheapest' route using the expression as the 'cost' of a Link, over any Link/Node network.

2. OSRM - Well-known

OSRM uses a custom database and creates routes faster than the other options. The custom databases can be created using the OS Network Manager. The custom databases are stored in the OSRM folder of the SIS Desktop 9.1 installation.

Greater London

Finds a route over the road network in an extract of the OpenStreetMap database for Greater London, using the 'car' profile.

Hertfordshire

Finds a route over the road network in an extract of the OpenStreetMap database for Hertfordshire using the 'car' profile.

3. Valhalla

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