Impedance functions - ObjectVision/GeoDMS GitHub Wiki
Network functions Impedance functions
There are four impedance functions:
-
impedance_table(...): when all given startPoints have to be considered as a single origin zone, resulting in:
- an
attributeDstZone->Impedance with the lowest route Impedance per destination zone (when no endPoints are specified: per Node). - optional attributes as sub-items depending on the used options.
- so the result is a table with, for each destination zone, the impedance of the shortest route from the nearest startPoint. In a bidirectional network this can be used to calculate the impedance from each location to the nearest destination by configuring the destinations as startPoints, see Impedance example origin to nearest destination.
- an
-
impedance_matrix when startPoints can relate to multiple origin zones, resulting in
- a
unit<uint32>reflecting the set of all or all found od-pairs - optional attributes as sub-items depending on the used options.
- a
-
impedance_matrix_od64(...), similar to impedance_matrix(...), but resulting in a
unit<uint64>in order to accommodate more than$2^{32} − 2$ od-pairs. - griddist using an implied network between neighbouring raster cell centers to do something similar to impedance_table(...) with less effort.
All these operations require at least the following four arguments:
- options : {∅} → String, a String parameter indicating function options, described below.
- impedance : Link → Impedance, a Measure (Float32 or Float64) attribute of Links with the Impedance per Link.
- f1 : Link → Node, a Node attribute of Link indicating the from node of each link.
- f2 : Link → Node, a Node attribute of Link indicating the to node of each link.
Note that Impedance functions can run different OrgZones in parallel, up to the number of cores of the running machine, as their tree growth is independent. This does not affect impedance_table, as that only grows one tree.
The following functions are deprecated in GeoDMS 19.x and obsolete in GeoDMS 20.x. They will be removed in GeoDMS 21.x:
| Obsolete function | Use instead |
|---|---|
dijkstra_s(...) |
[[impedance_table |
dijkstra_m(...) |
impedance_matrix |
dijkstra_m64(...) |
[[impedance_matrix_od64(...) |