Procedure HierarchyLevelSet(h2, h3, h4, h5: double);
Sets the 4 hierarchy parameters for use in hierarchical routing. Values should be expressed in the standard unit.
Input requirement: h2 >= h3 >= h4 >= h5 >= 0.
By default all parameters are set to infinite, meaning no hierarchy is applied.
We have executed tests with TeleAtlas (netbclass field) and Navteq (func_class field) databases and recommend these values:
|
Km
|
Miles
|
TeleAtlas
|
130, 120, 100, 22
|
81, 75, 62, 14
|
Navteq
|
145, 90, 40, 7
|
90, 55, 25, 4.4
|
Tests were executed on UK data with a large number of random routes. Compared to not using a hierarchy, calculations were 6 times faster with TeleAtlas data (0.3 secs per route) and 11 times faster with Navteq data (0.1 sec per route). Navteq has better hierarchy attributes and a little less details in the network, hence the differences.
For short routes (<50 km) there is only little difference between using a hierarchy or not, while calculation of longer routes (>400 km) in the UK may be as much as 20-40 times faster (NavTeq) and 6-30 times faster (TeleAtlas).
See also Hierarchical routing
ActiveX / VCL / CLX component: RWcalc