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Sets the 4 hierarchy parameters for use in hierarchical routing. Values should be expressed in km.
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 TomTom (net2class field) and HERE (func_class field) databases and recommend these values:
HERE tests were executed on UK data with a large number of random routes. Compared to not using a hierarchy, calculations were 11 times faster.
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 (HERE).
We have not had time to test TomTom so accuractely yet, so the values above are just a good starting point.
In any case your dataset should have hierarchy data included and prepared in the corresponding bits in the attribute field.
Syntax: SetHierarchyLevel(h2, h3, h4, h5: double)