Networking without elevation

[SophiaRuger]

I am aiming to create a network with arcgis pro 2.8  and I cannot find a network dataset with road elevations. Will it ruin the network if I do not have elevations (F_ZLEV and T_ZLEV)?

[MelindaMorang]

When you create a network dataset using the Create Network Dataset tool, you can choose which type of elevation model you want to use: No elevation, Z-level fields, and 3D Z coordinates.  If your data is 2D and does not have Z-level fields (FZLEV and TZLEV), then you would need to create the network using no elevation.  This will still produce a valid and usable network dataset.  You just may have some problems modeling overpasses and underpasses.  You will want to carefully check those to make sure they don't have endpoints or vertices (depending on your connectivity policy) to prevent them from connecting at those locations (so the driver can't turn left off a bridge and start driving on the road that goes under it, for example).  But as long as the roads don't meet at an endpoint/vertex at the location where they cross, it should still work just fine.

Here's some documentation that should help: https://pro.arcgis.com/en/pro-app/latest/help/analysis/networks/understanding-connectivity.htm

[mohanalogakrishnan]

I am new to this forum. I am not sure if I can raise a question this way as you are answering to a network problem. I have elevation fields defined for the road line segments to represent under and over pass (0 overpass and -1 underpass level). I have seen road network building videos where people use From and To Elevation fields. How should I use the existing elevation_fields in my network building wizard. Similarly, I dont have F_Node and T_Node in my road dataset. I am trying now to understand how this whole process works. I appreciate your views on this matter.

[MelindaMorang]

The key is that you need two fields, not one.  The field values represent the "level" of each endpoint of the feature.

For instance, let's suppose you have an overpass and underpass with endpoints at the location where they cross (four features total with eight endpoints).  Because your data is 2D, it looks something like this:

But really, it's an underpass/overpass situation, and you don't want the roads to connect where they intersect.  To do that, you need to add fields like F_ZLEV and T_ZLEV and assign them different elevation values to ensure that they don't connect.  For example, set the overpass values to 0 and everything else to 0.

The hardest part is figuring out whether to set F_ZLEV or T_ZLEV to 1 because the correct field to use depends on the direction of digitization of the street feature.  The F_ZLEV field describes the level of the "from" endpoint  (the starting point of the feature), and the T_ZLEV field describes the level of the "to" endpoint (where the feature ends).

[mohanalogakrishnan]

Thank you so much for taking time to reply. I understood what has to be done. Thanks again.

[Amarz]

If your roadway network doesn't have From Elevation and To Elevation fields, review the 'Group Connectivity' settings. I have a similar situation and have to use the 'Endpoint' option vs the 'Vertices' option.