Hi,
Just to document some recent discussions with respect to the new tunnel attribute now available in WME, these are my understanding of the guidelines we will be using in Canada:
Tunnel attribute will be applied to road segments “that a bird wouldn’t fly in/under”.
Segments will be cut (node added) to delineate the start and end points of the tunnel.
The tunnel attribute and elevations are set on the tunnel segment only. I am thinking that tunnels under things such as rivers would be a negative elevation, but tunnels through mountains would maintain the “Ground” elevation. Is this correct?
I think these points raise some additional guidance for elevated roads and overpasses.
Segments will now be cut at the points of elevation changes rather than changing the elevation of the entire segment.
Segments at ground level should not be set to an elevation below ground, the higher/elevated road should be set to the correct elevation.
Finally, how big does a bridge need to be to be mapped? I’m thinking that small bridges over creeks shouldn’t be, especially if there is no real visual cue that you’re actually on a bridge. Should larger bridges with a visible above ground structure be mapped as a bridge? Should bridges only be mapped if there are other map elements underneath such as other roads or a body of water?
Please let me know if I have any errors in what I have here, or of there are other thoughts on the guidance.
Thanks
Kayos