I am having problem problems importing the two elevations into the sewer gems. So I want to ask that will not adding ground elevations affect the analysis or can I just add any arbitrary elevation to that some fixed number. Will it affect the analysis?
Yes, you can set the ground elevation to some arbitrary value above the highest pipes (say a million feet above sea level). and the hydraulic calculations will run. What you will lose in doing that is any information about sewer overflows. In additional, any profile graphs will look a bit silly (so don't use a million feet)..
It's not very difficult to import ground elevations from a variety of digital elevation model types. You may want to look into the wiki below.
Troubleshooting and Understanding TRex - Terrain Extractor tool
Answer Verified By: Sushma Choure