Wednesday, March 18, 2020

Custom geographic projections and HEC-RAS

This is my research report on using custom geographic projections with HEC-RAS 5.0.7. All my tests were based on the NAD83 AZ State Plane Central Zone 0202 International Feet (AZ83-CIF) projection.

Local reference point with no scaling

I set the local coordinates of Greenfield Road and Brown Road (N 886,670.326, E 755,001.784) to 1000,1000 using Civil 3D Units and Zone Transformation tab. No scaling to ground distances. 

I successfully transferred a terrain and a shapefile to HEC-RAS. 1000,1000 was at the same location in HEC-RAS.

I unsuccessfully added Web Imagery using Bing Satellite. My project appeared in the Gulf of California. The AZ83-CIF 0,0 point is in the Gulf of California, which indicates the Web Imagery was not added using the local transformation information. It was added using the unmodified AZ83-CIF projection. I got the same result with ArcGIS World Imagery and ArcGIS NatGeo World Map.

Local reference point with scaling

I got the same results as above when I added scaling. Terrain and shapefile came in correctly. Map Imagery did not.


If you want to use Web Imagery in HEC-RAS 5.0.7, you must use an unmodified published projection.

No comments: