Projection woes

[Anonymous]

Hello,

I’ve gotten into a bit of a pickle. In my input data I used one projection (UTM 18), but the TIN was in a different projection (City of Ottawa, a Similar projection). It all looked fine before Hec-Ras. After all the processing work in Hec-Ras, the data comes out about 40 km east in the Ottawa projection, using UTM values. Basically it is still a UTM value using the Ottawa projection offset.

The real problem comes in the inundation mapping -> floodplain delineation stage. Since the xml/layers/tin aren’t all able to line up at the same location, the tool detects a null value and fails.

At this point I don’t see any other choice than to have the work recalculated in HecRas… Has anyone encountered this problem before?

[Chris G.]

Tim-

Yes, unfortunately you have to have everything in the same projection/coordinate system/datum for it to work in HEC-RAS.

[Anonymous]

How I do that, please explain, because I have same problem. I construct in arc map 9.3 using HEC GeoRAS, I projected all layer in UTM 49S then I import file to RAS file , actually for profile flood I used m3/s for input flood profile so in option I used SI (m) and I running the steady flow . After that I export to GIS file. I have problem when I construct flood deliniation. because they TIN was different with the bounding polygon and etc. I tried and reconstruct for several times but the results are same. Please help me with clearly explanation using jpg is more understanding

[jadams]

Go back to ArcGIS. Select your TIN and Export Data. When you give it a new name you should have an option to save the TIN with either the native projection or the same projection as the View Display. Change it to the View display. Now try to import the TIN again with RAS.

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