Exporting GeoTIFF from GM V23.0 to HEC-RAS

CarrickCon

G'day,

I realise that this is a problem due to a recent change in US Army Corps' HEC-RAS software from V5.0.7 to V6.1.0 but was hoping that some bright spark on this forum could perhaps help me export rasters from GM correctly... (HEC-RAS is free to download at: https://www.hec.usace.army.mil/software/hec-ras/download.aspx )

Previously I could export a raster as .tif from GM and import to HEC-RAS V5.0.7 no problem (see first screen grab & .jpg below). Now when I open exactly same .tif file in V6.1.0 it applies some crazy kind of classification system to it (doesn't seem to be elevation or slope based?) and displays it in a pixelated fashion ((see second screen grab & .jpg below). Note classification legend on RHS.

Does anyone know if there an alternative way to export a .tif so HEC-RAS V6.1.0 will display it simply as an image? I've tried all other raster export formats in GM and either they don't display at all in V6.1.0 or they have the same crazy classification/pixilation problem.

Alternatively is there a way to export a raster form GM a simple tiff not a geotiff?

Kudos to whoever can help!

Cheers,

/al

HEC-RAS V5.0.7 Screenshot.jpg

HEC-RAS V6.1.0 Screenshot.jpg

CarrickCon

Hi Mike,

Thanks for following up on this - much appreciated. Unfortunately the good folks at USACE don't offer support to non-military users like myself.

I have tried just about every every possible combination of options in the GM V23.0 GeoTIFF export dialogue box to no avail.

However - great news - I have discovered the joys of NITF format which imports into HEC-RAS V6.1.0 no problem! I didn't even know what NITF was until I searched it up this morning, but given that  it was developed by U.S. Department of Defense and Federal Intelligence Community I should have know that it would work seamlessly with USACE software.

Cheers,

/al

bmg_mike

While I'm not sure about the HEC-RAS issue, there is an option on the GeoTIFF Export Options dialog in GM to leave off the GeoTIFF header (ADVANCED: Don't Write GeoTIFF Header). I'm not sure if that is what is causing the issue though since that is mostly position data, the low-level image characteristics are in the base TIFF tags.

CarrickCon

Hi Mike,

I appreciate the feedback, but unfortunately that didn't help.

I guess I need to find another way of generating a simple TIFF...

Cheers,

/al

bmg_mike

I wonder if it is some other setting on export that is causing HEC-RAS to interpret the image oddly. What type of GeoTIFF are you exporting (i.e. 8-bit palette, 24-bit RGB, multi-band)?

Also, are you checking the option to mark background pixels as transparent? This would add an alpha band to image. It almost looks like you are saving a 24-bit RGB image with an alpha band and HEC-RAS is treating it as a 4-band CIR or something.