DEM data in float format

[Approach_Medium]

Hi;
I have just updated my copy of TransDem Trainz to ver 2.3.1, and it now supports the USGS "float" format for DEM's. Thanks Ronald! I wasn't expecting that fix so soon.
So I downloaded several grid squares in NY state at 1Arc in the Float format. I extracted the .zip file, then opened TransDem and browsed to the folder where I had extracted the data.
I found 6 files with the .adf extension that were available to TransDem.
It appears that no matter which one I open, I get the same DEM image. When saving the .dem file in TransDem, the default finename is the same as well. One of the files is much larger; 54MB compared to one other that is 100KB and the rest are only 1KB. I assume that the smaller files are automatically loading the larger file. When I selected the area for download, I ticked only the DEM data.

Anyone with info on this?

Thanks, and have a happy!

FW

 

[SharkNose]

Be sure you are downloading the "ArcGrid" format for 1 arc and 1/3 arc second data. That is what Roland updated TransDEM for. I don't think it reads the "float" format yet. You can still get 1/9 arc second data in GeoTiff format (at least for a while still).

Andrew

 

[Approach_Medium]

That's interesting. I thought I had downloaded float format, yet it did open in TransDem. I'm going to check this out further.
Thanks

FW

 

[SharkNose]

My apologies. I may have misunderstood your original post (darn egg nog!). From Roland's recent tutorial page: "In TransDEM, open any of the '.adf' in that subdirectory. TransDEM will process all other files of this DEM automatically."

That may be more of the answer you were looking for.

The full tutorial is at GEO Data - USA.

Andrew

 

[Approach_Medium]

My apologies. I may have misunderstood your original post (darn egg nog!). From Roland's recent tutorial page: "In TransDEM, open any of the '.adf' in that subdirectory. TransDEM will process all other files of this DEM automatically."

That may be more of the answer you were looking for.

The full tutorial is at GEO Data - USA.

Andrew

Yes. That is what I found by experimentation. I also noticed that with the latest release of TransDem (ver 2.3.1.0), opening a .kmz file for georeferencing is done automatically when the .jpg file is opened, provided the two files have the same name. This eliminates the need to hit the Alt-R keys. When processing many data files one after another, this seemingly minor convenience becomes a major time saver!
Now if I could only get some consistency from the USGS TNM server. Sometimes it doesn't want to put a selection into the "cart"; just sits there with the dialog open indicating that it is doing something, but taking much longer than I can accept. When this happens, the download cannot be completed. Need to wait for another time to try. I haven't figured out how to save selections for later download. There doesn't seem to be a feature that would allow a user to create an account. Having to type in my e-mail address for each set of requests is a pain... Maybe someone can help me here too...

Thanks.

Fw

 

[Approach_Medium]

Does it make a difference whether or not the "grid width utm" matches for all sections of a DEM that are being added together to create one larger DEM?
The first section I opened from the .adf file came in at default grid of 25. Then, subsequent files opened with default 20, so I changed it to 25 to match the first one.

Thanks for your help

FW

 

[SharkNose]

I think that has to do with the resolution of the DEM. Subsequent DEMs, if you are merging them together into one DEM, will automatically adjust to the resolution of the first DEM you opened.

Another quote from Roland, "Yes, you can mix higher and lower resolution. Always start with the higher resolution and then merge adjoining lower resolution DEMs into it. The first DEM will determine the prevailing resolution."

From your example, I believe the 20 grid is higher res than the 25, so you may want to open your 20s first then the 25s.

Andrew

 

[Approach_Medium]

Thanks for that info. I don't think it really makes a difference whether I use 20 or 25 grid anyway. I would use 1/3Arc instead of 1Arc if I really wanted higher res. But for the large routes I am creating, 1Arc works fine.

FW