TransDEM Forum

Hi folks.

Rather new to this and am having an issue to which I have not been able to find a solution. I don't know if this is a TransDEM, GDAL or Microsoft situation.
Any help will be greatly appreciated.

I down load a map from USGS as a geo.tif.
I try to open it in TransDEM 'OPEN DEM'.

I get "error reading file"
"tiff/geotiff:jpg compression support not configured"

Thanks in advance for any and all help you may offer.

Chris

G'day csabie,

Chris, the cause of the error is somewhat explained by the wording of the error. However, it may not be obvious unless you are aware that there is only one 'kind' of "zipped" DEM file that TransDEM can open. The only DEM file type that TransDEM can open from the *.zip file is one with the extension *.hgt - All other *.zip files MUST be extracted prior to any attempt to open their "compressed" files in TransDEM. If I recall correctly, all files downloaded from the USGS are in *.zip format (irrespective of the format of the file selected from the search options)...

Jerker {:)}

What kind of geo data is this, a DEM or a raster map? I would guess a raster map, as jpeg wouldn't make much sense for a DEM, because it's a lossy compression.

TransDEM will treat TIFF files very differently for both cases, but may also fail. TIFF is a container format and has many options to encode the data within. TransDEM supports the most common encodings but will surely reach its limits when it comes to certain more exotic variants. Hence I am not sure whether TransDEM can handle jpeg inside TIFF for a raster map.

The process that I tried is this:
I downloaded a file from the USGS map site. "http://ngmdb.usgs.gov/maps/TopoView"
I search for a topomap of an area that I want. "It is a geo.tif.zip file"
I unzip the file. There are 4 files extracted. There is a geo.tfw, geo.tif, geo.tif.prj, and a geo.tif.xml file.
In TransDEM, I choose "Open DEM" and it shows the geo.tif file.
I select that file and press open, and receive the above described error.

Sorry but I am not that well versed in the content of certain map files as I am a rather newbee in this.
I do appreciate the input.

So, this is a raster map then. In TransDEM, it must be opened as such. But TransDEM will still fail because it does not support the rather exotic jpeg compression inside a TIFF container. Don't worry, the USGS has a certain reputation for choosing weird file formats. A couple of years ago, GeoPDF became the latest hype, after they'd just retired GeoTIFF proper. At that time they also started with the invaluable historic map series, and GeoPDF was the only format they presented the data.

That made me start investigating GeoPDF for TransDEM, the most complex data format I had come across so far, far too complex to implement it myself. GDAL, at least some specific builds of the library, provided the solution eventually. And that's where we stand today. Download the map in GeoPDF format. Make sure you have GDAL installed - see the TransDEM manual for the download link - and open as raster map. Georeferencing is included in the file - hence GeoPDF - and TransDEM will detect and read the meta data for it.

If you haven't used any of those geo data files before, I urgently recommend to read the TransDEM main manual, chapter "Georeferencing of Raster Maps", from page 40 in version 2.6. It also tells you about GeoPDF processing.

USGS GeoPDFs have a nice little extra feature: the "neat-line". It allows TransDEM to automatically crop the map collar (aka margins), and you get rid of all the white space and the legend.

Thank you geophil.

I will follow what you have advised and much appreciate the info.

Chris