Here is the next TransDEM patch. It will bring TransDEM to version 2.6.3. This time again, it's dedicated to DEM handling and the ever increasing variety of hi-res LIDAR-based terrain models. Visit my
website to download. The update is free for all TransDEM 2.6 users.
There is also a new version of WMS and map tile settings available for download. Of particular interest is the now nation-wide coverage, albeit partially incomplete, for the historic British O/S 25 inch product, the extraordinary large scale 1:2500 topographic map from a hundred years ago.
TransDEM 2.6.3 offers two new features (plus some bits and bobs):
- XYZ import now supports all geo coordinate systems known to TransDEM
- Most DEM file formats now allow multiple file selection for opening.
Particularly the second feature shall make life a lot easier when handling LIDAR data that is not in the XYZ form.
Both features have more in common than it seems at first glance. To accommodate them I partly redesigned and unified the workflow for reading DEMs.
The main difference between XYZ and other DEM formats is that for XYZ the total extent or the resolution of the DEM is not known until all data ave been read and processed, while for regular DEM that information is available a priori, either explicitly in meta data or implicitly from the file format convention (.i.e. .hgt).
XYZ import in TransDEM always offered multiple file selection, albeit limited to only a handful of files until TransDEM 2.6.2 last year. XYZ files are often rather small, so combining more than one into a single read operation is more efficient. But other DEM sources these days are also distributed as series of relatively small files, particularly high resolution LIDAR data. The new DEM reading workflow now allows TransDEM to support multiple selection for most regular DEM file formats as well.
And vice versa, the unified workflow lets XYZ benefit from the geo coordinate system handling for regular DEM file types, so XYZ is no longer limited to UTM or geographic WGS84 coordinates.
Regular and XYZ DEM read/write actions will remain as separate menu commands, as the concept of the two types is different and has not changed, see above.
Internally, the entire DEM read and write procedures for both regular and XYZ DEM types are now run in background worker threads, with intermediate input dialogue windows and message boxes synchronously brought forward to the main window thread. (In a graphical user interface environment, window handling itself is always single-threaded, independent of operating system and windows framework.) As a user you will notice the new background processing through a more responsive main window during DEM read and write operations, with additional progress bar activities and cancel options when reading multiple files.
The screenshots hereafter shall illustrate the usefulness of the new features with the help of terrain data from various parts of the United Kingdom.
We start with Northern Ireland. There is a 10m DEM avaibale from O/S NI Open Data, split into 293 individual files, grouped in packages of 50. The files are type .txt but are actually XYZ. TransDEM 2.6.3 has been enhanced to also accept .txt for XYZ. And these DEM files are in Irish National Grid (ING) coordinates which TransDEM 2.6.3 supports for XYZ.
![Image](https://img.transdem.de/albums/userpics/10001/nrthireland10m.jpg)
We visit Scotland next. There is 2m LIDAR available for selected areas via data.gov.uk. It's either ESRI ASCII grid or GeoTIFF. The GeoTIFFs may have a non-standard "Invalid" point marker. TransDEM 2.6.3 addresses this. The example here is "Neptune's Staircase" on the Caledonian Canal near Fort William, here with a overlay by the 25inch historic map.
![Image](https://img.transdem.de/albums/userpics/10001/fortwilliam.jpg)
Then we go to Wales. Again there is some 2m LIDAR, a bit hard to find on the Lle website. Files are ESRI ASCII grid, but coverage is limited again. It will often need complementation with some other DEM, typically O/S Terrain 50 as for this example in Porthmadog, with the historic 6inch map on top.
![Image](https://img.transdem.de/albums/userpics/10001/porthmadog1000.jpg)
For the last stage, the North of England and 1m LIDAR from the Environment Agency. ESRI ASCII grid file types, organized in O/S grid squares. The new TransDEM 2.6.3 multiple file selection is a real bonus here. We look at Burnley and the "Burnley Embankment", the Leeds & Liverpool Canal crossing the valley, an engineering marvel from the late 18th century. To the left is the present day motorway
![Image](https://img.transdem.de/albums/userpics/10001/burnley1m.jpg)
Burnley again, to the north of the "Embankment", with a 25 inch map overlay. The northern counties are a recent addition to the digitized 25 inch map series.
![Image](https://img.transdem.de/albums/userpics/10001/burnley1m2B25in.jpg)
Finally, a Burnley route in T:ANE. First here with ground textures and the modern 1:25,000 O/S map, acquired via Bing map tiles and an API key.
![Image](https://img.transdem.de/albums/userpics/10001/burnley-TANE-25k.jpg)
More examples from this route, now with 3D UTM tiles in 5m raster, carrying the 25 inch map:
![Image](https://img.transdem.de/albums/userpics/10001/burnley-TANE-25in01.jpg)
![Image](https://img.transdem.de/albums/userpics/10001/burnley-TANE-25in02.jpg)
![Image](https://img.transdem.de/albums/userpics/10001/burnley-TANE-25in03.jpg)
Have fun with TransDEM 2.6.3