TransDEM Forum

The LRIS portal (see here) has made available their 25 m DEMs. The product is called NZDEM.

They were created by Landcare Research from the 20m contour lines of the LINZ 1:50,000 maps. (Read more about the making of these DEMs here: Development of a High Resolution Digital Elevation Model for New Zealand).

I had a closer look at these DEMs and for this I picked the Taranaki Region on the North Island, famous for its (quiescent) volcano. I will compare 25m NZDEM (right) to standard SRTM 3 arc sec (left). Click on the images for full size.

First the entire northern half of the peninsula. LINZ Topo50 maps on top of the DEM. Not much difference at this scale.


Now we are zooming in. The lower Pouakai Range to the north of the main peak. See how closely the DEM-derived contour lines fit to those the topo map for NZDEM.


Next is Mt. Taranaki or Mt. Egmont itself with its spectacular conical shape. Again, compare the 100m DEM contour lines, both DEM-derived and on the map.


The last DEM image is taken to the north-east of the volcano, the Waitara river bed, this time with the railway vector layer added, the New Plymouth Line and the branch to Waitara.



Finally, the real thing, from a more earthly perspective. Photo taken a good decade ago, during the "Bluff 2000" tour.

Sorry for bringing up an old thread but i'm having an issue with the data in question -

Tranzdem just refuses to load it. I download NZTM projection and "ASCII" Grid format, set Tranzdem to NZTM also, and it just sits there - no error message or anything. Was there anything else you did before importing it?

Another idea would be to convert it to a different format - can anyone suggest a good program that will both open .asc and spit it out in a tranzdem acceptable format?

I would love to be able to use this data as it looks superb

Any help on the subject would be greatly appreciated.

Which version of TransDEM are you using? You may need a fairly recent one for support of national coordinate systems with ESRI Grid format (*.asc).

2.0 - Probably where the problem lies. However it does list .asc as an acceptable format... odd.

The ASCII Grid format as originally defined by ESRI required geographic coordinates (lat/long), based on the WGS84 ellipsoid / geodetic datum. Over the years, ESRI grid started to be used with projected coordinate systems as well. I added support in TransDEM for projected coordinate systems in TransDEM 2.1, after British Ordnance Survey DEMs in OSGB36 coordinates were made available to the general public last year. The new New Zealand 25m DEMs in NZTM coordinates benefit from this as well.