ELVIS lidar data processed through OCAD 2018 DEM import
Mark Roberts recently reported
Just a note that I recently downloaded some lidar data from ELVIS and imported to OCAD 2018 and the results are spectacularly good. The vegetation height function depicts clearings and buildings perfectly:
Mark later remarked that lidar is becoming very readily available and the OCAD processing of lidar is so easy.
VIC lidar data processed through OCAD 2018 DEM import
Following Mark’s report I received ordered lidar data for a permanent orienteering course in Daylesford, VIC. Here in VIC we do not yet have free access, however on behalf of Orienteering Victoria I have established a protocol with DELWP for access to lidar data. As their paid orders take priority it takes some weeks to fulfill an order but the wait is certainly worthwhile.
Here are some matters that puzzled me or other mappers, but were eventually resolved. Take a browse to up your OCAD productivity.
Multiple OCAD instances
After an OCAD update to a new version (such as 11 to 12), do not be tempted to run both versions simultaneously on the one PC. The same temporary file names are used by both versions.
Characters inserting/deleting 1 or more places away from cursor?
I use cartographic fonts and a few fonts with slightly quirky styles. For many months while editing blocks of text on maps, I blamed my laptop for letters being inserted and deleted 1 or more places from the insertion point. After moving to a desktop PC and having the same issue, I thought to ask Mark Roberts who replied ‘ligatures’.
Ligatures are 2 or more letters combined into one character. ff, ae, fi, ffi, ft are often combined in a font that enables ligatures. See Wikipedia for more. OCAD recognise ligatures as a single character whereas your OS and you are seeing it as multiple. So if I write difficult in OCAD using a ligature font, OCAD thinks the cursor is 2 characters prior (the ffi being a single character). Note that ligatures in a block of text are cumulative in effect.
A 25 second video showing a normal insertion and then a ligature effected insertion. Deletions are similarly affected.
Solution 1 – do not use fonts with ligatures.
Solution 2 – once you understand there is a pattern, it is fairly easy to edit small blocks of text with ligatures.
A DEM elevation profile is back to front?
You may have merged many segments of track, or drawn a long curvy track, only to find the profile depicts the opposite direction of travel.
This is because the elevation profile function uses the direction in which the line was drawn (or traveled in the case of GPX tracks). Simply Object>Reverse Object Direction and redo the elevation profile. It is also a symbol on the menu that you might know better as the symbol to reverse the direction of fence tags.
On a stressful day, this is a calming 5 minute video. Though I’m not sure which is the more calming – the scenery or the voice.
Of all the paths you take in life, make sure a few of them are dirt. [John Muir]
The mapper of smaller scale maps such as trail maps, may be interested to know that three new colour ramps have been added to the hypsometric tinting choices in a coming OCAD update. One ramp allows choice of colours in up to 10 bands.
Brown – Yellow colour ramp
Brown (high elevation) – Yellow (low) offers a ramp similar to that of the Sustrans UK touring cycle maps. It is easy on the eye yet effective. The ramp in the image is at 50m intervals on a 1:100,000 scale map (and like our Spa Country Explorer trail maps, it is printed on Pretex).
Research shows that many users of hypsometric tinted maps think that colours have meaning for ground content as well as elevation. For example a tint that has green at the lowest level implies to those users that the green also represents forest or farmland. Therefore there has been effort to avoid colour ramps that could give rise to such confusion.
On the full map of the Brown – Yellow image, the cartographers have added a green overlay for specific forest sections. Those are not large areas so it does work well. (See Shaded Relief website below for an article Evaluating Cross Blended Hypsometric Tints)
Red – Yellow colour ramp
While Brown – Yellow colour ramp tends towards subtle, Red – Yellow is striking yet not glaring. The ramp used in the image is per 100m on part of an 80km trail trial map. The yellow is the Lerderderg Gorge (VIC).
I also trialled showing 50m contours on this 100m ramp. It may well be useful for less expert mountain bike riders who may be more conscious of elevation change when planning trips.
Colour yourself purple
The Greyscale Interval colour ramp is very useful addition. It produces a greyscale 10 segment ramp with each segment at your specified contour interval.
Using an image processing tool you can select each greyscale level in the resulting TIFF background file and change to a colour of your choosing.
After processing a segmented greyscale, I started up the ubiquitous IrfanView (free but well worth a donation). Sure enough, I found it had the ability to easily select a greyscale and change it to another colour. Below is the before and after image I generated using this process. Not a colour ramp you would use for real but you are welcome to add it to your art collection 🙂
For those interested in exploring hypsometric tinting specifically or shaded relief generally, then these two websites are good resources.
The ELVIS output format Esri Ascii Grid, can be imported directly into OCAD 12 via the Import Wizard in the DEM menu. So you not only have an easy way of obtaining the data, you also have an easy way of using it. (See my earlier post ELVIS rocks with LiDAR contours on the basics of using ELVIS).
ELVIS LiDAR vs state geospatial vector contours
For a small area of Anglesea used in 2015 for a mountain bike orienteering event, I downloaded ELVIS LiDAR and VicMap vector contours. Then overlaid them in OCAD.
The brown contours are VicMap 10m obtained via download of vector form via Shape file. 25m index contours were also obtained but do not appear in this fragment.
The other 3 colours are from ELVIS LiDAR data;
grey is 1m (shown only in second image)
green is 5m
purple is 25m index contour
At first glance there is a general consistency if we ignore the many minor indentations in the LiDAR lines that could be easily smoothed in OCAD.
However the 1m LiDAR does indicate the existence of two lower parts of gullies that are shown in the VicMap contours, albeit the eastern displaced. So maybe 1m contours could usefully inform the mapper at draft stage in some map areas.
This is similar to the result when smoothing in OCAD except that Karttapullauten has interpolated 2.5m contours (the dashed lines). Interestingly, this makes the progression of the above mentioned eastern gully much easier to observe.
When you download ELVIS data, it is the .asc file that OCAD DEM import wants,not the Shape file.
If you get nothing showing after import, then check the .asc file content. You can use any text editor to read it. In the header lines there is a value for NODATA. If the file is composed completely of that value then there is no LiDAR data for the area you selected. ELVIS now warns you if there is no data in the selected area.
When you are asked which co-ordinate set you wish to use, unless you have set up your OCAD file to match the location of the imported DEM data, then select the upper set which is that of the DEM data. Else the DEM data will likely be located far beyond the reach of your OCAD map area.
If you expect to frequently use LiDAR data, then importing into a special OCAD file can be a boon, It should be empty and have just essential symbols that don’t clash with standard symbols for when you import that OCAD file into your working file. Such a template is downloadable from the section immediately above.