This is not to claim that making orienteering maps is boring, as one dictionary suggests that a drone is “A person who does tedious or menial work; a drudge” ….. on the contrary, anyone who knows me will know that I find the work stimulating and rewarding, and certainly not menial. Indeed making orienteering maps is one of my passions in life, and another (there are more!) is the theory of flight Continue reading A Drone Goes Orienteering Mapping
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.
Following on from that is a 4 minute video of importing lidar data via the DEM import wizard. It is one of OCAD Inc’s video tutorials – DEM Wizard – contours
Users of OCAD 10 and 11 don’t have the wizard but should be able to interpret the wizard settings.
I created an OCAD template for importing the DEM data and creating the various contour styles. This file can then be imported into your OCAD map file without overwriting any existing brown contours. Head to my resources page for those.
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.
ELVIS is Geoscience Australia’s new elevation information system. It is free, licenced under Creative Commons and makes public LiDAR data very accessible. Thank you to Russell Rigby, mapping convenor ONSW who made me aware of ELVIS. The LiDAR data available is;
SRTM-derived 1 Second Digital Elevation Models Version 1.0
DEM SRTM 1 Second Hydrologically Enforced
5 metre Digital Elevation Model (DEM) – this delivers 1m, 5m, 25m contours
I downloaded 5m DEM data covering part of the 2015 Anglesea mtbo map, imported contours into OCAD and overlaid those on the OCAD map file of 5m contours. The correspondence was very close which is a tribute to mapper John Sutcliffe as much as to the ELVIS data.
The 5m resolution coverage, which provides down to 1m contours, is fairly thin. These surveys cover Australia’s populated coastal zone; floodplain surveys within the Murray Darling Basin, and some parts of major and minor population centres.
Maybe we will see more sand dune coastal area maps akin to those near Hobart, Auckland, Levin and Invercargill. And perhaps street and park-O where more detailed contours are desired.
Ease of use
The website isn’t yet the friendliest until you get to know it and then it does work well. Here are tips based on my learning;
Symbols of available datasets
Selecting a right arrowhead symbol provides a synopsis of that data type.
Selecting a download arrow symbol takes you to the selection of data coverage for your project.
Selecting the globe symbol, (red when selected) shows on the map at left, the available coverage for that data.
Selecting the ‘eye’ symbol (orange when selected) show the extent of that data coverage.
Note the latter two symbols act like check boxes, not radio buttons.
Selecting a 5m dataset
At time of writing, selecting the name of any state 5m dataset gives you identical national information. It also has links at right (when selected) to state mosaic downloads – these are of no relevance to OCAD use.
Selecting the download icon frames the 5 metre DEM coverage area for that state.
Download of data
Whichever dataset you choose, the method of selecting data is the same. The download wizard is easy to follow.
For Output Format, select Esri ASCII Grid for OCAD import. The file will be a .asc type file.
For Coordinate system, select GDA94 for OCAD import.
A generic LiDAR workflow in OCAD orienteering mapping
Orienteering isn’t mentioned amongst the 17 industry uses of Light detection and ranging (LIDaR) that Wikipedia covers. Yet LiDAR is being adopted increasingly for our mapping. It offers a reduction in effort, sometimes significant, in both cartography and field work. Bendigo Orienteering Club, VIC was an early adopter of LIDaR and some of their experience will be covered in a forthcoming article.
So what is involved in our using LiDAR? The following 5 step generic workflow from OCAD AG gives you an insight.
1. Import LiDAR data
LAS (interchange format of 3 dimensional point cloud data)
XYX (RAW data ASCII)
ASCII (ESRI ASCII Grid and ESRI Grid XYZ)
SRMT (Shuttle Radar Topography Mission)
LAS is the preferred format if available as it is efficient and non-proprietary.
DTM and DSM
Separate Digital Elevation Model (DEM) data sets can be derived from LAS. These data sets are the Digital Terrain Model (DTM) and Digital Surface Model (DSM). These allow calculation of vegetation height.
Different parts of DEM data can be merged in OCAD 11.
2. Derive contour lines
Contour lines can be derived at any interval. Assign LiDAR data directly to symbols of index contour line, normal contour line or form line.
The option split in tiles, can save time in deriving contour lines.
3. Derive hill shading
Maybe not for orienteering? However, samples I have seen of relief shading at high resolution, can reveal ditches, erosion gullies and small depressions.
This functionality is likely to be very useful for trail maps.
4. Vegetation height map
This process can not only show vegetation boundaries but also vegetation stages. The latter can indicate the likelihood of runnability and even visibility. For example short, and therefore young, pines are likely to have low runnability and maybe low visibility. Is this useful in preparing for field survey? Maybe we will find out from Bendigo’s experience.
A practical use
A recent development in NSW has enabled detection of species using LiDAR mapping. This is to sufficient accuracy that it is saving considerable field hours in forest management including assessing fire risk from season to season.
5. Derive slopes and cliffs
A slope map can be derived. Cliffs can also be derived according to steepness. For example any slope greater than 60º might be designated as a cliff. The field mapper would then determine if it does rate as a cliff and if so, is it rock or earth. Nicely, the location is already fixed.