Creating a reference system

Every map needs to be congruent with a reference system. This will generally be a Universal Transverse Mercator (UTM) projection. There are three easy methods of starting the map with this sorted.

• Use the New Map Wizard on recent versions of OCAD. This is foolproof.
• Find the area of interest using Open Street Map. Export an OSM file from Open Street Map. Import the OSM file into OCAD or Open Street Map and accept the coordinate system it suggests.
• Process some lidar data to create a georeferenced image such as a slope file. Open this as a background map in OCAD or OOM and the correct coordinate system will be established.
• Greg Wilson also describes a manual system for georeferencing an old map in Open Orienteering Mapper. 

Creating the contours and other mappable features

Every mapper would like to start the mapping task with a high-quality base map. A high-quality base map will mean less time spent in the field and a more accurate final map.

• Lidar data with a reasonable point density will provide a highly accurate and detailed base map showing detailed contours, vegetation density, cliffs, water courses and point features such as pits. 
• Analog photogrammetry was once the base map standard. Today the analog photogrammetry machines have gone to the scrap heap. The last of the Chris Wilmott photogrammetry has been used. However anyone updating an old map will be using photogrammetry derived contours. In a landscape with meaningful elevation differences, these will contain some geographic distortions. 
• The base map of last resort is based upon coarse Digital Elevation Model (DEM) data. This data set may contain a data point every 10 metres. Clearly this will produce very simplified contours. However, when coupled with the use of an accurate GPS, a mapper can still produce a quality map. The best evidence of this is the Rowdy Flat map produced by Alex Tarr using 10 metre DEM contours and a GPS created basemap showing line and point features. 
• Modern digital photogrammetry is a potential tool for areas with limited tree cover. This may provide a solution for small sprint map areas, but these are likely to be in urban locations where lidar data is available.

What is Lidar data and where to get it

A short explanation of lidar technology is here.

Lidar data was first used for orienteering mapping in Australia as part of the 2012 Easter carnival in Bendigo (The maps La Trobe Bendigo, Yorkshire Hill, and Crusoe).

ELVIS: The ELVIS (ELeVation Information System) web site hosted by GeoScience Australia is a portal that is increasingly being used by various jurisdictions to store lidar data. The site seems to have complete coverage of NSW, near full coverage of Tasmania, sparse patchy coverage of Victoria and Queensland and coastal and river coverage for South Australia. West Australia misses out. The lidar quality is variable, ranging from high density in more recent uploads to low density (1 point per metre) in parts of Tasmania. If there is no lidar on the site for your area, there may be some DEM data, though this is often very coarse.

Grey lidar data:  Not all publicly held lidar data has been loaded onto the ELVIS site. The extent of grey data varies between states and access will vary according to the state. Approach your state Mapping Coordinator for further details.

Commissioning lidar: Failing these sources, your organization may decide to commission a lidar flight.

A guide to commissioning lidar by Noel Schoknecht. 

Other useful data sets

Each state has a cadastral boundary web site.

• NSW – SIX Maps 
• Victoria – MapShareVic 
• Queensland – Web map service 
• South Australia – SAPPA 
• West Australia – Map Viewer Plus 
• Tasmania – ListMap 
• ACT – ActiMap 
• Northern Territory – NT Atlas 

Some of these sites also provide aerial photography. There are commercial providers of high resolution imagery. Basic georeferenced imagery can be downloaded from Google Maps using OCAD.

Processing lidar data

Lidar data is generally used to produce contours, slope and terrain images and a vegetation map.

Today there are two main and one uncommon approach to the creation of a base map using lidar data.

• Using free software packages to process lidar (OL Laser, Kartapullautin and the Relief Visualisation Toolkit)
• Using the lidar processing capabilities of OCAD18 or OCAD22
• Less commonly, using command line programming of the extensive LasTools suite.

It’s not uncommon to mix and match the three options. Below are some links to useful instructional resources.

• Greg Wilson of Canberra has written a comprehensive description of his workflow to create base maps using free software tools. 
• Hamish Mackie instructions on making a base map with Open Orienteering Mapper. 
• OCAD provides a Wiki that explains use of OCAD to process lidar and DEMs. You can use XML code with OCAD to process large amounts of data. This is explained in a blog post.
• Greg Wilson’s blog provides a useful primer on the use of Kartapullautin 
• David George’s guide to producing base maps from lidar data. 
• Terj Matheson (from Norway) has developed a command pipeline to generate base maps from lidar using LasTools. Here is his guide. 
• Manu Jurado introduces Sky View Factor and the Relief Visualisation toolkit. 
• Off the shelf lidar will normally be processed to remove buildings from the ground layer. This also removes many rock outcrops and mounds. On some terrains (granite and mining) it may pay to reprocess the ground layer using the LasTools routine Lasground new. This is discussed here with before and after examples. 

Clearly there are multiple approaches to base map generation using lidar data. The nature of the terrain will influence the choice of tools. Here are some examples reported by Australian mappers:

• Evaluation of lidar tools for mining terrain after the first Australian use of lidar for orienteering mapping in 2012.  Note that some of the software capabilities have changed since this was produced.
• Alex Tarr’s evaluation of lidar base maps (when not using a tablet or GPS]. 
• Lidar workflow in WA granite terrain in 2018. 
• Report on lidar use in SA terrains in 2018. 
• Report on lidar use to prepare base maps in Tasmania. 

Analog Photogrammetry Base Maps

Analog photogrammetry such as this was once the gold standard for orienteering base maps.

The analog photogrammetry machines are now museum pieces. The transparency film used to create the photographs required for these machines has not been manufactured for some years. It is highly unlikely any orienteer will be using base maps such as these today. However, some mappers may find themselves updating older maps without supporting lidar data. In this case, they are still working with photogrammetric contours that have been field worked without GPS assistance.

A comparison of photogrammetrically derived contours and quality lidar contours is shown below. The purple lines are 2.5 metre lidar contours. The brown are the old 5 metre contours derived from analog photogrammetry. The two highlighted areas demonstrate geographic misplacement and what may be errors in the old data. Elsewhere a discerning eye can detect areas where the old contour lines exaggerate the features, and areas where they diminish the features shown on lidar.

Improving these contours, even with GPS assistance, will often be labour intensive and require an approach described in the section on use of coarse DEM data. If you can access lidar data, it will be easier to map again from the lidar base rather than adjust the old map. If you cannot access lidar data, and attempt to update the map using GPS assistance, there will be areas where contours will need to be significantly reworked.

Coarse DEM Base Maps

In Victoria there is full state coverage with a 10 metre DEM. The OCAD DEM Import wizard can create contours based upon this data. The resulting contours are very broad with no fine detail. That detail needs to be created by the mapper. A GPS enabled tablet is invaluable in this task. In some landscapes the contours will only need adjusting by eye. In more complex contour landscapes, the mapper may need to walk the line of selected levels and use the GPS trace on the table to create a more accurate draft contour. Finally, this draft will need to be adjusted by eye to represent what the orienteer will perceive whilst running.

The comparison of DEM and final contours is shown in two examples below. In the first example, there is significant difference between the two, indicating the extent of extra work dictated using a poor base map. In the second example there is less variation, indicating either the terrain is of poor quality, or it has many point features not shown in this base map.

High variance between DEM and final contours

Low variance between DEM and final contours