Just to add to the conversation - I suggest it’s worth thinking about the specific separate functions of the controls and maps.
At the core of GPS-based orienteering is the use of the GPS in the device to match locations in the list of controls represented as geo-coordinates. (typically Lat/Lng). It’s good to keep the required approach distance to a control to the minimum that can be practically achieved, and so getting the controls at accurate Lats/Lngs is critical. I suggest a good way to do this is to drop pins on features that can be identified in satellite imagery. Everything has inherent errors, but this works pretty well in practice. LiDAR can be good if you have it. Determining control sites using an Orienteering Map as the background is too inaccurate… move the control 1mm on a 1:10000 map and it’s moved 10m on the ground. Also, the rules of orienteering mapping mean that sometimes features are deliberately moved from their “correct” Lat/Lng to achieve separation between symbols etc.
How accurate the Orienteering Map is in a GPS-based Orienteering App, doesn’t affect the reliability of punching virtual controls. So, the map accuracy question is one of what purpose is being achieved by having the map in the App. … to replace the paper map (probably not), to display tracks in results, live tracking, etc.
One workflow that works pretty well for routine Club Street-O type events using GPS-based orienteering is:
- Setup the map – either as an export from oomap.co.uk
(converted to KMZ) or OCAD export in KMZ
- Have the setter drop pins on features in Google Earth (GE). The Orienteering Map (KMZ) can be used as an overlay in GE, but ultimately the controls should be accurately placed on features identifiable in the satellite imagery (producing a KML file). GE is free and most people can get the hang of it, so setting can easily be disseminated to a larger group.
- When publishing the event, use a system that auto-generates the PurplePen file for printing. This is important to be sure that the controls in the App are the same as the ones on paper. (Having two independent versions of the event ultimately leads to problems.)
GPS accuracy is getting even better, especially where devices use multiple satellite systems. This is partly being driven by the needs of self-driving cars, auto-delivery via drones etc… so the future looks interesting!