Some observations on mapping following the third NZ Championship in MTBO.
Rob Crawford who made the maps for the 3rd NZ MTBO Championship read the IOF mapping specifications with fresh eyes. He discovered that the colour white as used in foot-orienteering for easily passable forest is allowed. Previous NZ maps have generally used light green.
The actual wording is as follows. "The representation of vegetation is of importance to the competitor only for navigational purposes, not for route choices. If for example the forest is dense on one side of the path and sparse on the other, this presents navigation and positioning information. It is not necessary to grade the forest for "speed" purposes unlike maps for foot-orienteering, only for visibility. In order to meet the demands for highest possible legibility, the 30% green colour as used for (symbol) 406 Forest slow running has been judged optimal."
This suggests that the perfect MTBO map would have a mixture of white and light green, and the specification also lists the four different shades of yellow for open or semi-open land, plus three combinations of yellow and other colours for orchards, vineyards and cultivated land.
Some of these distinctions would seem to be rather arcane, and less important than trying to get international consistency for the track ridability values. Likewise distinguishing forest density might not be a top priority at this stage of the sport. There isn't any guidance in the specification as to what the dividing line should be between "dense" and "sparse" forest.
In the short term there doesn't seem to be anything wrong with using EITHER white or light green for ALL the forest on a map. In favour of white is that other detail shows up better through it. In favour of green is that it is more intuitive for those who haven't come from a foot-orienteering background.
Now for something more useful: the use of a small purple bar across a track to indicate a single obstacle which requires dismounting. As opposed to a length of track which is not ridable. Examples of single obstacles would be fallen trees and closed gates. Hint for cartographers, you can easily make this symbol by changing the colour of the "bridge" symbol 512 to purple. This hint is not in the specifications, but as it was used in the World Champs there is some authority for it.