Editors Note: the following article is from John's August 2011 Controllers Corner.  I think we are all pretty good at getting this right these days but thought it worth revisiting anyway.

Our sport is an incredibly precise one: precise maps, precise course planning, precise placement of controls, and the need to describe these placements as precisely as possible. Hopefully this is followed up by the competitors with their precise navigation!
Preparing control descriptions is a somewhat subjective process, although there are guidelines and regulations for us to follow. But the course planner has to provide an interpretation that will be accurate in assisting the competitor to locate the control.

From time to time I come across some descriptions that are not as accurate as they should be – especially in describing the actual feature. There can be a bit of a trap here because we look at the control feature in the terrain and are tempted to describe it according to how we see the feature. For example, on our Trevallyn map we have heaps of horse jumps on the map. Some might be wooden; some stone; some earth banks. So the temptation might be to put in a control description as a stone wall. But, the map has used a special symbol for a man-made object for all the horse jumps. The feature does not appear on the map as a stone wall. The control description needs to match what is on the map rather than what you see out there in the terrain. The correct description should be a man-made object.
Often when we are course setting in complex terrain we might not feel all that comfortable with how the mapper might have interpreted various rock detail, for example. The map might have boulder marked, but to the course planner it might look more like a boulder group (especially in dolerite rock detail). But the control description should refer to the boulder. The control description has to describe the feature in accordance with the way it has been mapped.
OK, so what do the course planner and controller do about it when they feel especially unhappy about how feature is mapped and how they want to describe it?
One option is to move the control site away from the area of confusion. This is a pretty safe and practical option, providing it does not damage the integrity of the course planning at and around that point.
A second option is to provide advice to competitors that they might experience some confusion. For example, in the granite reas of our St Helens maps, boulders are shown as the usual black dots (of various sizes). The control description will identify a boulder. That is unless it is a lump of rock that is sitting IN the ground rather than ON it, in which case it has been mapped as a brown earth knoll (i.e. a contour feature). Consequently, no matter how much it looks like a lump of granite, the control description must describe what is on the map – i.e. the earth knoll. For major events on these maps, the event notes generally make reference to this aspect of the mapping (and consequently the control descriptions).
There is a third option, and this one is sometimes exercised in regard to a major map on a new area (or on a newly revised map for the event). Here the planner and controller, if they feel uncomfortable with how feature is mapped, can liaise with the mapper who will then revisit the site and review the mapping. Ultimately though, the organisers must accept what the mapper has drawn.
A related aspect of this is that maps are living documents, and while contours and rock details will remain unchanged, fences, tracks, man-made object and vegetation can all change and maps need to be updated. Thanks to OCAD this is now a relatively easy task and is something an event organiser should take up with their club mapping officer if a map requires changes.
If you want to follow up more on the whole area of control descriptions, you can access the IOF detailed guidelines on the following web site:
https://orienteering.sport/iof/rules/control-descriptions