What detail can be left off the map?

[NeilC]

It is clear - the mast stays on. From what I read the power lines must also stay (the area has some). I am pretty sure that I have run at major events where these were missing - does that mean wrong decisions were previously made or did the rules change?

Read ISOM carefully. Decisions have to be made as to what features to leave off the map in order to make it legible (but without significantly affecting its accuracy). Large pylons and powerlines on open fell are usually very significant features. Small powerlines in forests are easily missed on the ground and can confuse the runner by being easily confused with fences, magnetic north lines etc on a crowded map. And as ryeland of doom mentioned often run parallel to more obvious features. I'm not aware of mappers leaving powerlines off in order to make navigation more difficult - just to make the map more legible.

[Clive Coles]

i think it is really a map clarity issue together with that of consistency.

Where powerlines cut through the forest the vegetation beneath the line is often different to that of the forest , ( typically scrub or rough open).

The change of vegetation is usually shown by a distinct vegetation boundary marking the switch between forest and scrub/rough open.

If therfore you attempt to show a powerline between two distinct vegetation boundaries the map becomes cluttered. In these circumstances I would find it clearer if the powerlines themselves to be left off the map. I could argue we should be mapping what we run through ~ what is up in the air is of no relevence to a ground based sport.

i would however expect the base of the pylons to be mapped. These are ground features and could be used as a useful control site for a junior course such as an orange.

Where there are telephone lines running through a forest I would not expect either the phone line or poles to be mapped. Again these lines usually follow other mapped features such a paths or rides.

The important thing is that you are consistant across the map and that, if you take a non ISOM based decision, you state what features are not mapped on the map itself.

[70plus]

There has always been a temptation to leave prominent features off a map to make a competition more technical. The problem may be that if the area is that technical, a prominent feature may be the only thing that will help a lost competitor to relocate. For juniors especially, that must be considered.

I can support a case for leaving off power lines as they are not ground features (the poles are only more trees, which we don't usually map), and on a busy map can be misread as fences. But a large tower is certainly a ground feature and IMHO cannot logically be left off.

I recall a suggestion MANY years ago to omit major rides from a map of Clocaenog Forest (!!). As rides were about the only means of determining one's position, that would have made for a very interesting competition.

[Red Adder]

When I started 35 + years ago rides were generally mapped. In EA this is now rarely the case - I my case as I find the FC often cut them only 10-15 m apart and so they tend to add clutter but do not give many interesting control sites. I do often map them in the survey as they can be useful in position point features.

[70plus]

Red Adder - I think you are referring to rides, while I was probably describing what you would call firebreaks, which don't occur at 30-metre intervals. They were also the usually preferred route 'across country' in Clocaenog Forest. [ we recently reconnoitred that forest in case it still had potential. Even the 'rides' in the part I looked at were overgrown. What a pity forestry habits have changed so much in recent decades ]

[AndyO]

I expect a map to accurately represent the terrain in the eyes of the mapper, as the ISOM spec requires. I don't see any reason to omit power lines or masts other than for clarity on the map, but that should be noted clearly in event details and at registration. There's nothing wrong with leaving out detail (or switching off black features, or contour-only maps) for training purposes, but for events at any level you must expect the map to be accurate and up to date.