ISOM2017 wrote:The sizes of the overprinting symbols are given for the map scale 1:15 000. For larger map scales the symbols shall be enlarged proportionally (to 150% for 1:10 000, to 300% for 1:5000).
Larger scale maps should now be an enlargement of 1:15000 in every way including symbol and control circle size. I assume the intention is to make the map clearer to read and the scale easier to judge.
When coaching I'm starting to say the control circle is 75m across, but unfortunately that's not always been the case.
Correct use of enlarged circles might also discourage the trend for excessively short legs in Middle Distance and positioning controls too close together.
Personally I think the exception might be for junior courses where shorter legs or close controls are often necessary to suit course planning requirements and large overlapping circles can be confusing. See previous thread on British Schools from last year. But the event details should highlight any non ISOM2017 symbols.