What is of interest is what lies behind the requirement that the enlargement from 1:15000 to 1:10000 should not include any extra detail. The follow-up is that many mappers are now saying that the survey scale should be 1:7500. For reasons I will give shortly I have invariably used 1:10000 scale to survey and would hope to be allowed to continue, as I see no reason to make a change.
Not many will know that the background to the concerns from IOF mainly arose out of the Graythwaite map in the Lake District and its use for an international event last year. As those who ran on the area in this year's British Championships will know, the map is at 1:10000 scale with most symbols at 150% but some drawn smaller. Because of the area's technical detail, the BOF appointed mapper had said that the area could not be shown clearly at 1:15000 scale. I understand that some members of IOF strongly disagreed and stated that if it could not be shown at 1:15000 the area was unsuitable for elite orienteers. Hence, I understand, the insistence in the future on the 1:15000 scale. Where that leaves Graythwaite I am not sure.
Returning to my concern about survey scale, I believe that with computer cartography one should be allowed to survey at any scale provided the techniques used give the required accuracy and that features can be clearly drawn. In my opinion survey scale should not be mandatory and I consider that in East Anglia 1:10000 is an appropriate scale for ground surveying.
For the main primary line traverses, as most know, I survey using a wheel. Generally the base map I use is either a previous O map or an OS base map: both are usually at 1:10000 scale. At this scale I find that I can quickly convert wheel measurements into millimetres by dividing by ten. The wheel is a far more accurate measure than pacing and it is almost impossible to lose one's place because all the readings are recorded on the tachometer. It is then much easier to divide my measurements by 10 rather than by 7.5 which is the conversion factor one would have to use for a 1:7500 survey scale.
For the secondary traverses within the primary traverse I sometimes use a wheel but usually pace, since these are only short distances. For me, surveying at 1:10000 scale, 6 double paces are equivalent to 1mm on the map and over short distances I can usually convert paces into plotting length in my head. However I would have to use a pace scale for the 4.5 double paces per millimetre I would need at 1:7500 scale. If you had ever had to explain this calculation to first time mappers on a beginner mapping course you would appreciate the difficulties it causes. I am all for making things simple and uncomplicated and hence I hope to continue surveying at 1:10000 scale.
Peter Leverington (NOR)