Map scales (again!)

[Scott]

If we went that way, no need to increase the total number of maps printed, simply those who don't pre-enter before the maps are printed have their choice restricted to whatever is still available.

That would help, but I reckon the people-taking-two-maps-stuck-together problem, plus the minority who will be sufficiently confused to pick up the wrong scale map (or who simply change their mind in the start lane), will lead to some increase in the number of maps required - though probably not significant enough to be a real objection.

[greywolf]

Re BOC map scales: the two relevant BOF docs (Appendix H Mapping and Guideline D British Champs) aren't entirely clear or perfectly aligned - The former says "Whilst the main map scale is 1:15 000, a scale of 1:10 000 is recommended for M/W45 and above and for M/W16 and below.", whereas the latter says "If the Planner and Controller are in agreement then a 1:15,000 map may be enlarged to 1:10,000 for use by classes M/W45 and above and M/W14 and below. The enlargement should be such that the symbols are 150% of those on a 1:15000 map." However, while Appendix H says "A scale of 1:10,000 may be used where the area is of exceptional detail, subject to permission being obtained from the British Orienteering Map Group before the map is printed.", neither says anything about blowing 1:10,000 up to 1:7500. I agree with Awk, SJC etc that it's a logical step - but it needs formalising in a rewrite and alignment of the various guidelines. And I declare an interest: my eyesight is definitely fading, and I find blown - up maps a great help.

It occurs to me that if you have an area that requires A3 (i.e. 42 cm by 30 cm) for 1:10.000, then the same area at 1:7500 is going to need 53 by 40cm, which is getting on for A2, and thats a very big bit of paper, OR the courses for older age groups would have to be scrunched into a relatively small part of the area, which might in some cases be a bit of a constraint in producing a M45L course of c. 9.5 - 10k, which is what the guidelines suggest for BOC. But I can't find any rules for maximum paper size - how would we feel about A2 maps?

[Scott]

how would we feel about A2 maps?

That wouldn't be the only solution: you could print two halves of the area back-to-back (with sufficient overlap) or - if you were feeling particularly quaint - have a map exchange (if it worked at last year's JK, I don't see why it couldn't work at the British).

[oconor]

The International Specification for Orienteering Maps ISOM 2000 discusses dimensions in section 3.3.

This states that the minimum distance between two lines of the same colour should be 0.15mm for M21 maps.
This is also the width of fine lines.

Whilst not explicitly stated in ISOM 2000, I interpret all the guidance as follows:
The minimum seperation for two distinct features of the same colour, for younger age groups, on the printed map available to competitors should be at least 0.15mm. If M45/W45 and above use a larger scale map, I interpret the guidance as: For older age groups, the minimum seperation between two distinct features, on the printed map, should be at least 0.2mm.

1:10000 and 1:15000 are used for M21 because they allow a course of the appropriate length to be fitted onto an A4 map. However if the mapper wishs to display more intricate detail, or use a lower spec printer (especially for brown), then he should use a larger scale and bigger map, in order to retain the minimum seperation between features of 0.15mm. The difference in magnification between map scales is either 50% (1:15000 to 1:10000) or 33% (1:10000 to 1:7500), so for older age groups the minimum seperation between features should be at least 0.2mm.

Reviewing the Tankersley map, I can find no example where two features of the same colour are separated by less than 1.5x the width of a fine line, so this map meets the criteria as being suitable for an M45 competitor such as myself.

However when reviewing the Bouth 1:7500 M45S map, I can find in one 2x2cm square, more than ten examples where the seperation between two features of the same colour is less than the width of a fine line, making this map fail the standard for M21 let alone M45. I may have attached an image demonstrating this. (I hate to think what the 1:10000 M45L map was like!)

bouth2.jpg (88.38 KiB) Viewed 5240 times

The solution seems obvious, ISOM should include the statement:
The minimum seperation for two distinct features of the same colour, for younger age groups, on the printed map available to competitors should be at least 0.15mm, which is the width of a fine line. For age groups above 45 years, the minimum seperation between two distinct features, on the printed map, should be at least 0.2mm.

Rory

[oconor]

And one further point: Wikipedia defines normal 20/20 vision as being able to discriminate two points separated by one arc minute. If an orienteer holds his map 50 cm from his eyes (reasonnable) then this is equivalent to 0.15mm. So the requirement for features to be separated by 0.15mm is consistent with definitions of normal visual acuity.

And it makes issues of map scales partly irrelevant - because these will then depend on the size of course to be included and intricacy of features to be mapped - if you want more features then you have to have a bigger map or a tighter course or a better printer, but you cannot assume that competitors have suddenly developed the physiological ability to discriminate between features with a smaller separation.

Rory

[IanD]

I like Rory's idea of defining the map requirements in terms of resolution (distance between symbols) rather than scale.

With the proviso that something less than 20/20 vision should be required to read a map clearly. Orienteering is supposed to be a test of map interpretation, route choice and physical fitness - not of eyesight. Obviously we can't cater for everybody, but if average vision (in each age category) is required, we exclude nearly half the population.

[Roger]

I've been wanting 1:10,000 maps since my early days as an M21: even on a good forest road (Forest of Dean is the one I remember best), I just couldn't read the detail at the speed I wanted to run.

Now I'm 'entitled' to one (well, morally if not actually according to the rules), I understand the real reason. At an overcast summer-evening race last year, in a darkish bit of beech wood, I looked down and realised that I could not actually see what was on the map. Not even if I stood still and peered -- too close and I couldn't focus, too far away and the image resolution was too poor. I knew that there were some features there, but the map in and around the circle appeared to be uniformly light green. It was like suddenly being blinded or having a green sheet put over the map; it's no exaggeration to say that I was frightened.

Map legibility is not a trivial issue about saving a few seconds here and there; it's about being able to do the sport or not.

[greywolf]

you could print two halves of the area back-to-back (with sufficient overlap) or - if you were feeling particularly quaint - have a map exchange

The map exchange solves a slightly different problem, but i like the two halves of the area back to back idea. Not seen this done before, but guess it must have been.

ISOM 2000 ... section 3.3. ... states that the minimum distance between two lines of the same colour should be 0.15mm for M21 maps. I interpret all the guidance as follows: The minimum seperation for two distinct features of the same colour, for younger age groups, on the printed map available to competitors should be at least 0.15mm

I think your interpretation would be sensible, but all that ISOM says with regard to land form symbol separation (section 4.1) is that the symbol for small knoll (and elongated knoll) should not touch a contour line. It also says that elongated knolls should not overlap, but omits to say whether small knolls are allowed to overlap

But even by these limited rules, the map extract you show appears not to conform to ISOM 2000 in some places.

In a previous thread Redpossum said: "The IOF Map Commission is just beginning its revision of ISOM under the title ISOM 2010X. I'll make sure that our representative, Erik Peckett knows about these comments."

Perhaps we should ask that future specification includes minimum separations for land form point symbols: small knolls, pits, etc.

[Tatty]

Back to back maps has definitely been done down in the south. Never heard any adverse comments. Personally not sure how the over lap works. Are there some controls which are common on both maps?
Certainly doesn't seem to be a problem.

[Scott]

A couple of controls in common seems to be fairly standard (as at, for example, the Brown at the Sallowvallets CSC round), and I've always thought it works fine. Only time I've not been entirely happy with double-sided printing was at the 2007 Dartmoor Long-O, where a long route-choicey leg was split over the two sides of the map, which made planning your route a little more interesting (though aside from that it was an excellent event).

[RJ]

Splitting the course onto two maps can be done for two reasons.

One, is the large map that you don't want to print at A3, so you print two sections at A4 and put them back to back. Only really necessary to have the changeover control on both maps with enough common terrain either side of the leg to keep the runner in contact with the terrain as they turn over.

Two, where you have a small area and you are criss-crossing it several times. It helps to have the course split on two maps so that the red lines and control circles are more easily read. And also.... to keep the later part of the course out of sight. It makes the course overprint far less cluttered.

We've been doing it for years with considerable success.

[greywolf]

the large map that you don't want to print at A3, so you print two sections at A4 and put them back to back. Only really necessary to have the changeover control on both maps with enough common terrain either side of the leg to keep the runner in contact with the terrain as they turn over.

Presumably if the start and finish are on the same bit of the map you have two changeovers?

Anyone done A3 back to back?

[graeme]

Splitting the course onto two maps can be done for two reasons.

Clarity when criss-crossing is always very welcome.

I've never come across a map two sided because it was too big -
doesn't seem much different from folding in half. Unless it really is two areas
with a marked route between.

Two other things I have seen though ...
A map printed at 1:15,000 with a 1:7500 blow up of a really detailed section. (Great Falls, VA)
A long, thin map split in two on top and bottom of the paper. (Gullane Dunes)

..and also the "middle bit" on one side, start and finish on the other.

[RJ]

A map printed at 1:15,000 with a 1:7500 blow up of a really detailed section. (Great Falls, VA)

Yep... we did that for an Xmas fun event, with the centre section removed and printed on the back at increased scale. But rather than describe it here in detail ..... have a look at CompassSport next issue.... out in a couple of weeks!!

[NeilC]

And a few years ago SLOW managed to incorporate a 'normal' map, a micro-O map and, a sprint-O map into their OK Nuts regional event. I can't recall whether any course had all three but most had two.