Register | Login
Attackpoint - performance and training tools for orienteering athletes

Discussion: Boulders 1M high, or higher

in: Orienteering; General

Apr 29, 2017 11:22 PM # 
ISOM 2017 specifies a boulder as:

204 Boulder
A distinct boulder (should be higher than 1 m), which is immediately identifiable on the ground.

(For what it's worth, ISOM 2000 said: A small distinct boulder (minimum height 1 m). Every boulder marked on the map should be immediately identifiable on the ground.)

From this definition, a tiny shard of rock 1.05m high can be a boulder if it's immediately identifiable on the ground, but a 3m wide slab of rock 80cm high shouldn't be (but the spec doesn't say mustn't be). Even if both are immediately identifiable, the latter is generally much more obvious, even dominant.

What do mappers and orienteers prefer in this situation, and all the gradations in between? Should a boulder be mapped primarily by height, or by obviousness (or by volume)? The former is a relatively objective standard, but can lead to a tiny volume of rock being mapped and the huge lump next to it not. Obviousness makes some intuitive sense, but is hugely subjective, and at some point one needs to draw the line when a rock is wide but not very high (40cm? 50cm? 60cm?). Volume is both relatively objective and related loosely to obviousness, but has the same quandary about height (is a cubic meter of rock 45cm high a boulder?). Or some combination...minimum 1m high and minimum 1 cubic meter of rock.

Apr 30, 2017 12:52 AM # 
I had trouble with this definition when mapping an old stone quarry. There was pieces of rock in the spoils heaps that were over 1m high, 1m wide, but only 10cm deep - basically a small slab stood up on edge. I left them off for two reasons - they weren't natural, so the runner wouldn't expect what they saw; and because the damn thing might tip over at any point. :)

I tend to favour "distinct" over the strict 1m limit. I like that the new standard says "should" rather than "must", as it gives you leeway on both height and distinctiveness.
Apr 30, 2017 3:08 AM # 
I think we should use Potter Stewart's definition of pornography.
Apr 30, 2017 7:15 PM # 
It doesn't matter how big it is as long as it's useful for participants.
Apr 30, 2017 7:30 PM # 
Wouldn't 3m wide slab of rock 80cm high" ressemble to a knoll? A Scandinavian classic: a boulder is a rock standing on the ground, standing out of it. A knoll may be a rock (partially) "blended" with the ground. The material is not essential, the features are.
Apr 30, 2017 7:33 PM # 
Minimum surface area for boulder and cliff: π m2
May 1, 2017 12:39 AM # 
Is that 'building pass through metres squared'?
May 1, 2017 4:53 AM # 
π is pi, 3.14 m2. Less tricky to remember.
May 1, 2017 5:25 AM # 
A long time ago I was at a mapping workshop and one of the best pieces of advise I got was to base your decision about what (and whether) to map based on your 'first impression'; rationale basically being this simulates the orienteer at speed entering the area. If you have to spend 15 minutes scratching our head and wondering about it, chances are it shouldn't be on. Imagine yourself as the orienteer running - what stands out, what do you notice? Then of course take all the time you need to map it correctly (shape, location etc.), but the actual first decision about it should be made very quickly.
May 1, 2017 6:04 AM # 
If I spend 15 minutes scratching my head over one feature, it generally means I'm hungry and my brain has gone on strike. :)
May 1, 2017 7:36 AM # 
Less tricky to remember.

My name is easy to remember.

If you have to draw the shape of a feature, chances are it's big enough to warrant drawing. A dot on the other hand...
May 1, 2017 2:57 PM # 
Mapping only rock pillars, and not dot boulders, would mean several pillars mapped, but leave lots of two and three meter boulders unmapped, not to speak of numerous one meter boulders. However the idea of only mapping boulders a minimum of two meters high is starting to grow on me. The bouldery areas might actually be much more useful, as mapping every one meter boulder makes for ridges too full of boulders for the rock to be terribly useful. (The boulders are mostly not so close together that one needs the boulder field symbol, but when I look at the map, I give up much hope of using them for controls or even navigation.). Does this approach sound too extreme? Alternatively, I could use a 1.5m minimum, maybe only doubling or tripling the number of boulders from a two meter minimum. If I do this, should I use a similar minimum for rock faces and cliffs, just to be consistent? Thoughts, experience with such?
May 1, 2017 3:27 PM # 
I'm not a fan of mapping 100 distinct boulders in a small area. As mentioned, it simply is not useful for navigation. At that point, I'd probably just switch to the large boulder symbol and map the rest as a boulder field.

Back to the original question, this comes up a lot in Missouri. We have many "boulders" that are well under a meter high, but might have a very large surface area (5x10m is not uncommon). I map such areas a bare rock. If it's too small for the grey dot to be noticeable on the map (such as a 2x2m slab), then it's a tougher call. I'll usually go ahead and use the boulder symbol if it's not surrounded by much other rock. Otherwise, I'll just leave it off.
May 2, 2017 12:02 PM # 
Terje Mathisen:
The main problem with borderline boulders in Norway is related to hillside locations:

Many boulders can be immediately obvious as such from the down side, but still look like a 30 cm hump of moss from the top side. Do you map them or not?

I have been tempted to remove all the moss if/when I need a control symbol in the area, i.e. making it much more obvious.
May 2, 2017 12:28 PM # 
Here's a fun contextual routegadget and a picture

Some people thought this was great and others thought there were too many rocks. The runners in the picture are doing leg 22-23 on course 1.
May 2, 2017 12:57 PM # 
I measure boulders sidehill. This means that the mapped ones are higher than a meter on the downhill side, and often shorter than a meter on the uphill side. It seems like the best compromise, but it does leave the case where the boulder is extremely obvious from downhill and not much so at all from uphill.

What was the minimum size boulder mapped there, roar?
May 2, 2017 2:07 PM # 
I'm not really sure. The information just said: "All areas are strewn with large boulders, up to 5m high. Not all boulders are marked."
May 2, 2017 3:00 PM # 
Boulder and cliff mapping does not feel consistent and is usually not practical if mapped using a fixed minimum size over a whole map. At least if map is any larger. When there is plenty boulders about right size it is not worth measure is a boulder 1cm higher or lower than the limit. Some boulders stand out, better map those if about right size within half meter or so. And for steep areas with big cliffs it better to not map too small cliffs to show where one can pass and because small ones does not stand out there, but cliffs with same size may stand out if it locates in flatter place so worth mapping there.

So, even if a good mapper may have a minimum size boulder for a map it should not mean we can expect all boulders that size are mapped and none smaller ones aren't. And missing boulder or extra boulder is an mapping error.

(Even karttapullatin does not have fixed minimum size for cliffs - minimum used is based on steepness of the surrounding area. Fixed size would make steep ridges black and nice tiny cliffs form flat areas would disappear - tried that, did not work in practice).
May 2, 2017 3:07 PM # 
Would the area have been better with more boulders mapped, or fewer, or best as it was?

I may post snippets of my current mapping project with minimum 1m boulder size, with minimum 1.5m boulder size, and with minimum 2m boulder size, maybe also some photos. The terrain doesn't feel as rock strewn as that photo shows (only a few boulders visible most places, in mostly high visibility forest), but with 1m boulders mapped, the map looks overwhelming to me. But I'm interested in others' views.
May 2, 2017 7:26 PM # 
Can a mapper set a local standard different than the 1 meter cutoff? In our area, there are very few boulders. So a knee-high boulder (about 0.5-0.6 meters), if it's not covered with moss, is pretty prominent because it's so rare to find any at all. Also, as others have noted, the overall size (not just the height) of a boulder has a lot to do with how prominent it is in the field.
May 2, 2017 8:59 PM # 
The specification indicates that the boulder "should" be higher than one meter, but "is" immediately identifiable on the ground. (In Colorado, due to lack of moss, nearly every block of rock down to knee high is immediately identifiable from a distance at a run, unless under a juniper or deadfall. But, many places also have lots of rock features, so I'm actually contemplating a higher standard than one meter.) How big a wiggle room that "should" leaves is an interesting question. Then again, for local events, exact compliance with ISOM may carry less importance than having lots of control sites so that not every event uses the same locations. A World Ranking Event might require a standard close to one meter, similarly a national championship, but otherwise, pragmatism may make sense.

(By the way, for non-championship maps of small areas, one could conceivably use the large stony ground dot for, say 30-60cm high blocks of rock. Not the ISOM intention (violates the minimum area of stony ground), but for a local scout camp, I did this to afford them more control locations.)
May 2, 2017 9:39 PM # 
"for non-championship maps of small areas, one could conceivably use the large stony ground dot for, say 30-60cm high blocks of rock"
I did exactly that recently for a small map. I got the idea from one of Australia's best mappers, the late Eric Andrews, who used that method extensively on a map I set courses on.
On your larger question, I don't think you can reasonably ask someone running past one side of a boulder to work out whether it is 0.9 or 1.1m and therefore not on the map or on the map. Without having seen the terrain I'd be tempted to map it as stony ground or boulder field (if it impedes running) or leave them all off (if you can still run fast).
May 3, 2017 2:32 AM # 
@Jim, as a runner, and mapper, I am not a fan of mapping boulders which are around 1m on the downhill side, and much less on the uphill. In the NE US, leaves gather on the flat uphill side, making them unidentifiable as boulders from above. If there is room, and the boulder wide enough, I would map as a small cliff, otherwise, leave it off.
May 3, 2017 3:55 AM # 
This uphill/downhill thing irks me. I've met a mapper who claims that a knoll WAS 1m on the down side. Well, I reckon a boulder, knoll, depression needs to comply no matter which side you approach it from, so the 1m threshold has to be ALL ROUND.

Absolutely agree that the mapper may use a higher threshold according to circumstances. And even on the same map. The afore-mentioned Eric Andrews famously said, "I ask myself which rock puts its hand up, and says, pick me!"
May 3, 2017 6:42 AM # 
Can a mapper set a local standard different than the 1 meter cutoff?

Of course. 1m is just the minimum.

204 Boulder
A distinct boulder (should be higher than 1 m), which is immediately identifiable on the ground.

So mapper can select for example 1.5m cutoff. And vary that around the same map to map only immediately identifiable distinct boulders, as long as smallest ones are about 1m. But of course some commons sense should be used when what taking smaller boulders than the selected cutoff. Even if 1m is the minimum you probably should not take any 1m boulders if your cutoff is 2m, maybe just ~1.5m ones from parts win no much boulders and only small ones. This all is fine by ISOM and OK for WRE/WOC mapping ISOM does not say 1m is the cutoff and all 1m boulders must be mapped (and same applies to cliffs).
May 3, 2017 8:20 AM # 
This discussion makes a mockery of the Canberra map I ran on a couple of years ago with 0.3m termite mounds mapped in low visibility terrain. Some of them were even used as control sites.
May 3, 2017 10:48 AM # 
I'm pretty sure that map makes a mockery of itself.

So mapper can select for example 1.5m cutoff.

Or 0.9. Or 0.8. Or 1.25.
May 3, 2017 6:26 PM # 
@JimBaker "should" be higher than one meter, but "is" immediately identifiable on the ground.
Did I read "immediately identifiable" differently to you?

I think it means that if you ask "What do you see over there?", and the answer is "a single rock", then it can go on, even if it's <1m.

You're saying that if you ask "What type of thing is this?" and the answer is "I can't tell because its covered in moss" then it should be left off?

@gruver - "I ask myself which rock puts its hand up, and says, pick me!"
I like it! There are lonesome rocks round here <1m which pass the test and the "should" gives us wriggle room to put them on.
May 3, 2017 7:18 PM # 
Boulder A distinct boulder (should be higher than 1 m), which is immediately identifiable on the ground."

Usually the key logic words are "and, or" or similar. Here the meaning hinges on parentheses, which I think is fair to interpret as further subordinating the "1 m" clause, and yielding emphasis to the "identifiable" concept.

This seems to be the consensus interpretation , myself included, although I have to admit pleasant surprise at this section of the new ISOM.
May 3, 2017 7:29 PM # 
Graeme: immediately identifiable on the ground.

I think it means that if you ask "What do you see over there?", and the answer is "a single rock", then it can go on, even if it's <1m.

Yes, this. I'm just saying that Colorado rocks are typically very immediately identifiable, even if very small. I can see even tiny blocks of rock from a hundred meters, typically, at a quick glance. Other places, things like moss make them less noticable, and thus a 30cm high rock might be hard to see while running. Some places the coating of stuff that they get makes them the same color as the forest floor.

Please login to add a message.