Discussion: how to map clearing overtaken by vegetation

want to modify a map that shows a rough open clearing, which has been overrun by vegetation, a thick set of small trees 4-5 meters high. To get through, one must slow down to a slow walk. My first thought was to draw light green, but the area still feels very "open", and the surrounding mature forest is visually clearly identifiable. The surrounding mature forest has also various shrubbery and thorny bushes, making it light green. If I draw light green into the clearing, then the demarcation between mature forest and what was once the clearing loses any identifiable feature, being both areas light green. So, what to do?

How about the rough open symbol, with vertical green lines indicating undergrowth?

small trees 4-5 meters high is not exactly undergrowth...

If the best symbol for the "clearing" is indeed light green, then you could indicate the edge with a vegetation boundary. But I agree that a colour difference might be good too. Consider 404 rough open. Consider (for the map as a whole) using green dots instead of white dots in 404.

Although not technically undergrowth, I think adding the vertical green lines and perhaps a veg. boundary does a good job of letting the competitor know what to expect from these type of transition areas. But i'm curious to hear any other suggestions.

I've seen Gruver's suggestion of green dots in 404 used in another type of transition area where cedar trees are beginning to take over a rough open clearing, and it does a good job for that situation - reasonably fast movement between the trees, but you have to weave your way though them. But I don't think it does as good a job representing Sherpes situation where the running is slower throughout.

If it is thick, and the surrounding area is also thick, then you wouldn't put a control in there, and the majority of competitors will run around it if it is on their route, so why do you need to differentiate between the two types of thick - draw it all green!

Sounds to me like the surrounding forest should be light green, the former clearing should be medium green, and vegetation boundary dots should show the transition. Using vertical green lines would be a misuse of the symbol that is supposed to show "good visibility".

How about requesting the landowner burn the area this fall? No map modification then necessary. :-)

Agree with jj.

Some mappers try to differentiate same greens by trying to use patches of white if possible for the other and yellow for the other. And white to make boundary stand out more. But it may just clutter the map for no reason.

just to help out in "visualizing and feeling" the vegetation, these small trees are vertical strands of trees, each with a trunk of 2-6 cm wide, and each separated from a nearby tree by 5-20 cm, meaning that the runner/walker would have to push his/her body through, as in wedging through, slowing down to a slow walking speed.

I'm not a mapper but that sounds more like fighting your way through and not light green. Regardless, it sounds like there should be black dots for the vegetation boundary

+1 what jjcote suggests. From your description this patch is not light green

Dark or medium green please.

Yeah, that's a good description of dark green ("traditional" dark green, not the special extra-dark sprint green).

In a similar situation, I overprinted purple OOB for my immediate event, and before I could get corrections to the club mapper, someone cut it back to clearing. Phew

One plea on a side issue, if you can push through, at even a slow stumble, it should be medium green, not darker. It is critical to save dark green to highlight the extreme case vegetation, that is indeed impassable for practical purposes. I think this is the single most important issue in the whole white to green array (not that there aren't other important issues).

The main thread is a tough call. Remember this was the underlying issue at this year's WOC Middle Final, 2nd last control.

I think the key points have been well presented, not that I agree exclusively with any of them.

I'll bring up an additional consideration, and that is the size and visual significance of the "clearing". If, when viewed from a typical viewing distance, this 4-5 m vegetation looks like a clearing compared to the surrounding forest, I think there can be value in highlighting it as yellow (+green lines), as a navigation feature (within normal clutter guidelines). This certainly applies to smaller "clearings", where searching for a control inside the area is not a concern.

A similar principle applies to clearings that are practically impassable, typically thorns, requiring dark green by the book, but their navigation value as a yellow feature (+green lines) adds more real value to the map. Precise runnability of a relatively small area is not a concern if it is easy to run around.

I have seen many clearings like this that made perfect sense to me, and mapped some myself.

And oh yes, the small clearings with lines have to meet the min. size requirement for the green line symbol, in order to get meaningful lines within the feature.

Get the mower out and cut down tracks through it, then map it as 'Track - difficult to ride' and set a World Champs event there.

> "but their navigation value as a yellow feature (+green lines)
> adds more real value to the map"

I find that true specially in the summer with the forest having a thick canopy of leaves and dark shadowy grounds, and where one can very distinctly see a bright source of sunlight hitting a clearing. However, that "clearing" is now a morass of vines 3 meters high that is practically impassable.

I would endorse Eric's call to save 410 for really really bad stuff. I don't use much of it, after an experience worming my way through some gorse for 1km in an hour. I wasn't orienteering, but that suggests about 10% speed. It only has to be half as bad to fall within 408.

I wasn't orienteering

You mean there are other things?

On the subject of the speed of green:
The ISSOM states specific relative speeds for greens. White is 100-80% speed and dark green is 20-0%. Using the example used in the ISSOM document if 100% speed is 5 min/km through white forest than the max speed one can theoretically go in dark green is 25min/km.

In more understandable terms that means that in one minute you can travel up to 40 m. That's pretty slow but it's not impassable.

That said, I agree that as a practical reality the suggestion to save dark green for the 'really really bad stuff' is a good solution but be aware that it doesn't have to be truly physically impassable to be mapped as dark green.

I thought impassable green only existed in ISSOM. The ISOM version doesn't have the really dark one so it's as you have explained, although in reality it could also be impassable.

Note that a truly impassable (and forbidden to pass) green appears in the 2013 draft of the ISOM revision (and the runnability percentages for some other greens are adjusted). So the impassable green may appear in ISOM 2016 (or whatever year it will be published).

Well that's just great.

You mean there are other things?

Yes. Rogaining.

20-0%. That's pretty slow but it's not impassable.
This is a really bad standard. The map is there to tell the orienteer which way to go, it shouldn't introduce random time gains.

Suppose there's a 20m band of green, or I can run an extra 200m to go around it, taking say 90sec. If its 20% passable, I can save a minute by going straight. 4% will cost me a minute. Easily a winning margin, and there's no way to tell from the map which to do.

There needs to be a green symbol which means "under no circumstances is it correct to go through here". Eric is spot on: this is *the* biggest source of unnecessary ISOM-induced unfairness.

"forbidden to pass" is a bit different, because it suggests an obligation on the organiser to disqualify people. But using the same symbol is OK (IMO) since:

(a) the information needed by the competitor is more or less the same - "Go round"*.
(b) getting stuck in something truly impenetrable and having to backtrack is punishment enough.

Darkest green isn't any different from impassable cliff or marsh. One may take risk and manage to get trough and impassibility may depend on season. The thing is you just simply don't plan legs/courses where one can gain advantage by going trough impassable something. So if someone misses the best route and hits green he will loose time for having to fight trough or track back, but looses time anyway. And if you really can't avoid such legs, you put purple threre to tell it is not OK to cut trough. That's why it is just fine and there is no that much fairness issues here. But of course bad planners can always plan courses with fairness issues.

If it takes 90 seconds to run 200m, you are not going to win anyway :P

Shrepes, I reckon this 'clearing' should be mapped as mid-green (408), with veg boundary.

Gruvver, how do you change the white dots to green in 404? I can only change the colour of the background (yellow 70%). (Still working in OCAD 8)

Agree with Jagge, apart from one issue: hedges. The impassable hedge symbol from ISSOM would be useful in ISOM to distinguish hedges which are impossible to cross from those that are very difficult. (Yes, we have areas in the UK where this distinction is crucial and difficult to avoid.)

I guess you are right. But can you give example Parkino, link to a map/course? Just to figure out how complex or unusual such cases are.

Don't listen to Gruver. New Zealanders specialise making up their own non-ISOM symbols so pale yellow with green dots falls into that category!

Parkino, is the problem is the hedge minimum width is0.25 mm and the width of symbol 707 is 0.7 mm. So with two parallel hedges side by side you may still be able to leave enough white space between hedges but with three hedges it may not possible. So the problem is tree or parallel hedges close together and you really need to allow running in between all of them? How common is that case really, sounds pretty rare to me?

Parkino in Symbol edit you select the structure tab, then the edit button, then select the centre dot and change the colour from white for yellow to green.

Jagge, if the hedge lines are drawn with the (new ISOM symbol or existing ISSOM) symbol for impassable vegetation why would you also need to use 707?

I did once make a sprint map where there were two parallel hedges (with a fence between them!) but no competitors were going to go between them anyway - as you say, it would be rare.

I still say sherpes should just make the whole area green, if only to prevent some pesky course setter from using the former clearing or it's boundary as a control site.

It is boundary!

if the hedge lines are drawn with the (new ISOM symbol or existing ISSOM)

There is no such symbol in current ISOM and not thought to be needed because purple color exists. The principle in ISOM is used to be everything forbidden is marked with purple. Simple, clear and obvious. It is shame if that gets changed.

But I am still waiting for some map examples of difficult/impossible hedge cases, there may be rare difficult cases out there, multiple parallel hedges close together and course crossing there making competitors approaching it several times and from from different directions.

I quote from ISOM2000. "Where there are scattered trees in rough open land, areas of white (or green) should appear in the tone." A rereading of the bible once in a while can turn up some useful things..

Could be interpreted in different ways... just like the Bible.

Well I just looked in the ISOM 201X link and it seems that actually may be a symbol in future, which makes a lot of sense in an orchard with unmowed lawn!

Realize that my good friend Sherpes is a hasher. As such, he sees our medium green as his light green. He believes that our medium green would be the ideal spot for a sun-bleached flag, especially if there was any possibility of using a 40 cm ant hill.

What's wrong with a distinct boundary of a green area as a control site?

I did this recently; now I'm wondering if I was remiss.

I think the issue is if it's green within green.

Yes that's what I said tRicky. But also only use a vegetation boundary as a control site if it is very, very clear on the ground.

And a note to mappers, definition of 416: A distinct forest edge or very distinct vegetation boundary within the forest. Lets look at both parts of this in turn. If 416 was drawn around every forest edge, not only would the map look cluttered, but you are also defying biology since left to nature the boundary would inevitable change. For the same reason, a patch of green or yellow in an otherwise white forest should not require a vegetation boundary since the boundaries WILL change. For me, that only leaves a case for 416 to be used for the edge of a plantation or a boundary between two plantations of clearly different species or sizes of the same species.

One of those maps that Richard put up at the O dinner a few weeks ago seemed to have the forest boundary symbol around practically everything. It looked very cluttered.

The best solution for thinly vegetated clearings is to hold a rogaine.

Seriously though, that quote gruver provided makes me wonder if it would be appropriate to modify symbol 404 (rough open with scattered trees), but replacing the white screen with green, to indicate the runability better.


I see no issues with symbol 416, it doesn't defy nature any more than any other mapping symbol (even mountains flow before the lord...). Many naturally occurring vegetation boundaries are formed due to changes in the underlying geologic/soil structure, and can persist for remarkably long times. (As a dramatic example, see the serpentine prairie)

For me, that only leaves a case for 416 to be used for the edge of a plantation or a boundary between two plantations of clearly different species or sizes of the same species.

Oh god, I agree with Simmo on something. :)

blegg - in our typical local terrain we get a lot of relatively sharp changes across spurs/ridges from one species to another...but even then the change is spread over 10-20m. You'd want it to be a lot sharper than that to be worth mapping, and that generally means something man-made.

Sheoak anyone?

Sheoak tends to be worth mapping as light green though, given the amount of fallen crap that goes with it. We're talking about really distinct changes in vegetation that don't change runability...(because otherwise you've got the change between white/green/other green to signify the boundary)

You may have forgotten what sheoak looks like though Tooms, since it'd be light yellow compared to the scrub around Albany... :)

Ah, I didn't register the change in runnability factor - I was kinda reminiscing about the sheoak thickets on Mt Yetar (and similar) where we run through waist high prickly moses and associated crud slowly, then smack into clearly visible sheoak. Arguably the waist high stuff shouldn't be white, but it's pretty easy to read at the moment by just *knowing* the sheoak is medium green and everything else is variable white!

We have some areas in my part of the world where an exclusively deciduous (oak-maple) forest transitions abruptly to a coniferous (hemlock or maple) grove, usually not in a straight line. Very different looking, especially when the leaves are off. The vegetation boundary is useful there, moreso than the superfluous indication that an open field has a distinct edge (though that has thankfully fallen out of fashion, I think). But not all such species transitions are worth mapping, and too many will in fact clutter up the map, especially if there's already a lot of black. I particularly dislike the "less distinct vegetation boundary" that one mapper around here has invented, where the dots are spaced twice as far apart, and which indicates something you can't really see and which just looks like randomly placed dots.

Sounds like the newly proposed ISOM 'very broken ground', which is exactly like broken ground but with more dots and with 'very broken ground', you're allowed to put the dots closer together than you are under 'broken ground'. Sounds dumb?

There have been some comments that seem to suggest that there should never be a distinct veg boundary symbol when the forest changes from one level of green to another. I don't agree with this. There can be forests where it starts out light green and eventually becomes medium green, but the change is more gradual than distinct. The mapper, at some point, decides that it has gotten thick enough that it now needs to be medium green. That would certainly be indistinct. But there are other places where it changes from one type of vegetation to another, the result of which is that it changes from light green to medium green but very distinctly. Why wouldn't a distinct veg boundary symbol be appropriate to differentiate the two situations?

You may be right RLS, but the only instances where I can see there might be a distinct boundary are, as I said plantations. In any case, the point I am trying to make is don't put controls in green on vague features - and mappers can help that by not tempting course setters through mapping such features. If there is a really distinct boundary within green areas I probably still would not map it, because I wouldn't want my map to be remembered as yuck - horrible green stuff everywhere. I'd be wanting course setters to use the runnable areas of my map, with the green there purely to offer route choices.

Another Simmo map!

Sorry, Jagge, been away.

To clarify, my concern is to distinguish between hedges than are impenetrable e.g. 2m high and 1m thick and hedges which may be penetrable (in some places), typically less thick. So it would perhaps be analogous to the high fence/fence, or an impassable cliff/passable cliff distinction, except that there is no chance to pass through these hedges. However, green does not connote impenetrability.

It is an issue which occurs in the National Forest, a plantation project where arable fields, including their hedges, have been converted to wood. There are more hedges than you would typically expect in a wood.

In the area, I'm mapping there are narrow grassy rides alongside many of these hedges, sometimes on both sides. Purple over-print is a solution, but it's supposed to be off-set so the feature is visible. So, it could not be used in those later cases.

(I'm afraid I don't know how to add an image to a comment.)

Gruver, thanks for the instructions.

I solved the semi-open issue by using undergrowth screen(s). I was confronted by areas which were semi-open in nature, but the trees were hawthorns, in small groups, 2-3m high, too diffuse to map meaningfully, but much less runnable than 404 implies (for us in the UK, at least).

The green dots are something for the future (as ISOM guidelines hint).

In my experience, it's not infrequent for medium green to represent an overgrown clearing, with thick saplings and/or bushes, since a fair bit of difficult to run vegetation comes about this way. If I saw a patch of medium green on the map about where I saw a burst of sunlight in the terrain, I'd likely think "ah!", and not be confused by the lack of yellow. It's similar to orienteers using vegetation, rather than water, as a sign of a marsh, it seems to me. The orienteer uses a lot of their knowledge of the natural world to navigate.

If this won't suffice to make everyone happy, then pay the landowner to cut a "corn maze" in the overgrown clearing, in the shape of the club logo. Then you've given yourself an excuse to put patches of yellow in the green, added navigational challenge and potential control locations, and reduced the need to spend map layout space for the club logo. :-)

Something I saw yesterday that brought back to mind past discussions of when to use dark vs medium green:

That green topiary is definitely dark green (410.0), and the Ilex verticillata must then be medium green (408.0) pic.twitter.com/QhT9vUHVLb

— West PA Orienteering (@wpaorienteering) February 14, 2016

Or they might both be dark green...

The one on the left looks red.

Those both look like out of bounds 421 green, or olive green to me.

Only on a sprint map.