Discussion: Mapping the Forest or the Trees
in: Orienteering; General
Mar 7, 2009 10:04 PM
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So I'm looking to learn mapping and update a small map in the club's library - a good training lesson for me and helpful all around. Out on a "compare the existing map to what I see" run this morning, I came to see a sticky issue of mapping...
A completely clear, mowed area of a park is clearly bright yellow, and if a large area has one or two trees, they can be marked distinctly.
On the other side a forest with little undergrowth is clearly identified in white.
And between these two you might find an open area with scattered or isolated trees - marked with dotted yellow on white...
So - when does clear with individual tress become clear with isolated trees? And when does clear with isolated trees become clear forest?
"It depends" is an answer that I already understand - I'm looking for some rules of thumb or guidelines you use when mapping.
The individual trees are more useful for control locations, but at some level become difficult or time consuming to map well.
Consider a scenario - a 10m wide stream with 2m of brush along the edge. This is then bordered by 20m of isolated trees with a gravel road through the middle. Open park land then stretches for a very long distance.
The trees on the inside of the gravel road might be mapped individually - and are quite significant (say 2m in diameter).
As I thought of how to describe the image I had in mind, I believe I've "answered" what should be done - come up with a consistent, logical strategy - and use it throughout. [so lesson learned there]
But I still think you'll be able to give me some good anecdotes and experiences to learn from;-)
A completely clear, mowed area of a park is clearly bright yellow, and if a large area has one or two trees, they can be marked distinctly.
On the other side a forest with little undergrowth is clearly identified in white.
And between these two you might find an open area with scattered or isolated trees - marked with dotted yellow on white...
So - when does clear with individual tress become clear with isolated trees? And when does clear with isolated trees become clear forest?
"It depends" is an answer that I already understand - I'm looking for some rules of thumb or guidelines you use when mapping.
The individual trees are more useful for control locations, but at some level become difficult or time consuming to map well.
Consider a scenario - a 10m wide stream with 2m of brush along the edge. This is then bordered by 20m of isolated trees with a gravel road through the middle. Open park land then stretches for a very long distance.
The trees on the inside of the gravel road might be mapped individually - and are quite significant (say 2m in diameter).
As I thought of how to describe the image I had in mind, I believe I've "answered" what should be done - come up with a consistent, logical strategy - and use it throughout. [so lesson learned there]
But I still think you'll be able to give me some good anecdotes and experiences to learn from;-)
Mar 8, 2009 12:03 AM
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My philosophy about how I interpret your question ("when does clear with individual tress become clear with isolated trees? And when does clear with isolated trees become clear forest?") --
- Open land (yellow) should be truly open (no trees), or else map the individual trees.
- If there are too many trees to realistically map individualy, then map as "open land with scattered trees", if it is indeed open land, and not open woods (white). (see below)
- For the second part of the question, when does it change from open land with scattered trees, to open woods, I generally am guided by what's on the ground between trees. If it's grass on the ground, then I would tend to call it open land with scattered trees. If it's more "forest" type stuff (basically anything except for grass -- assuming of course that it doesn't present a significant deterrent to progress, which would make it not "white"), then I would map it as open woods (white).
That has been my approach in recent years, in our area (upstate NY). People in other parts of the country with different terrain and vegetation might well do something different.
- Open land (yellow) should be truly open (no trees), or else map the individual trees.
- If there are too many trees to realistically map individualy, then map as "open land with scattered trees", if it is indeed open land, and not open woods (white). (see below)
- For the second part of the question, when does it change from open land with scattered trees, to open woods, I generally am guided by what's on the ground between trees. If it's grass on the ground, then I would tend to call it open land with scattered trees. If it's more "forest" type stuff (basically anything except for grass -- assuming of course that it doesn't present a significant deterrent to progress, which would make it not "white"), then I would map it as open woods (white).
That has been my approach in recent years, in our area (upstate NY). People in other parts of the country with different terrain and vegetation might well do something different.
Mar 8, 2009 12:08 AM
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My desire, as a runner, is to have it tailored to the runner.
What will the runner see at 75%+ speed?
What will the runner see at 75%+ speed?
Mar 8, 2009 1:00 AM
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I'll take a stab at a partial answer to part of the question, the transition from white forest to semi open ("dotted yellow on white" 402).
Look at the ground vegetation. Try to mark the change from the predominant forest ground cover, to the predominant open ground cover. In my region this usually means the transition from leaf cover to mowed grass (unmowed grass if we're dealing with rough open 403 and rough semi open 404). Sometimes in well used "parkland" settings you run into bare ground, in which case you are screwed, and need to look for another guideline :-)
The principle about paying attention to ground vegetation applies to many other mapping dilemmas, not the least of which is water features. Ground vegetation type is probably the best indicator of long term conditions, and is also arguably in the prime perception area of orienteers, certainly moreso than higher canopy level details.
For the transition from semi open to open, I would only offer a long list of "it depends". One would be, what is the final map scale, and symbol set (ISOM, ISSOM) you are working with? Another "it depends" would be, how many trees are already shown on your base map,? Obviously this isn't the best guideline, but admittedly it sometimes comes down to this pragmatic level. And the list goes on, to say nothing of the responses.
Its not easy to find a single guideline that tops yours, "come up with a consistent, logical strategy - and use it throughout".
I'll throw out an additional (rhetorical?) question, when should you delineate using the edge of canopies, and when should you map along the line of tree trunks?
A good topic, I believe worth asking "in public", but the o-map group is also a good place for this.
PS- The two posts above were made while I was composing. I see RLShadow makes similar points.
Look at the ground vegetation. Try to mark the change from the predominant forest ground cover, to the predominant open ground cover. In my region this usually means the transition from leaf cover to mowed grass (unmowed grass if we're dealing with rough open 403 and rough semi open 404). Sometimes in well used "parkland" settings you run into bare ground, in which case you are screwed, and need to look for another guideline :-)
The principle about paying attention to ground vegetation applies to many other mapping dilemmas, not the least of which is water features. Ground vegetation type is probably the best indicator of long term conditions, and is also arguably in the prime perception area of orienteers, certainly moreso than higher canopy level details.
For the transition from semi open to open, I would only offer a long list of "it depends". One would be, what is the final map scale, and symbol set (ISOM, ISSOM) you are working with? Another "it depends" would be, how many trees are already shown on your base map,? Obviously this isn't the best guideline, but admittedly it sometimes comes down to this pragmatic level. And the list goes on, to say nothing of the responses.
Its not easy to find a single guideline that tops yours, "come up with a consistent, logical strategy - and use it throughout".
I'll throw out an additional (rhetorical?) question, when should you delineate using the edge of canopies, and when should you map along the line of tree trunks?
A good topic, I believe worth asking "in public", but the o-map group is also a good place for this.
PS- The two posts above were made while I was composing. I see RLShadow makes similar points.
Mar 8, 2009 5:47 AM
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Sounds like you are mapping parkland which would mainly be used for sprint races at 1:5000 (or 1:4000). This is a good reference from 2006 WOC mapper Kell Soenniksen.
http://www.soenniksen.dk/sprintkort/gb.htm
It specifically addresses some of your questions.
http://www.soenniksen.dk/sprintkort/gb.htm
It specifically addresses some of your questions.
This discussion thread is closed.