In theory, I suspect you could get quite a good idea of the depth and thickness of heather from lidar - a combination of the difference between first and last returns and the number of intermediate returns. A quick google has failed to identify an easy way of doing this in practice, although I would be surprised if nobody has tried it - it has obvious relevance for the management of grouse moors. (If there isn't already something out there, it may be a nice project for someone doing a dissertation in geomatics.)
Undergrowth screen does, of course, obscure detail, but that is as true in forests as it is in open areas. People generally don't argue that we should leave large areas of thick brambles off forest maps in the name of legibility.
Rough Open Runnability
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Re: Rough Open Runnability
British Orienteering Director | Opinions expressed on here are entirely my own, and do not represent the views of British Orienteering.
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Scott - god
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Re: Rough Open Runnability
Parkino asked for examples.
Only a small area, but undergrowth hashing was used in a non-standard way here to indicate the approx. extent of the worst and slowest tussocks in rough open.
https://www.sroc.routegadget.co.uk/rg2/#415
Only a small area, but undergrowth hashing was used in a non-standard way here to indicate the approx. extent of the worst and slowest tussocks in rough open.
https://www.sroc.routegadget.co.uk/rg2/#415
curro ergo sum
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King Penguin - addict
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Re: Rough Open Runnability
The ESOC/TAY map of Newtyle Hill used to have a purple screen showing the deepest heather: https://www.esoc.routegadget.co.uk/rg2/#18
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Re: Rough Open Runnability
I don't quite understand why you wouldn't use the Broken ground symbol for tussocks if they're bad enough to map. (And they often are - my ankles hate tussocks - The slog accross the top on Winter Hill fell race did me every time). They're not really undergrowth and there's now a specific symbol for it.
Maybe it was mapped before that was put into the ISOM revision?
And I don't like the purple screen - too easily confused with OOB, and on my computer screen it looks difficult to see anyway.
It'd be interesting to see a version of the Newtyle map with the purple screen -> normal undergrowth screen to see the difference in contour readability.
Maybe it was mapped before that was put into the ISOM revision?
And I don't like the purple screen - too easily confused with OOB, and on my computer screen it looks difficult to see anyway.
It'd be interesting to see a version of the Newtyle map with the purple screen -> normal undergrowth screen to see the difference in contour readability.
- rf_fozzy
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Re: Rough Open Runnability
by Scott » Fri Mar 03, 2023 12:14 pm
In theory, I suspect you could get quite a good idea of the depth and thickness of heather from lidar - a combination of the difference between first and last returns and the number of intermediate returns. A quick google has failed to identify an easy way of doing this in practice, although I would be surprised if nobody has tried it
I use Kartpullautin to process the LIDAR vegetation readouts. Fiddling with the “vegemode” settings changes the appearance of undergrowth on open areas. It isn’t accurate enough to be gospel, but it helps to focus on areas for foot surveys. There is more at the bottom of page 1 of this;
viewtopic.php?f=1&t=15778
- Davy
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Re: Rough Open Runnability
Thanks for those examples. How did people get on with the purple hash on Newtyle. (Quick look at routes suggests they couldn't really avoid the heather.)
I have been able to identify deep heather using (point cloud) LIDAR data on the moor east of Chatsworth. I try to adjust the height range parameters in OCAD to pick out low vegetation and on East Moor found a high correspondence with where I'd had to wade through the stuff (heather) on an exploratory run. There are also stands of deep bracken on the moor, like Burbage, these would be relatively fast in the off-season and impenetrable through the summer. They are more prominent than deep heather and therefore more useful for navigation, but for route choice (and course planning) info on the depth of heather is valuable.
I have been able to identify deep heather using (point cloud) LIDAR data on the moor east of Chatsworth. I try to adjust the height range parameters in OCAD to pick out low vegetation and on East Moor found a high correspondence with where I'd had to wade through the stuff (heather) on an exploratory run. There are also stands of deep bracken on the moor, like Burbage, these would be relatively fast in the off-season and impenetrable through the summer. They are more prominent than deep heather and therefore more useful for navigation, but for route choice (and course planning) info on the depth of heather is valuable.
- Parkino
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Re: Rough Open Runnability
buzz wrote:Burbage is mapped for the worst case summer runability and for much of the year its often more runnable than the heather which makes route choice even more unfair.
Map specifically said winter vegetation at the top
buzz wrote:Some notes in the final details might have helped as would courses planned to avoid the worst of the heather.
Controls were deep in the heather (for the affected courses), the worst could not be avoided. Even fast people were wading in places. Depths varied from around 20cm (runnable) to mid-thigh.
- sborrill
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Re: Rough Open Runnability
rf_fozzy wrote:I don't quite understand why you wouldn't use the Broken ground symbol for tussocks if they're bad enough to map.
I may be wrong but I've always understood 'broken ground' to mean areas of knolls and/or depressions that are too detailed to map individually and are mapped as a brown land form feature. Tussocks are a smaller scale and a vegetation feature which seem to fit with the green stripe undergrowth symbol.
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buzz - addict
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Re: Rough Open Runnability
Useful definition of broken ground with example photos.
https://omapwiki.orienteering.sport/symbols/113-broken-ground/
https://omapwiki.orienteering.sport/symbols/113-broken-ground/
- tropso
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Re: Rough Open Runnability
I have used broken ground to show old sitka spruce clear fell stumps, waist high, three meters apart on rough ground.
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Re: Rough Open Runnability
Just to be clear as the mapper, I mapped the bracken on Burbage as a separate screen which could be switched on for summer or hidden for winter/spring events. I did expect the screen to be hidden for the recent Burbage event but event officials decided to leave it on as it was assessed to be accurate for navigation. I agree that this gave the impression that the bracken was slower run than the rough open heather. But mappers do need some guidance here as rough open can include long grass, tussocks of various height, bracken and heather of varying depth. But including a runnability screen will affect legibility. In the case of Burbage it is a probably a better representation in winter if the undergrowth screen is applied to the heather and not the bracken. This is not just about rough open. At the recent BNC much of the white forest should have had an undergrowth screen in the white forest which contained slow run/walk tussocks - path runs were definitely faster than white forest.
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