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OS map 5m contours



 
 
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  #11  
Old May 6th 09, 12:29 PM posted to uk.rec.walking
Jhimmy
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Posts: 690
Default OS map 5m contours


"Peter Clinch" wrote in message
...
Roger wrote:

AFAIK all the First Series 1:25,000 contours were at 25 foot intervals
which don't translate easily into multiples of 5 metres so the OS saw an
opportunity to cut costs by dispensing with 5 metre contours on steep
ground.


"Extra detail" is not always a good thing. There's already no shortage
of mapping areas where the 10m interval is really too small to get
enough clarity and even without all the symbols obfuscating things
there's just too much brown in some places.

Norwegian highland areas are mapped with a 20m contour interval and
though it takes a bit of getting used to it actually does make a lot of
sense in places with a lot of relief. Harveys use a 15m interval which
IMHO works rather better than 10m in quite a few places in Scotland.

A 5m interval at 1:25k is not effectively much different from 10m at
1:50k. There's no problem finding instances in the Highlands on
Landrangers where contours are missed out because of lack of space,
giving a false impression of the steepness of the land.

Orienteering maps usually use 5m contours, and are most usually 1:10K,
sometimes even larger scale (1:3k the most extreme I've used). They
sometimes use intermediate contours shown as dashed "form lines" where
topographic detail is clearly visible on the ground that would be
swallowed up by conventional contouring. I think the "form line" system
is a good one as it's optional and only used by discretion where it
helps. A standardised contouring system used for both the Fens and the
Cuillin ridge, OTOH, does run into problems that what's good for one
place may not work in the other.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/



Last year I was on Beinn Achaladair using my old Outdoor Leisure 25k map
there was far too much detail on it. When I got back home and looked at the
50k it was far clearer - if you get the gist.

You've come up with a good point about the Fens and Cuillin using the same
standard contours.

Jhimmy

  #12  
Old May 6th 09, 01:50 PM posted to uk.rec.walking
Phil Cook[_2_]
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Posts: 826
Default OS map 5m contours

Jhimmy wrote:


"Peter Clinch" wrote in message
...
Roger wrote:

AFAIK all the First Series 1:25,000 contours were at 25 foot intervals
which don't translate easily into multiples of 5 metres so the OS saw an
opportunity to cut costs by dispensing with 5 metre contours on steep
ground.


They also dispense with contours between the 50m ones on the 50k where
it becomes hard to squeeze all four in. There's a bit on Beinn Eighe
where they haven't and it just turns the hill into an orange mess.
Mind you nobody in their right mind would go that way on foot.

A standardised contouring system used for both the Fens and the
Cuillin ridge, OTOH, does run into problems that what's good for one
place may not work in the other.


Last year I was on Beinn Achaladair using my old Outdoor Leisure 25k map
there was far too much detail on it. When I got back home and looked at the
50k it was far clearer - if you get the gist.

You've come up with a good point about the Fens and Cuillin using the same
standard contours.


Except it isn't the contours that make the OS maps of the Cuillin
unusabe for navigation; it's all the black lines denoting crags that
they have rather overdone on the 50k and the "boulders" on the 25k.
--
Phil Cook, last hill: Sgurr na Banachdich
http://www.therewaslight.co.uk
  #13  
Old May 6th 09, 01:54 PM posted to uk.rec.walking
Phil Cook[_2_]
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Posts: 826
Default OS map 5m contours

Dominic Sexton wrote:

In article , Mike Mason
writes
Just been setting up a walk near New Radnor for tomorrow and noticed that in
the area contour lines seem to be in 5 metre intervals rather than 10 metre
intervals. I've never seen this before on an OS map. Does anyone know of
other areas where the contours are mapped at 5 metre intervals and is there
any particular reason for this.


I think it is just where the sheet is generally not very hilly. In
relatively flat areas 10m contours would mean almost no contours!

When I first noticed two adjacent bits of mapping with different contour
intervals I initially thought there was a very steep sided valley
nearby. Turned out the 5m contours made it look that way until I looked
closer!

Here is that example just to the east of Black Hill in the northern Peak
District:

http://www.streetmap.co.uk/map.srf?X...4875&A=Y&Z=115


I don't think you would get adjacent areas on an actual OS printed
map. I think it either one thing or the other.

However, is it me or are the 5m contours on that example just
interpolated from the 10m ones which show rather more detail? I don't
think the character of the ground changes from crinkly to smooth
between the 10m contours on Great Hill.
--
Phil Cook, last hill: Sgurr na Banachdich
http://www.therewaslight.co.uk
  #14  
Old May 6th 09, 02:52 PM posted to uk.rec.walking
Peter Clinch
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Posts: 1,964
Default OS map 5m contours

Phil Cook wrote:

Except it isn't the contours that make the OS maps of the Cuillin
unusabe for navigation; it's all the black lines denoting crags that
they have rather overdone on the 50k and the "boulders" on the 25k.


I would say that the black symbols render it primarily unusable, but if
you took them off it would still be pretty close to unusable afterwards
in any case. And that's with 10m contours, 5m it would just be an
orange-brown blob.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/
  #15  
Old May 6th 09, 06:34 PM posted to uk.rec.walking
Bill Grey
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Posts: 1,117
Default OS map 5m contours

In message , Phil Cook
writes
Dominic Sexton wrote:

In article , Mike Mason
writes
Just been setting up a walk near New Radnor for tomorrow and noticed that in
the area contour lines seem to be in 5 metre intervals rather than 10 metre
intervals. I've never seen this before on an OS map. Does anyone know of
other areas where the contours are mapped at 5 metre intervals and is there
any particular reason for this.


I think it is just where the sheet is generally not very hilly. In
relatively flat areas 10m contours would mean almost no contours!

When I first noticed two adjacent bits of mapping with different contour
intervals I initially thought there was a very steep sided valley
nearby. Turned out the 5m contours made it look that way until I looked
closer!

Here is that example just to the east of Black Hill in the northern Peak
District:

http://www.streetmap.co.uk/map.srf?X...4875&A=Y&Z=115


I don't think you would get adjacent areas on an actual OS printed
map. I think it either one thing or the other.

However, is it me or are the 5m contours on that example just
interpolated from the 10m ones which show rather more detail? I don't
think the character of the ground changes from crinkly to smooth
between the 10m contours on Great Hill.


I've only briefly glanced at this page - it may answer the question.

https://dspace.lib.cranfield.ac.uk/b...Hyman-2003.pdf
--
Bill Grey

  #16  
Old May 6th 09, 06:54 PM posted to uk.rec.walking
Simon Challands
external usenet poster
 
Posts: 507
Default OS map 5m contours

In message
Roger wrote:

AFAIK all the First Series 1:25,000 contours were at 25 foot intervals
which don't translate easily into multiples of 5 metres so the OS saw an
opportunity to cut costs by dispensing with 5 metre contours on steep
ground. A pity it didn't result in more contours and less crag symbols
on the steep ground but the OS really do like filling the maps with
symbols rather than actual detail.


That's one of the symbols I don't mind too much, because it gives you
a better idea of the terrain and how easy it'll be to cover. The lack
of as much in the way of crag / boulder / scree was one of the
problems I've had with French maps.

--
Simon Challands
  #17  
Old May 7th 09, 09:16 AM posted to uk.rec.walking
Peter Clinch
external usenet poster
 
Posts: 1,964
Default OS map 5m contours

Simon Challands wrote:
In message
Roger wrote:

AFAIK all the First Series 1:25,000 contours were at 25 foot intervals
which don't translate easily into multiples of 5 metres so the OS saw an
opportunity to cut costs by dispensing with 5 metre contours on steep
ground. A pity it didn't result in more contours and less crag symbols
on the steep ground but the OS really do like filling the maps with
symbols rather than actual detail.


That's one of the symbols I don't mind too much, because it gives you
a better idea of the terrain and how easy it'll be to cover. The lack
of as much in the way of crag / boulder / scree was one of the
problems I've had with French maps.


Harveys maps have IMHO a much better means of doing it, which is
contours are grey on rocky ground and brown otherwise. So you don't
cover the contour information with symbols and can still see where it's
going to be "interesting" to get down.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/
  #18  
Old May 7th 09, 10:47 PM posted to uk.rec.walking
Mike Mason
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Posts: 158
Default OS map 5m contours


"Mike Mason" wrote in message
om...
Just been setting up a walk near New Radnor for tomorrow and noticed that
in the area contour lines seem to be in 5 metre intervals rather than 10
metre intervals. I've never seen this before on an OS map. Does anyone
know of other areas where the contours are mapped at 5 metre intervals and
is there any particular reason for this.

Mike Mason


Thanks for the input. I think I'll email OS and ask the question. If I get
anything I will post here.

The walk was really quite good. The views down into Harley Dingle and the
range quite excellent. Saw no one about other than a guy on Black Mixen but
he was involved in the radio mast there. Pity there's not more of the walk
but what there was was good.

Mike


  #19  
Old May 8th 09, 09:03 PM posted to uk.rec.walking
Gerald
external usenet poster
 
Posts: 10
Default OS map 5m contours

johngoldfine wrote:
The walk was really quite good. The views down into Harley Dingle and the
range quite excellent. Saw no one about other than a guy on Black Mixen but
he was involved in the radio mast there. Pity there's not more of the walk
but what there was was good.

Mike


I expect to be there in two weeks, 5 m contours, 10, whatever....


Its a nice area and the Whimble is very distinctive and stands out far
more than its two higher neighbours.

Gerald
  #20  
Old May 11th 09, 07:33 PM posted to uk.rec.walking
Richard Webb[_2_]
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Posts: 38
Default OS map 5m contours



Orienteering maps usually use 5m contours, and are most usually 1:10K,
sometimes even larger scale (1:3k the most extreme I've used). They
sometimes use intermediate contours shown as dashed "form lines" where
topographic detail is clearly visible on the ground that would be
swallowed up by conventional contouring. I think the "form line" system
is a good one as it's optional and only used by discretion where it
helps.


In many hill areas of Scotland the contour interval is actually 50m.
The 10m interval breaks down, contours are omitted and effectively
become form lines. It is actually bad form to have more than one
form line between contours on an orienteering map.

AFAIK the highest place on a 5m 1:25:000 map is Ben Cleuch in the
Ochils.

Richard Webb
 




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