OS One Inch - misalignment on A859

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rileyrob
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OS One Inch - misalignment on A859

Post by rileyrob »

I shall start by saying that I don't believe this is an error with Sabre Maps!

The OS One Inch maps show a significantly different loop on the A859 as it climbs up above Loch Seaforth:
https://www.sabre-roads.org.uk/maps/ind ... 9,-6.95969,
There is nothing to suggest such a different line was ever taken when looking at Google Earth, so I thought maybe the OSM trace was wrong, but with no other large scale base maps to check with I couldn't prove it that way. (The OS Six Inch from NLS doesn't even show this road, which appears to have been built in the earlier 1930s, but not mapped as the A859 before the 1950s.
However, by comparing with the current OS 1:25,000 and 1:50,000 mapping, and measuring off the grid squares, I am fairly convinced that the OS One Inch mapping was wildly wrong.

Are there any other occurrences like this where the OS plotted a road so badly?
Rob.
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Steven
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Re: OS One Inch - misalignment on A859

Post by Steven »

rileyrob wrote: Mon Apr 18, 2022 13:58 However, by comparing with the current OS 1:25,000 and 1:50,000 mapping, and measuring off the grid squares, I am fairly convinced that the OS One Inch mapping was wildly wrong.
What's even more interesting is just how long that lasted and on how many different scales - I can see it going back as far as the Scottish Popular Edition of 1947; and the various Quarter Inch Fourth Edition and Fifth Series sheets from 1936 onwards show the same loop as the One Inch, though it's not that clear on the Fourth Edition sheets. It's even on the First Series Landranger in the same way.

Maybe a copyright trap? It's exactly the sort of thing that wouldn't cause any problems with navigation.
Steven

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Truvelo
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Re: OS One Inch - misalignment on A859

Post by Truvelo »

I have found when redrawing my highway plans layer that many 1:50000 scale maps have such errors. That's why I prefer 1:25000/1:10000/1:2500 scale maps as they have fewer such faults. I'm not sure if it's a deliberate copyright trap but the smaller the scale more likely these errors are likely to exist.
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Re: OS One Inch - misalignment on A859

Post by ikcdab »

Truvelo wrote: Mon Apr 18, 2022 16:59 I have found when redrawing my highway plans layer that many 1:50000 scale maps have such errors. That's why I prefer 1:25000/1:10000/1:2500 scale maps as they have fewer such faults. I'm not sure if it's a deliberate copyright trap but the smaller the scale more likely these errors are likely to exist.
Not really errors, but cartographic adjustment to fit everything in on the smaller scales. At a large scale everything can be pretty much drawn exactly as it is in real life. As you get smaller, this is increasingly difficult to do and distortions begin to creep in for the of making things clear.
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