[OSM-talk] Freemap-NPE: OSM + New Popular Edition Mashup

[Andy Robinson]

Tom Chance wrote:
>Sent: 30 October 2006 10:50 AM
>To: Nick Whitelegg
>Cc: talk at openstreetmap.org
>Subject: Re: [OSM-talk] Freemap-NPE: OSM + New Popular Edition Mashup
>
>> Would like to announce the first prototype of a project to overlay OSM
>> footpath data on the New Popular Edition maps from npemap.org.uk,
>> codenamed "Freemap NPE".
>
>Great idea! One note of interest:
>http://nick.dev.openstreetmap.org/openpaths/index.php?e=476000&n=175000
>
>These paths to the North East of Reading should lie either side of the
>River Thames, but instead one seems to be in the river and the other some
>distance away from it. Which layer needs budging over here? The OSM data
>should be accurate given that I cycled down each path, twice per side.
>

I think the problem is with the rectification of the npe mapping. I found
for a sheet I wanted to do a gpx trace over that the calibration error was
83m in one direction. You can see basically the same issue on the link you
gave in that you can see the gridline on the far right tiles are a little
way inside the edge of the display area. Zoom right in and you will find the
left right shift error matches very well with the error seen at your two
footpaths.

Cheers

Andy


>Kind regards,
>Tom
>
>
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