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

[Andy Robinson]

Nick Whitelegg wrote:
>Sent: 30 October 2006 12:16 PM
>To: talk at openstreetmap.org
>Subject: Re: [OSM-talk] Freemap-NPE: OSM + New Popular Edition Mashup
>
>>>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.
>
>That seems to be the case in my experience too. In the default area
>(Fernhurst, Sussex) the paths seem to be exactly where they should be. In
>some places in Cheshire, they're slightly off.
>
>I wonder if it would be possible to take the rectification shifts gathered
>from the GPX tracing application and store them in a database, so that the
>corrections could be applied per sheet?
>

Or better still have users able to calibrate individual grid boxes (as per
the gpx tracing stuff) and use that to collect rectification information.
Since I assume that the error occurs within the sheet and that the edges of
the sheet are presumably correct.

Cheers

Andy 

Andy Robinson
Andy_J_Robinson at blueyonder.co.uk


>Nick
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