[Openstreetmap] New Popular Edition map scans
Ronan Oger
ronan at roasp.com
Sun Dec 19 10:44:06 GMT 2004
Hi,
I may have algorithms together for raster-vector xforms of images that may
work for stuff like ordonance survey.
One downer with raster-t-vector xforms, however, is that the raster images
strip out contextual content and break like segments turhough overlays that
expert systems like our brains detect as overlays but that state machines
like CPUS do not detect. Hence for example, a word with a line between two
letters is broken into two words (ignoring the fact that most of the time the
text is also rendered as paths...
However, with some post-processing, it is possible to take some raster images
and generate reasonable vectorized maps that can be a lot smaller and less
prone to pixel noise.
Also, injecting GPS data into the map via statistical methods can/could also
re-inject context such as stiching line segments back into a single trace and
assigning it to a transport layer and providing a speed based on travel speed
on the GPS trace...
I know that this si a lot of if/could/should/may handwaving, but that's mostly
because nobody's taken the time to try it out.
I've played a bit with rasterising using autotrace
http://www.roitsystems.com/autotrace and with my own hand-cooked tracing
algorithms, and am convinced that something vectorially useful and compact
can be extracted from map data such as what ordonance survey gives out.
Ronan
On Thursday 16 December 2004 23.12, Richard Fairhurst wrote:
>Hi all,
>
>For those who are interested, I've now got my collection of Ordnance
>Survey New Popular Edition maps scanned (1in to the mile, c. 1950,
>complete coverage of England and Wales).
>
>The scans look wonderful... as I guess they should with a total size of
>25GB! I'm currently working on compressing them further, and hope to
>have a CD ready at the start of the New Year.
>
>Until then, I've posted a brief excerpt on my blog:
>http://www.systemeD.net/blog
>
>cheers
>Richard
>
>
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>
>
--
Ronan Oger
http://www.roasp.com
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