Very cool Chris.
What technology are you using at the backend?
Is the source available under an open source license? (I don't need it
yet, but I'm busy trying to think up a good excuse to explore warping
further).
Christopher Schmidt wrote:
One of the things that I've been interested in for a while is an easy to
use map rectifier. There are a lot of maps -- historical maps
especially -- which are interesting on their own, but are far more
interesting if you mix them with other data. The reason I originally got
interested in this was for the idea of annotating OpenStreetMap
segments: take existing, out of copyright maps, georectify them against
known points, and use the resulting map to name streets. Obviously for
well-groomed areas of something like OpenStreetMap this would be of
limited benefit, but it does offer a new way for people who don't have a
GPS to contribute to poorly groomed or mapped areas of the OpenStreetMap
project.
However, most of the existing options suffer in a variety of ways. The
primary way in which they suffer is not even a technical problem, it's a
well understood social problem: high quality map data is not free. No
free data means that desktop applications don't have much they can do:
unless you're Google or Microsoft, you can't afford the amount of data
you need to georeference maps for the whole world.
Luckily, these days that data is made available from a number of
sources. Google Maps and Virtual Earth have moved into the realm of
providing free-to-view satellite data for the whole world, and that's
all you need for rectification. However, desktop applications like
GRASS and OSSIM don't have the ability to take advantage of this data:
the web nature of these tools makes taking advantage of them more
difficult for desktop applications, and there was no good way to use
these services to rectify a map.
As part of working for MetaCarta, one of the things I get to do is work
on services which end up on MetaCarta Labs[1]. People who were at
Where 2.0 probably remember seeing MetaCarta up on stage presenting some
of the technology we host on Labs for public use. Finding places where a
significant gap in the tools available to the community exists and making
them available is one of the things that some of my time gets spent on.
In an effort to help non-GIS professionals associate their images with
places in the real world, Schuyler Erle and I have developed a web-based
map rectification tool, which is available now for public use. The service
will allow you to upload an image, and using a reference map, you can
select ground control points -- points from the reference map which
match up to the uploaded image -- and then warp the image. You can use
any of a number of default base maps to reference against, or add your
own WMS or KaMap layers to the map and use them to find ground control
points.
The service is available from http://labs.metacarta.com/rectifier/ . You
can see that there have been a number of interesting maps uploaded.
We've tried to make a service which is generally useful, including
providing WMS URLs to the warped imagery, providing the imagery for
download as GeoTIFFs, and allowing users to comment on the maps you
upload.
I'm sure some of the people on this list have interesting maps that they
haven't had an oppourtunity to associate with the real world.
Personally, I've been having a lot of fun with the service:
georectifying imagery from MIT, from the 1930's to today, tourist maps
that I've taken snapshots of with a digital camera and uploading, and
historical maps from wikicommons.
I'm not sure who else has a need for this type of tool, but if you have
a map image and would like to use it inside your OpenLayers
applications, this is one way to get started: upload the image, warp it
to fit, and drop it into place. No need to set up a server. Click a few
buttons and go.
A quick getting started[2] guide is available, and I'd love to hear
feedback that anyone has on the service: what is broken, what is
missing, and what is nice about it. You can keep up with changes to the
service on the MetaCarta Labs weblog[3], which will mention any major
changes to the service.
Check it out. I'd love to hear any thoughts you might have.
Regards,
[1] http://labs.metacarta.com/
[2] http://labs.metacarta.com/rectifier/directions
[3] http://labs.metacarta.com/blog/
--
Cameron Shorter
http://cameron.shorter.net
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