[talk-ph] Automatic road tracing from satellite imagery?
Eugene Alvin Villar
seav80 at gmail.com
Sat Feb 5 03:39:24 GMT 2011
I've tried it and it's a hit and miss. In some places it worked perfectly.
In another place it's like a drunk driver who ignores roads. Hehehe.
Merkaartor plans to incorporate this tool, experimentally, in the near
future. I'm sure some JOSM person is also creating a plug-in for this since
this tool's API is extremely simple.
Here's an email by the Microsoft researcher who helped create the tool to
the main OSM mailing list:
> I am a researcher at Microsoft and I am currently working on the road
> I joined a bit late and can’t post answers in the existing road detector
> thread, but I might be able to provide some additional info regarding the
> road detector.
> It is **FAR** from being perfect, but in our experiments it may produce a
> lot of value (== save time) if you use it correctly. When use it correctly
> means don’t expect too much, so here are some practical tips:
> 1. It is currently uses the two end points as example and tries to
> find a path that is similar to those examples, so it is recommended to use
> the tool at a zoom level that will let you make sure you click on a road and
> not near a road (we will probably loosen that restriction in the future).
> 2. Don’t try to challenge the detector too much, it will probably
> fail, instead if you have a very complicated winding road break it into a
> few sections and let it detect shorter legs (it will still save you most of
> the clicks…)
> 3. One of the main features used is color, so if the road changes
> its color a lot, break it again into shorter legs.
> 4. We currently only compute one path (road) between the points and
> cannot provide a meaningful score for that path. Defining a score is a
> difficult problem (but we are open to ideas…).
> 5. To speed things up, we are using a bounding box that is in many
> cases smaller than the bounding box provided by the client (we take constant
> margins around the bounding box defined by the two end points). This means
> that if you click on the two end points of a U shaped road we might truncate
> the lower part of the U and find a “shortcut “ through buildings, fields,
> etc. And again you’ll need to break the query into shorter legs… (I am
> currently working on speeding things up and I hope to get rid of this
> limitation in a week)
> 6. The algorithm is currently ignoring junctions, but I should be
> able to add them very soon (early next week)
> That is for road detection. The other mode we will provide is road
> exploration which will enable finding all the roads in a certain bounding
> box (well, you’ll probably need to click once or twice…) I am not sure if
> there is an exposed version of this service (I hope not, since so far it is
> really a bunch of experiments…) but we should have it really soon (a week or
> two). For the road exploration we will probably have some kind of certainty
> level for each road segment.
> I will be very happy to hear of any complaints/requests/places where you
> think the detector should work but it fails/any other feedback.
On Fri, Feb 4, 2011 at 10:19 AM, maning sambale <emmanuel.sambale at gmail.com>
> Not yet useful. I tested both the silverlight and openlayers demo. I
> can't create a nice road trace both for straight grids and curvy
> baguio type roads. Since the algorithm depends on imagery color, I
> think tracing quality will depend on the image contrast, which varies
> for different areas.
> It would be nice if the app can manipulate the base imagery like
> setting image contrast to highlight the roads before tracing.
> Once the basic code/api is released by Bing, I'm sure osm-geeks can
> develop the algorithm much better. ;)
> On Fri, Feb 4, 2011 at 8:40 AM, Eugene Alvin Villar <seav80 at gmail.com>
>> Here's something somebody whipped up to play around with things:
>> On Fri, Feb 4, 2011 at 8:37 AM, George Tujan <gtujan at gmail.com> wrote:
>>> now that's pretty cool!
>>> On Fri, Feb 4, 2011 at 2:23 AM, Eugene Alvin Villar <seav80 at gmail.com>
>>>> See this blog post:
>>>> And this YouTube video:
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