[OSM-talk] (magical?) road detector

Ido Omer Ido.Omer at microsoft.com
Sun Feb 6 19:40:35 GMT 2011

Hi Steve,

What we currently exposed is a web service that given two points finds the best road between them (or at least what it considers as best, which can be really bad sometimes)
We are not stopping people from using this service in their editors and achieve part of the functionality you suggested (we really hope this will happen).
We will add more functionality with time and are open to suggestions.


-----Original Message-----
From: Steve Bennett [mailto:stevagewp at gmail.com] 
Sent: Sunday, February 06, 2011 2:19 AM
To: Thibault North
Cc: talk at openstreetmap.org
Subject: Re: [OSM-talk] (magical?) road detector

On Sun, Feb 6, 2011 at 1:01 PM, Thibault North <tnorth at fedoraproject.org> wrote:
> In the mapping process (with JOSM or such tool), following roads is 
> not really a problem, especially when they are not too sinuous (and 
> that's when the road detector works well...). It can be done in a few 
> clicks. Maybe the tool should try and act differently (but that is 
> more GUI/UI related), and we could imagine the following scenario:
> - The user wants to map roads and selects a "road extraction" tool.
> - He roughly follows a road, maintaining a click (as you would do to 
> paint with a brush in image processing softwares)
> - The algorithm knows the approximate path, and tries to fit exactly 
> the center of the road.

I think this would be the best way to do it. If an editor could perform each of the following operations with a single click or
- draw straight way segment from the last node to the mouse cursor
- draw from the last node to the mouse cursor, following a perceived road
- undo last automatically drawn section

Or perhaps even the following:
- advance from the last node a further X distance, following roads (where X is dependent on zoom level)

...then you have the makings of a very efficient process for tracing roads off imagery. The last operation above would let you keep hitting a key to advance a road until something goes wrong, then backtrack and fix it manually.

What I saw in my testing was that most of the time (perhaps 70%) it got the road right, and sometimes it was just hopelessly wrong. That is presumably because the algorithm is determined that there *is* a road to find. It would be better for it to give up and not draw a road at all if its confidence isn't high.


talk mailing list
talk at openstreetmap.org

More information about the talk mailing list