 |
 |
Dear Advani et al,
Forgive me if I'm missing something, but it sounds as though the basic thing you're trying to do is to "snap" points (the GPS points for vehicle locations) to lines (a road network.)
It's no great surprise that you're finding that the vehicle location GPS points don’t precisely align with the road network. GPS data is inherently "noisy" and needs to be cleaned before being used. "Snapping" is one such kind of cleaning.
If you're using ArcMap, you'll find a tool called "Snap" in the "Editing Toolbox" under "Arc Toolbox" that performs this operation.
If you're using QGIS, there is a "Snap Points to Lines" tool under the "SAGA Tools" in the "Processing" Toolbox which should perform the same kind of operation.
One closing note: Even after snapping, your data may require further cleaning – perhaps manual editing/cleaning. Be sure to examine the results of the snapping operation! As mentioned above, GPS data is inherently “noisy.” Consequently, you may find that some points snapped to a different route than the one you expected because they were sufficiently “off” to be closer to another route than the one you expected. These will need to either be discarded or manually snapped you the route you had in mind – if you can figure out where the relevant point might be. Sometimes GPS point data is simply sufficiently “off” that individual data points have to be discarded.
Hope this helps.
Best regards,
Ben
Benjamin Krepp | Chief GIS Programmer/Analyst
CENTRAL TRANSPORTATION PLANNING STAFF
857.702.3670 | [log in to unmask]
-----Original Message-----
From: Northeast Arc Users Group [mailto:[log in to unmask]] On Behalf Of Chris Duncan, GISmatters
Sent: Tuesday, June 4, 2019 8:58 AM
To: [log in to unmask]
Subject: Re: Develop path using coordinates in GIS
Maybe others with more experience will come to your rescue, but I am not
aware of any tool that will automagically recognize "incorrect" points
and fix them... how could the tool possibly discriminate b/n good and
bad points? I think your only options are:
* manually detect these glitches (either before or after route-matching)
and edit the source points (e.g., interactively in your GIS) to move bad
points onto what you believe is the correct route
* create a reduced street network for OSRM -- if you know the trips of
interest followed certain routes, you can select just those routes
(e.g., select by road class) and save to a new network and feed that
reduced network to OSRM
As for converting point sequences into lines, there are tools for that:
QGIS: Points2One plugin (install as needed), among other options
ArcGIS data management toolbox PointsToLine
These tools let you optionally create separate routes for groups of
points based on some attribute field of the point data, and optionally
control the order in which the points are sorted to create the line.
Chris
On 6/3/19 10:49 PM, Chintan Advani wrote:
> Hi Chris,
>
> Thank you for your response. You got it right that I am using point
> samples of a vehicle's travel to estimate the most likely path it
> actually followed along a road network. I have tried using ORSM tools
> earlier. The path would have been accurate if my co-ordinates were
> exactly on the road network. However, the data set that I have posses,
> has the co-ordinates that are slightly away from the road network at
> several locations. The figure attached with the mail shows the stated
> problem. The vehicle should have taken a straight path as can be seen
> that it follows a straight route. However, the two co-ordinates in the
> paths are drifted away from the road network that leads to an
> unrealistic movement for the vehicle. Hence, I need some tool that can
> adjust such drifted co-ordinates ( probably through some technique) as
> well as draw a path between all such points in a similar fashion as the
> existing ORSM tool does. And, in case there is no such tool that can do
> both, can you please suggest some method to overcome the problem?
>
> large scale network.PNG
> issue with ORSM.PNG
>
> Thanks and Regards,
> __________________________________________
> Advani Chintan Sanjeev
> Research Scholar,
> Civil Engineering and Build Environment,
> Queensland University of Technology,
> Brisbane-4000, Australia.
>
>
> On Tue, Jun 4, 2019 at 12:15 PM Chris Duncan, GISmatters
> <[log in to unmask] <mailto:[log in to unmask]>> wrote:
>
> Can you describe a bit more precisely what you wish to do? It sounds
> like perhaps you have point samples of a vehicle's travel and you want
> to estimate from those the most likely path it actually followed
> along a
> road network? If that's your aim, you need to familiarize yourself with
> the challenges and rewards of route-matching, e.g. using OSRM:
>
>
> It's been a few years since I worked with this stuff, but I think the
> general approach is still reasonably well presented in this paper by
> some of the early researchers:
>
>
> You don't have to master that material to use OSRM, but it's good to
> understand some of the challenges involved in what is a more or less
> constrained estimation (educated-guessing) problem whose success
> depends
> on the quality (density, accuracy, and precision) of your point data.
>
> If you have some other goal in mind, please try to clarify.
>
> Chris
>
> On 6/3/19 9:55 PM, Chintan Advani wrote:
> > Hi guys,
> >
> > I am looking for some tools in ARCGIS/ QGIS that can help me to
> plot the
> > trajectories using the lat/long coordinates for different
> vehicles. It
> > would be great if someone can suggest some inbuilt tools as I am
> new to
> > this these software and need some guidance. I even tried to
> install a
> > map-matching python script based tools from some online source but
> > facing issues during execution. I can even share the sample data
> if that
> > can be helpful.
> >
> > Thank you in anticipation.
> >
> > __________________________________________
> > Advani Chintan Sanjeev
> > Research Scholar,
> > Civil Engineering and Build Environment,
> > Queensland University of Technology,
> > Brisbane-4000, Australia.
> >
> -------------------------------------------------------------------------
> This
> > list (NEARC-L) is an unmoderated discussion list for all NEARC Users.
> >
> > If you no longer wish to receive e-mail from this list, you can
> remove
> >
>
> --
>
> Chris Duncan, Ph.D.
> President, GISmatters
> [log in to unmask] <mailto:[log in to unmask]>
>
>
> Tel: +1 413.549.2052
> Fax: +1 413.658.0346
>
> 1 Tuckerman Ln
> Amherst, MA 01002
>
--
Chris Duncan, Ph.D.
President, GISmatters
Tel: +1 413.549.2052
Fax: +1 413.658.0346
1 Tuckerman Ln
Amherst, MA 01002
------------------------------------------------------------------------- This list (NEARC-L) is an unmoderated discussion list for all NEARC Users.
If you no longer wish to receive e-mail from this list, you can remove yourself by going to http://s.uconn.edu/nearcsubscribe.
Please be advised that the Massachusetts Secretary of State considers e-mail to be a public record, and therefore subject to the Massachusetts Public Records Law, M.G.L. c. 66 § 10. ------------------------------------------------------------------------- This list (NEARC-L) is an unmoderated discussion list for all NEARC Users.If you no longer wish to receive e-mail from this list, you can remove yourself by going to http://s.uconn.edu/nearcsubscribe.
If you no longer wish to receive e-mail from this list, you can remove yourself by going to http://s.uconn.edu/nearcsubscribe.
