ArcGIS Server - compare routes

Question

I've got a list of points, and a route that an external provider has generated through those points.

I would like to generate a route using those same point with my own road network.

Then I want to be able to detect if there is any significant difference between the two routes.

One suggestion is that for the 2 routes, we find out what road segments they travel across, and compare the list of road segments?

Is this a valid approach? How do we go about getting the list of road segments given a route?

I am using ArcGis server 9.3 with Java 5 and Oracle 10g. I am using the ST functions and NetworkAnalyst via the java api.

Thanks.

Answer 1

I've just implemented something similar in my application. I have a list of lat/long coordinates from a GPS device and needed to create a route based on this data.

I started by matching each GPS position with a node in my street network. I then removed 'consecutively duplicate' nodes to filter out those consecutive positions that are at the same node. Then, I started 'walking' through my street network, starting at the first node. I checked the first node and second node and checked for a common street segment. If I found one, great. If not, I create a shortest path between the 2 nodes and use those roads instead. I continue doing this until I've examined all the nodes. At the end of this process, I have a list of road segments that the vehicle traveled and the order in which they were traveled, too.

Unfortunately, I'm using a different map, different programming language, and different database. As such, sharing the code won't be helpful to you at all. Hopefully the process I described above will be enough help for you to accomplish your task.

Answer 2

Calculate the route using your points and road network. Then buffer the resulting route into a polygon (the buffer radius should be your "tolerance"). Then clip the external route using your polygon. If the resulting polyline is non-empty, then there is a deviation outside of your tolerance.

This method does not acount for any "significant" deviations such as backtracking, U-Turns, or taking a nearby parallel road.

Alternatively, you can compare the resulting "directions" and check for deviations there--particuarly using street names. This saves you from checking every road segment. If you have any deviations in road names, then check the individual road segments of each section.