Derive Road Lines from GPS Points

[Gregory Yetman]

Hi,

We have a collection of GPS points collected from vehicles. The data
include date/time stamps, so it's pretty easy to construct linear
features from the data by stringing the points into continuous lines.
Many of the roads have been driven two or three times, so we would like
to average the tracks where appropriate to get better tracks. The catch
is that some of the GPS points have additional data that we would like
to preserve (such as change in surface type).

I was thinking that the following steps would be appropriate:

1. Separate the points by device and date collected. Our data provider
is sending them as one large file but with unique GPS device IDs, so
this is straightforward.

2. String the points together into lines based on the time of
collection. Insert breaks whenever the gap in time is too large.

3. Attribute the line features using the GPS points as events. As we
have many points (generally every second) the points will have to be
subset into suitable intervals. The points with changes in road surface
will be preserved, of course. The attribution could be done by splitting
the lines at the GPS points and assigning attributes based on location,
or we could build routes with events.

4. Where particular roads have been driven more than once, create a new
line geometry that is the average of the tracks. Transfer the attributes
of the previously created tracks to the new average lines.

I have a few questions before we start trying to automate this process.

First, does the above approach seem like a good way to tackle the task
so that we can preserve the attributes and get the best road geometry
possible out of the GPS data?

Second, I am least certain about what kind of functions are available
and their pros and cons for averaging lines (step 4 above). Does anyone
have advice on this?

Lastly, does anyone have pointers to scripts for automating this, or any
relevant papers that document this kind of approach?

We mostly work in ArcGIS (scripting in python and the like) but are
willing to pipe the data through other packages where it makes sense.

Thanks,

Greg

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Gregory Yetman
Senior Staff Associate
Center for International Earth Science Information Network (CIESIN)
Columbia University
URL: http://www.ciesin.columbia.edu/
e-mail: gyetman (at) ciesin.columbia.edu
tel: [phone]
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