You are here

Use GPS Maps to improve map databases, but protect privacy

Mapping programs, and fancy GPSs come with map databases that will, among other things, plot routes for you and estimate the time to travel them. That's great, but they are often wrong in a number of ways. Sometimes the streets are wrong (missing, really just a trail, etc.) and they just do a rough estimation of travel time.

Yet all the information is there, being collected constantly by every car that drives the roads with a GPS. Aggregating this data will tell you what roads are real, what roads might be missing, which are one-way, where freeway entrances and exists really are.

And it will also tell you real-world speed examples at various times and dates, at rush hour or otherwise. Even a range of speeds so you can know the speeds for faster and slower drivers and get a really good estimate of your own likely speed on a given road at a given time. After removing the anomalies (like people stopping for coffee) of course.

Rental cars with GPSs are collecting this all the time (sometimes to nefarious uses, like charging whopping fees for brief trips out of state). Technically this data can be had.

But here's the bad part -- there is a potential for giant privacy troubles unless this is done very well, and some may be impossible to do without a privacy risk. After all, until you upload the data, there is clearly a log of your travels sitting there to be used against you. Only a system with rapid upload (and which discards data that gets old, even if it's not uploaded) would not create a large risk of something coming back to haunt you.

The data would have to be anonymized, of course, and that's harder than it sounds. After all, your GPS logs say a lot about you even without your name. Most would identify where you live, though that can be mitigated by breaking them up into anonymized fragments to a degree. Likewise they'll identify where you work or shop or who you visit, all of which could be traced back to you.

So here's the Solve This aspect of this problem. Getting good data would be really handy. So how do we do it without creating a surveillance nightmare?


Hey Brad, This is from someone of your ClariNet days now transported to the midwest. What a bizarre coincidence that I just happen upon your post of GPS map making from user data. Several times at ClariNet we stumbled on the same idea. If you check my web page you might get the clue that I do a lot of navigating with GPS and real-time navigating on my laptop, plus handheld. And I do this where map data is old and often wrong (who cares, except we crazy geodashers, about a random place in Kansas where a bridge is out). Anyway I have long been interested in a colloborative project for not only collecting tracklogs for mapping, but ideally even close enough to real-time to do things like detect construction delays or road closures and such. Obviously a baseline of unimpeded data could generate an average speed, per time of day, per day of week, for stretches of road, so that even just a few tracklogs showing a one or two sigma deviation would indicate a likely problem. As to mapping itself I had done a personal project just to determine if in fact anyone knows exactly where interstate highways are. Now, if that isn't known (and it isn't, precisely or widely) then imagine how hard it is to get data on county roads in South Dakota. Anyway if you're really into this, drop me a line as I might not happen back here.

The other neat thing to consider, given how WAAS was retrofitted into earlier GPS standard, is that satellite broadcasting of critical driving info (weather, road status) in burst mode for the entire of north america, repeated with any updates on continuous basis, can be picked out by the GPSr that definitely knows where you are, but also with a programmed route knows where you're going and so therefore the relevant data from the broadcast can be buffered up and then displayed to the traveler. Here in the midwest where weather can change by the minute and by the mile and be life-threatening, all the existing information channels are hopelessly inadequate. The world is so biased toward point-to-point, on-demand info (sorry, the net isn't going to reach nowhere South Dakota any time soon and that's where this is needed) that broadcast gets ignored, but somehow people need to put GPS and filtering broadcast in the same idea and they might see a whole great new opportunity.

Actually there are a number of ideas one quickly gets when one drives about 10,000 miles in the middle of nowhere looking for random places.

douq millar (variation on the real one)

Yeah, I thought about this long ago too after my first GPS roadtrip and blogged it because I haven't yet see it happen. Drop me your real E-mail Doug, by mailing me. ( will work with a challenge)

Brad - I run a portable GPSr in the car everytime I go anywhere and love the accuracy and the way it allows me to worry about other things than "where and when is the next turn". I have recently reviewed the tracklog and find it tells lots about my habits.

It's mine and I control it -- and if I were worried about the privacy aspect would simply turn off logging. For me, I can see more "good" uses (when was I where) than bad uses (yes, officer I was speeding, and my GPSr will prove it).

I wonder how cognizant the police would be about using a person's GPSr as a forensic tool.

I see a day not too far out where cell phones and "active" GPSr will be more closely coupled with the cell data updating traffic conditions in to the "routing" software. I recently started using the "detour" feature of my unit and it has saved me considerable time when needed.


There are far, far more cell phone driving down the road than cars with GPSr and the cell phone companies can already infer traffic patterns from tower usage. Last year I worked in the same building with a company that was working on dynamic routing around traffic jams using cell phone data.

Yup, that's another one of my old ideas (a decade ago I imagined the cell company even calling you to warn you about the traffic jam ahead as a for-pay service, wasn't able to interest anybody though.)

However, the GPS data, especially with WWAS, should be more accurate, and was tracking location accurately long before the E911 mandate pushed for this in cell phones.

While there are more cell phones, at least in densely populated areas, check South Dakota some time for coverage, the spatial resolution is way lower. For instance, on divided roads direction matters, not just that you're somewhere within a certain segment. Certainly which loop of an interchange is way below the resolution of cellphone tracking. So in short I'm not sure how much usage data can be acquired this way, certainly not much for mapping and routing.

One thing that this technology could be used for in a positive way is to track down wreckless drivers and serial speeders on the freeway. This could enable police departments to institute a automatic ticket issuing system where it can use the GPS in most GSM cell phones to locate your home and send a ticket for your speeding to your home address. This will greatly improve safty of law enforcement officials, since they never know what you are going to do when they pull you over.

Um, that's exactly the sort of thing I was trying to stop it being used for. People don't want to buy stuff that reports them to the police. Innocent people don't want to buy stuff that reports them to the police. Stuff I buy should work in my interests, not somebody else's.

Are you saying your a wreckless, serial speeder! The revelations! First, you have pornogrophy on your website, availiable to minors without even the most simple age verification system - some of this pornogrophy violates house bill #2257 - and now you sound like your defending criminals??? May god have mercy on you.

With enough cars participating you wouldn't need continuous data. Maybe a minute a day. Send with no identification, just the GPS coordinates. The unit should be smart enough to only send the minute of data when the car is in transit and has had a few minutes of travel on either side of the minute window.

The unit could also have regions defined as high density areas and those that aren't. The ones that aren't could be sent days later because that data is more for verifying roads than for immediate traffic information.

> Yet all the information is there, being collected constantly by every
> car that drives the roads with a GPS. Aggregating this data will tell
> you what roads are real, what roads might be missing, which are
> one-way, where freeway entrances and exists really are.
> [...]

Hi Brad.

Did/do you implemented a system, that aggregates GPS data and creates a map? And is it done automatically? I'm interested, because we are developping thus a program. If you have ideas or experiences in this topic you are welcome to post a comment on our site.

Greetings, Björn

Add new comment

Subscribe to Comments for "Use GPS Maps to improve map databases, but protect privacy"