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In this article I will detail how I use GPS Data to answer questions about cell phone signal inadequacy in Arizona using all of our data collected in August.


We have a large municipal customer who commands some respect from AT&T and is able to actually ask them to put up new cell phone towers in certain areas which are lacking.

They track a large number of vehicles using our GPS Tracking product, and asked us if we could help them determine the worst cell coverage areas in Arizona, based on our customers’ data.

Since we track several thousand vehicles in Arizona, we were able to do this.

Above is shown a real-time location of all several thousand vehicles we track in the Arizona and San Diego area.

I took the data from August so far and compared the track time with the time we received the data, where the “lag” is due to cell signal being unavailable.

We pulled 2500 points ranked by longest to shortest lag, where the shortest lag was 6 minutes — bear in mind our updates occur in 2 minute intervals and typically take 5 seconds to make it from the tracking device and another 10 seconds to be processed and pushed down to your map.

I plotted these lagged position updates and color and height coded them based on how long they took to ultimately get forwarded.

This shows all places where there was some level of poor cell coverage in Arizona for August:

Thankfully, when comparing where the vehicles we track are, relative to where the “dead spots” are, they are not very troublesome, and do not cover where most of our drivers tend to be:

Then we can place it in a 3-D view where the height of the lagged positions indicates how bad that coverage is (e.g. how long the vehicle was out of range after it collected that point):


Then I can pull both a Cingular/AT&T Coverage image I prepared (from their website) and overlay it with Arizona. This map is not 100% accurate, and there are a lot of T-Mobile and partner network areas where our product works which are NOT depicted, but it gives a good idea of where our coverage is (it follows the roads and major metro areas typically. Note the edges are not exactly aligned since our mapping knows about curvature of the earth but the Cingular map does not:

Zooming down we see that the worst area of coverage is not “orange” (which indicates areas AT&T claims to work in):

Zooming down on this area, we see it’s a desolate road leading to a mine:

Looking at the data points relative to the aerial photo, we see how accurate our GPS Track is. Then we can zoom WAY down and see the exact areas of the mine which are being driven in.

So if I was Cingular, I wouldn’t worry about covering this remote mine, but I would worry about coverage where I pointed out with 2 arrows below, and perhaps place or adjust the cell tower there.

Knowing there are around 800 square miles in all of Arizona where our typical vehicles (e.g. forgetting about the mining vehicles) go out of range for more than 5 minutes is great to know, since there are 111,500 square miles in Arizona.

This means we are out of range less than 1% of the time. Since most GPS tracking products (ours included) store this data until the vehicles return to coverage, there is never any data lost. We store roughly 45 days of typical driving, so if a vehicle goes down into Mexico (where we do not currently have service) and back, we still will be able to show the exact locations they were at, if they were speeding, etc, once they return.

One of our customers drives back & forth to Mexico and is currently using our service to include our polygon geofences in order to ensure compliance with Federal law, and to check their times spent at the border (which helps them in their business due to certain reporting requirements). I will cover this company and their unique usage of the GPS Insight product in the future.