Thinking about the reliability of GPS

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Posted in: Corey


As the lead developer of Serval Maps, a collaborative mapping application, I rely on GPS to provide geographic coordinate information. My new project, which builds on the past work of Serval Maps, also relies on GPS.

This afternoon I realised that GPS isn’t as reliable as I first thought. I always knew that there were accuracy issues, especially with the cheaper GPS receivers in mobile phones. I also new that AGPS can have significant issues when there is no Internet connection available, especially as Serval Maps is designed to be infrastructure independent.

I also knew that GPS signals can be blocked, but what I hadn’t realised until this afternoon is that GPS signals can also be faked. This TEDx talk by Todd Humphreys illustrates how he was able to fake GPS signals. Coincidentally I saw the talk on the same day that I saw this Wired article.

Even as Serval Maps aims to be infrastructure independent it has always been reliant on the GPS capability of the phone to provide geographic location information.

I don’t have the luxury of time to think more about it at the moment, but I suspect the Serval Mesh could be used to distribute additional information that could be used to assist in the defence of this type of issue. Especially with the new encryption capabilities coming in the next release. In this way you could potentially have additional information from a trusted source that you could use to verify the geographic location information.

It is something to ponder if nothing else.

The photo of the GPS satellite was sourced from Wikipedia and is considered to be in the public domain.


This post was originally published on the Thoughts by Techxplorer blog and is licensed using a Creative Commons license.

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