Should I replace my GPS with my Cell Phone?

By Casey J. McLaughlin

Casey’s Take Homes:

  • Cell phones combine GPS (Global Position System) with other location technologies.
  • There are Multiple ways of determining location.
  • Date use determines requirements (accuracy and precision).

Inside a Washington D.C. metro station by C.McLaughlin (2012)

Walking around Washington D.C. recently, I thought to myself, this is just like walking in the woods!   No really, I made the connection because I was trying to use GPS navigation and not having great luck (it could be my service but I am also illustrating a point here).   Cities and forests both contain tall objects that obscure those magical satellites.  Now my phone IS smart and does not rely solely on GPS satellites but also calculates my location using cell towers and Wi-Fi base stations.  The precision is more than enough to navigate around the city.

I have been quite happy with my cell phone’s ability to map and find locations – new to me this summer.  I successfully got where I wanted to go using the default mapping application (Google Maps).  I easily found nearby museums and restaurants.  It helped me enjoy an unfamiliar city.  I have begun using the location tools on my phone for more than just getting directions – I now keep track of time, distance, and route of my runs and have started geo-tagging family photographs.  Who knew mobile technology would be so fun!

This post is not about extolling my new found enjoyment of having a smart phone (yes, I’m late to the party) but rather I’m thinking about the usefulness of cell phone locations for various work-related purposes.  At EPA, we follow, as best we can, specific data collection and documentation methods.  For example, every latitude/longitude point should be maintained to six significant digits.  Each point also has a horizontal collection method such as “Address Matching – House Number” or “GPS” or “Photo Interpretation.”  Now, this is partially because the official guidance needs updating (or is in process already).  The point here is not the details of what is IN the specification but rather what is NOT.  Cell phones, because they use a combination of techniques return a value for which we cannot easily determine precision or accuracy.

What is precision and accuracy?

Back to my cell phone, I guess I have two problems.  I do not know how well my phone is locating a position and since I do not know the methods, I am unsure how I should properly document the location.  Neither of these really diminishes the intrinsic value of using a phone for location, but EPA has more rigid documentation burdens that make using a phone for location more difficult.

I can use my cell phone for determining location, but I cannot replace my GPS because I am unsure I can document it sufficiently….yet. Is this an apps problem, a device problem, or a method problem?

Casey McLaughlin is a first generation Geospatial Enthusiast who has worked with EPA since 2003 as a contractor and now as the Regional GIS Lead. He currently holds the rank of #1 GISer in EPA Region 7′s Environmental Services Division.

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