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Should I replace my GPS with my Cell Phone?

2012 October 15

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.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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13 Responses leave one →
  1. Kevin Lynch permalink
    October 30, 2012

    I think it’s more of an app issue. In Texas, the TCEQ also has similar requirements to document how our data points were collected. For our field work we use Trimble GPS units and post-process the points using Pathfinder Office. When I export the GPS data the exported shapefile contains the pertinent data required by the TCEQ for each point collected.

    There are apps that show the GPS status on Smartphones, although I don’t know if any provide a means for you to record the pertinent GPS metadata when you take a location fix. If there isn’t I would image someone enterprising app developer could come up with one. The newer smartphones have great GPS chips that can read not only the US GPS constellation but the GLONASS satellites as well. My new phone gets a fix much faster and does better even while I’m indoors than my old smartphone did.

  2. Wesley permalink
    October 31, 2012

    One vital component missing in this blog; that’s the fact that your phone provided location (GNSS or otherwise) will never provide better accruacy than +/- (approx. on a good day) 3m. At the end of the day it will really boil down to the business requirements and they will determine the device which is to be used.

  3. Greg Overtoom permalink
    October 31, 2012

    We’re starting to look at this issue for our field staff as we look to implement iPhones and iPads for field use. These devices cannot meet our current locational accuracy standards, but the low cost and high functionality of these devices compared to our dedicated GPS receivers is making us reevaluate our standards.

    Personally, I rely almost totally on my cellphone for geolocational activities now, but I’ve seen enough problems in routing and run tracking (usually lost signal in remote areas) to keep me from wholesale switching away from a dedicated GPS device.

  4. cmclau02 permalink*
    October 31, 2012

    Great comments! I think the technology is there, or near enough that the next part of the conversation may be about applications recording and reporting the quality of their locational data. We are getting more and more spatial data and maintaining it for use and re-use, in my opinion, is heavily dependent on knowing the quality. I have been dealing with this issue since graduate school where we were collating locations of biological specimens written about in journals and trying to map them — which become very challenging when dealing with location descriptions such as “about a mile from Sandy Point.” We captured the data as a point and gave it an accuracy rating. Imagine getting this point without any idea that it is a +/- 1 mile and I can imagine the problems this could create when lumped in with higher quality data. (Yes, I realize critters move about so spatial accuracy of any one specimen being collected is more dependent on the samplers’ path of sampling than it is on the specimen but I am illustrating a point about spatial accuracy here!)

    Bottom line remains, we are close but not quite there. I don’t want my field people going out with their cell phones and collecting data quite yet.

  5. jrobicha permalink*
    October 31, 2012

    Good points all…I know I talk about it all the time…data quality objectives, or as Wesley put it business requirements…in most instances we do need that precision and accuracy. But just because its my nature to be contrarian, Casey how much would have cell phone GPSs helped five or so years ago during the chemical fire response when responders were calling data back with cross streets that weren’t on maps?

  6. Casey McLaughlin permalink*
    October 31, 2012

    Emergency Response always has different requirements and is always focused on getting the best actionable intelligence as quickly as possible. This is the same principle that is prevalent right now in mobile apps because “about here” is enough actionable information for the follow-up question of “what is around here.” Perhaps coming from the government where we have so many procedures and polices is a bit different, which I willingly cede. The point is (har-har) still getting information ABOUT the point (and how it was collected) can and should be factored when someone actually uses the point later on.

  7. cmclau02 permalink*
    December 11, 2012

    Interesting and relevant article about battery life. I didn’t read the actual paper so I’ll just include a link to —

  8. Alan Ladde permalink
    January 9, 2013

    So, faced with the choice:
    1. More accurate, but unable to document how much more accurate, or
    2. Less accurate with metadata to confirm exactly how inaccurate it is,
    which would you personally choose?
    Which does bureaucracy force you to choose?

  9. cmclau02 permalink*
    January 9, 2013

    It partially depends on the situation but personally I would choose knowing the accuracy. Its easy to improve and troubleshoot known accuracy limitations but too often I’ve dealt with the unknown. Usually the mapmakers gets the blame, not the people acquiring the data — they’re job is long finished. The bureaucracy forces me to accept whatever I can get and use whatever is available. Our central data set that we use is populated in multiple ways by multiple entities with multiple purposes — see more at Where is that Facility

  10. Regy bulner permalink
    January 18, 2013

    Can you tell me about GPS app for iPad ?

    • cmclau02 permalink*
      January 22, 2013

      I’m sorry, I really don’t know much about the iPad or any GPS apps. Please post back if you find something useful!

  11. Casey McLaughlin permalink*
    April 30, 2013

    The cell phone vs GPS location topic will be revisited for awhile and here is another post from Directions Magazine and includes links to some congressional testimony from a cybersecurity researcher.

  12. Casey McLaughlin permalink*
    September 13, 2013

    More on this topic from an ESRI post…
    “Smartphones, Tablets and GPS Accuracy”

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