GPS Tracking ROI

“You can observe a lot by watching”, was allegedly said by Lawrence Peter “Yogi” Berra … who also offers the disclaimer,  I didn’t really say everything I said”.  No matter who said it, it’s sort of an interesting truism.  I’ve been “watching” this GPS business for a lot of years now and I have observed that even though the technology itself is somewhat complex there are an awful lot of players in the game who try to make it more complicated than it really is … as least in the terms that an end user rather than a PhD needs to understand it.

I went searching a few minutes ago for a good definition of TTFF (Total Time to First Fix).  This is one of those esoteric parameters of the GPS overall system and the particular receiver being used that is ever so important to the way the system will actually serve the customer that it is very surprising to me that it isn’t prominently displayed in every GPS receiver’s operating specs.  Yet it is often hidden deep within an “acronym soup” or worse yet, not specified at all.

When a brand new GPS receiver is turned on for the very first time … a “factory cold start” the receiver has absolutely no idea where in space it is located.  It knows in general terms, known as the almanac data set where each satellite should be, but this data is really only a shortcut method to minimize the data each satellite must broadcast and is nowhere near accurate enough to perform a fix with.  The receiver must busily begin “listening” for signals from the GPS satellites in space and when it finds one it extracts the ephemeris data from that satellite’s navigation signal and then goes on to the next and the next and the next until it has at least 4 “good” sets of data to begin actual calculations with.  Ephemeris is a $1.49 word that means, in GPS terms, a table that shows the difference in the position of the individual satellite from the “perfect orbit” position the satellite would be in if no errors or distortions in its orbit had occurred.

There is a very good description of ephemeris and the compumetric gymnastics a GPS receiver must go through from power on to first accurate fix here at www.pocketgpsworld.com.

Sadly I do not see data for the common commercially available commercial tracking systems.  A worthy project this would be indeed, because, as you can see from PocketGPS World’s personal handheld unit tables there is a tremendous variation in usability illustrated by the vast differences in time to first fixes for the different industry offerings.

If you decide to try GPS tracking on your business’s vehicles you should certainly demand that the proposed vendor give you an actual on-vehicle demonstration and be very careful to see that the units you are thinking of buying ‘come on line” in a time that will make them useful.  In particular, test the performance after the vehicles have been shut down overnight, or better yet, over a weekend out of service.  The differences in performance may astound you.

I’ve seen many systems that take so long to attain their first fix after a vehicle starts that the vehicle may already be shut down again at its first stop before an accurate fix takes place, making the whole exercise in tracking location and speed for business ROI futile, at best.