How does a smartphone GPS compare to a standalone satellite GPS?

Generally the specialized GPS units are better because in America they will also use the WAAS system. WAAS stands for Wide Area Augmentation System. It is a series of ground based reference points that contain GPS receivers and transmitters. Because the reference points are sessile their positions in GPS coordinates are highly accurate. They receive the GPS signals from the satellites, use it to calculate their own position which produces and error based on erroneous positions of the satellites. Errors can be introduced because satellites orbit in a small figure eight, atomshperic distortion of the timing signals, etc. The WAAS reerence points calculate the error and use the transmitter to send a correction to mass WAAS stations that then calculate all errors and send a deviation correction to WAAS geostationary satellites which then broadcast the correction to any WAAS enabled receiver. The receiver of the WASS correction then uses it as a way to produce an even more accurate psoition. With my dedicated GPS receiver ( a Delorme PN-60) with WAAS turned on and fully synchronized the unit is accurate to about 3 meters. When I'm in open ground with no covering trees or buildings, I find I can drop a penny and return later to find the position of the penny to within about 1m. Assisted GPS (A-GPS) uses the GPS positioning system and the location of cell phone towers and WiFi access points (WAPs) to reach an accuracy of about 8 meters which is what most cell phones use. For WiFi is measures the signal coming from WAPs and how strong the signal is received. This gives an indication of how close to the WAP the phone is an it uses multiple WAPs to triangulate. Using GPS + WiFi + cell towers gets the 8 meters. Using only WifI + tower only gets about 74m, and cell towers only gets around 600m of accuracy. If you want the science you can find it here: http://onlinelibrary.wiley.com/doi/10.1111/j.1467-9671.2009.01152.x/abstract

To summarize : In the middle of nowhere, with no 3G or 4G cell signal (including A-GPS), you will not see a difference between cellphone and handheld GPS performance (it will always take several minutes to acquire several GPS satellites, including cancelling the intentional drift introduced by DoD).  However, anywhere you get a 3G cell tower signal with Assisted GPS, the cellphone should achieve an almost instant lock, in just a second or two, because the cell tower provides an A-GPS broadcast that contains information about all the satellite frequencies/codes in use in the region (so the searcher in the cellphone can try a small (5-10) number of frequencies/codes very very fast.) This is why handheld standalone GPS devices are going the way of the dinosaur ... They are hopelessly slow (2 mins) compared to A-GPS (2 secs).

Keeping it simple.... When everything required in available(Outdoor, network, GRPS for locking and maps, battery backup) the smartphone GPS does the same as the standalone one... in fact it can be flexible in application with lots of apps to choose. Otherwise, smartphone is a piece of junk. SS GPS always works  (outdoors of course) but the application and features is limited and optimised to the device(car navigator, pocket navigation etc).

http://shivanshchaudhary.wordpress.com/2014/04/05/the-death-of-gps-in-india-coming-soon/