I remember when GPS was only available in the 10lb size that fit in a backpack. I also remember when GPS was all but useless without post-processing for differential correction. How times have changed.  We all take for granted now that GPS will be in the smartphones that have become our lifeline, but even that is relatively new. When we first started researching phones to create ourGeoJot+ app, not all cellphones were smartphones and not all smartphones had GPS chips. However, we knew a change was coming. By September 11. 2012, all wireless service providers in the US were going to be required to supply precise location information for 9-1-1 calls.

So most people have taken for granted that their smartphones have GPS for the last couple of years. And the more people used it, the more it became a selling point for phones and the more it was refined. Many cell phones now, such as the Samsung Galaxy S6 or the iPhone6 have both GPS and A-GPS. A-GPS (Assisted GPS) uses cell phone towers is often used when you first start up your GPS because it has faster fix times. It also may work better inside buildings or in urban canyons (when there are a lot of tall building). GPS is a satellite-based navigation system developed by the US government. This GPS option on a cell phone uses the satellite signals and does not need cell phone towers. While it tends to use more battery power, it also tends to yield more accurate locations outside of urban areas.

In the past few years, additional satellite system have become available to general public. Many phones can now use GLONASS satellites. GLONASS is similar to GPS but is operated by the Russian Government. Recently some phones have even started picking up satellites from the Chinese satellite system that is currently being refined.


3-5 meter accuracy is now the standard for any hardware that boasts GPS capabilities. And the more sophisticated standalone GPS units such as those from Juniper and Trimble can now offer < 1 meter accuracy in real time without post-processing and centimeter accuracy post processed. It makes you wonder … what’s next? Cost does vary with accuracy which also should make you wonder, what accuracy do I really need for my project?