Welcome back to #blockchainmygps!

One of the more prominent FAQs I hear is “Why does my #gps take so long to get a position”?

Anyone who has used a #gps receiver knows that when it’s turned on, it could take from 30 to 60 seconds to calculate a position. In this “instant everything” world of ours, who has the patience to wait that long? In this blog post, I will be explaining the reasons why and what can be done about it.

In order for a #gps receiver to calculate a position, it needs to know exactly where the satellites are in space. A #gps receiver knows exactly where the satellites are by downloading a fairly complicated message broadcast from each satellite in view. Each of these messages contain something called an #ephemeris which is a fancy way of saying “I am satellite A, here is where I am at time X”. Unfortunately, these messages are broadcast at a very slow rate of 50 bps (bit per second), this translates to about 30 seconds or more for the #gps receiver to receive these signals.

To make it worse, for a #gps receiver to calculate a position, it needs #ephemeris data from 4 different satellites. Hence, depending on the environment, the total time to receive all 4 #ephemeris can take much longer than 30 seconds, if at all.

Since downloading broadcast #ephemeris takes so long, is there a way to get around it? Luckily, the answer is “Yes”.

#extendedephemeris technology is a way of predicting the location of the satellites for the near future, hence, the word “extended”. By comparison, broadcast #ephemeris is typically valid for 2 to 4 hours, whereas the state-of-the-art #extendedephemeris technology can be used for up to 28 days. By knowing the exact location of the satellites for the next 28 days, a #gps receiver can totally skip downloading the broadcast #ephemeris and progress directly to calculating the position as soon as the receiver is turned on. The net result of using #extendedephemeris is that instead of taking 30 to 60 seconds to get a position, a typical receiver will now take 1 to 2 seconds to get the job done.

Now you know why #gps takes so long to get a position and what #ephemeris / #extendedephemeris are, my next blog post will talk about how #ultralowpowergps receiver technology can get around these problems.