I agree. The tracking function is independent from the presentation function.
For those who aren’t familiar, in a general sense gps is not too terribly different from cell tower pings. Both are based on the exchange of time-stamped signals between two devices with synchronized clocks. Add the speed of light and you can calculate how far apart the two devices are from each other.
If the gps antenna in your phone or vehicle has line of sight to one satellite, it places the device somewhere along a circle. If two satellites are visible the device is at one of two potential locations — where the circles for each satellite intersect. With three satellites, a specific point on the circle is identified — the circles for each of the three satellites will intersect in just one point. With four satellites elevation can also be calculated. (You need three satellites to map a point in two-dimensional space and four to map a point in three-dimensional space.) Additional satellites beyond four basically just improve the accuracy of the calculated location.
Because gps satellites are constantly moving in orbit around the earth, position accuracy can vary as they move in and out of range/visibility of the gps device. In mountainous areas, the landscape can obstruct some satellite signals if the device is in a valley or canyon, etc. At least until that satellite moves into view again (or a new one becomes visible). Accuracy is usually best under wide-open sky where the max number of satellites are visible at any given time.
What I don’t know is how much positional data a device or vehicle buffers before it either needs to be uploaded to the cloud or is overwritten by new data. But storage is cheap these days and the data is alphanumeric. So I expect it could be quite a lot. Anyone?
All of the above is MOO and my understanding only.
Great explanation.
I have a hand held portable GPS navigation device so I got to learn a little bit about how it works.
I agree that you need your unit (or vehicle) to be able to find and locate at least 3 different satellites in order for the GPS unit to know your exact location.
When I first turn on my GPS unit, it immediately starts to scan for satellites and it does take a bit for it to lock onto 3 of them.
The important point which you also mentioned is there are some locations (usually heavy tree cover) where it just spins and spins and never finds 3 satellites until I move a little bit to a better clearing. Its important to note that this seldom happens as I usually get a lock-on even if tree cover seems dense. Its only happened on a couple occasions where I had to move to a more clearer view of the sky.
To help answer your last part, and if we are mainly talking about the hardware GPS modules that a vehicle would have without any real interface to a full navigation system, but the vehicle has the GPS module hardware in the vehicle, my understanding is
the storage of last location points and the frequency is limited based on the capacity of the GPS module hardware that the vehicle has. So it can be different for different types of vehicles.
I found this article below and they refer to that type of GPS module as a "data logger" only type module. This is the type of GPS module we are mainly talking about when the vehicle has nothing installed other than the factory GPS module that is usually installed nowadays on vehicles which allows it to be further tapped into with a full navigation system later.
The companies put in the basic module so its easy to have add-on navigation options later if a customer wants it. Some things are cheaper on the assembly line to get the initial basics installed, so they do certain things for all vehicles. There are other reasons they put in the basic module too like having accident information that manufacturers wanted so they have some information to protect them from liability.
The basic GPS module hardware will find and store positions based on its storage capacity within the module itself because it has nowhere else to put it.
Once a vehicle or GPS Navigation system has a full Data Logger, Data Pusher, and/or Data Puller as part of its features (like a phone), then the GPS data points can be stored externally which would have much more storage capacity.
Below is an article that can help understand it.
"Types of GPS tracking devices
We can broadly divide GPS tracking devices into three categories based on their primary functions -
- Data loggers
- Data pushers
- Data pullers
"Data loggers record location in routine intervals and save the information in the device’s internal memory. Some cameras use data logging to display the location like where the photo was taken at, and data loggers can be used to track vehicles as well.
Data pushers are the most common GPS tracking units & are commonly known as “GPS beacons.” Rather than saving the location data on internal memory as data loggers do, data pushers send and store the information on the server. This means the storage space of the information is not as limited as for the data loggers.
Data pullers are the last type of GPS trackers, and they are also called GPS transponders. The data puller GPS does not send location updates at routine intervals, but instead, you have to request the data from it. This type of GPS is sometimes found in computers or for items where the location does not need to be known constantly."
GPS Tracker - The Ultimate Guide (In - depth analysis)