GPS and AGPS – What they mean
To begin with, the basic definitions are GPS Global Positioning System & aGPS Assisted Global Positioning System. One is assisted, one isn’t.
We recommend you read about how gps works if you are unsure what GPS is.
How it is assisted
aGPS is assisted by the cellular network towers, which are always pulling & updating their GPS locations from orbiting satellites with their own built in GPS receivers.
With this cached location data, they can provide updates to aGPS enabled devices; such as phones, and some GPS Tracking Devices.
GPS is not assisted, so it relies on information pulled directly from satellites to provide location updates.
TTFF – Time To First Fix
Because GPS is pulling location updates directly from the orbiting satellites, rather than having a speedy helping hand from the cellular network, there can be delays if the orbiting satellites are not within close proximity, or line of sight.
The time in which it takes to lock onto multiple satellites to pinpoint where is called Time To First Fix, or commonly abbreviated as TTFF.
GPS TTFF can take anywhere from 30 seconds to a few minutes, depending on a variety of factors such as;
- Current location
- Location of satellites above
- Interference caused by weather
- Buildings, mountains or other signal wash out
Better line of sight = quicker TTFF
Benefits of aGPS over GPS
Apart from the above benefits of TTFF, being able to utilize the cellular network means that aGPS has the following benefits;
- Obtaining satellite location data quicker (TTFF)
- The device is using less processing power
- Decrease in battery usage
- Ability to obtain satellite location data indoors, where line of sight may not be optimal.
Benefits of GPS over aGPS
Whilst aGPS is faster in finding location data from satellites, GPS provides better accuracy. However, research has shown that the difference is negligible.
Another benefit of GPS is that there is no additional costs, unlike aGPS which will incur extra usage costs as mobile carriers consider it data usage.