USERS MANUAL
NR300
REVISION
D
DATE
8/16/21
Page #:
9 of 48
www.novuspower.com
When a third satellite is detected and a range determined, a third sphere
intersects the area formed by the other two. This intersection occurs at just two
points. A fourth satellite is then used to synchronize the receiver clock to the
satellite clocks.
In practice, just four satellite measurements are sufficient for the receiver to
determine a position, as one of the two points will be totally unreasonable
(possibly many kilometers out into space). This assumes the satellite and
receiver timing to be identical. In reality, when the receiver compares the
incoming signal with its own internal copy of the code and clock, the two will no
longer be synchronized. Timing error in the satellite clocks, the receiver, and
other anomalies mean that the measurement of the signal transit time is in error.
This, effectively, is a constant for all satellites since each measurement is made
simultaneously on parallel tracking channels. Because of this, the resulting
ranges calculated are known as “pseudo-ranges”.
To overcome these errors, the receiver then matches or “skews” its own code to
become synchronous with the satellite signal. This is repeated for all satellites in
turn, thus measuring the relative transit times of individual signals. By accurately
knowing all satellite positions and measuring the signal transit times, the user’s
position can be accurately determined.
