Question

In GNSS positioning, the cycle slips are the most detrimental for estimating ________.

• A. Integer ambiguity
• B. Receiver clock error
• C. Multipath error
• D. Atmospheric delay

Hint:

Recall that the carrier phase integer ambiguity is defined as a constant whole number of cycles for an unbroken tracking arc, and think about what happens to that count when the receiver briefly loses and reacquires lock.

Answer 1

The Correct Option is A

Step 1: Understand the carrier phase observation.
In GNSS carrier phase positioning, the receiver measures the fractional part of the carrier phase and keeps a running count of the number of complete wavelength cycles \(N\) since it locked onto a satellite signal. This integer count \(N\) is the integer ambiguity, because at the moment of signal lock the receiver has no way of knowing exactly how many whole cycles lie between the satellite and the receiver, it can only measure the fractional phase.

Step 2: Define a cycle slip.
A cycle slip is a sudden discontinuity of a whole number of cycles in the receiver's continuously tracked carrier phase, most often caused by a brief loss of phase lock from signal obstruction, high receiver dynamics, low signal to noise ratio, or severe ionospheric scintillation. When lock is briefly lost and then reacquired, the internal cycle counter can jump by an integer amount, so the value of \(N\) held after the slip is no longer the true, constant integer that existed before the slip.

Step 3: Link the slip to ambiguity estimation.
Centimeter level carrier phase positioning depends on resolving \(N\) as one fixed integer over a continuous, unbroken tracking arc. The entire strength of the carrier phase method comes from treating \(N\) as constant so it can be estimated together with the receiver coordinates using many epochs of data. A cycle slip breaks this continuity, since the old integer no longer applies after the jump, and unless the slip is detected and repaired, or a new ambiguity is estimated, every position computed from that corrupted phase is offset by the slipped number of cycles multiplied by the wavelength, which can be a decimeter to several meters of error.

Step 4: Eliminate the remaining options.
Receiver clock error is common to every tracked satellite and is solved for as a single nuisance parameter in the position solution, it does not disturb the phase cycle count. Multipath error is a slowly varying bias caused by reflected signal paths, it does not create an integer cycle jump. Atmospheric delay from the ionosphere and troposphere changes smoothly with elevation and time, it is modeled or estimated as a continuous quantity, not a discontinuous jump. None of these three directly corrupts the integer ambiguity term the way a cycle slip does.

Step 5: Conclusion.
Because a cycle slip directly corrupts the integer ambiguity \(N\) that carrier phase positioning depends on being constant, it is the error type most detrimental to estimating the integer ambiguity.

\[ \boxed{\text{Integer ambiguity}} \]