GPS Satellite Surveying, 4th Edition

6.5 Ambiguity Fixing

Ambiguity fixing is essential for achieving centimeter-level accuracy in relative positioning. We first discuss ambiguity fixing in the context of a constrained adjustment, provide a brief background on the various approaches proposed to solve the ambiguity fixing problem, and then discuss in detail the popular LAMBDA method. In the second part of this section, the view is broadened by looking at practices in related disciplines to solve similar problems that might also be of benefit in certain circumstances when applied to GNSS applications.

6.5.1 The Constraint Solution

Fixing ambiguities implies converting real-valued ambiguity estimates to integers. The procedures follow the general linear hypothesis testing as described in Section 2.7.3. The objective is to constrain the estimated ambiguities of the float solution to integers. Let's assume that the parameters are grouped as

6.5.1

The symbol denotes the estimated station coordinates and possibly other parameters, such as tropospheric refraction or receiver clock errors. The symbol denotes the estimated float ambiguities. Using the same partitioning, other relevant matrices from the float solution are