Hardware biases and their impact on GNSS positioning

Sammanfattning: GNSS hardware biases appear in code and phase observations, and originates both from the receiver and satellite hardware. These biases influence the accuracy in precise GNSS positioning if not handled properly.This thesis is based on two papers, where one is a review paper published in GPS Solutions, and the other is a research paper currently in review (resubmitted after minor revision) for Journal of Geodetic Science. The first paper compiles current results and gives an overview of those situations where biases are of the greatest importance for precise positioning. The second paper investigates the satellite dependency in two cases of relative phase biases.In the first paper, a review is given on how hardware biases influence precise GNSS positioning in various situations. These can roughly be divided into five cases: positioning not employing the ionosphere free combination to which the satellite clock corrections are aligned, GNSS based ionospheric modeling, determination of the phase ambiguity as an integer in PPP, and positioning with GLONASS.In the second paper, the satellite dependency for two cases of relative phase biases are investigated: relative between-receiver biases in single differenced phase observations from two receivers, relative between-signals biases in observation differences between two signals recorded by the same receiver and associated with the same carrier frequency. In both these cases a satellite dependency was discovered. The first case showed a difference of 0.8 mm between the greatest and smallest values, while the corresponding difference in the second case was 3.5 mm.It was also discovered that the biases in the first case varied periodically over time, and with a period of one sidereal day. The exact cause for these variations could however not be determined in the experiment, even though multipath could be excluded as their source.