The code is from https://geodesy.noaa.gov/gps-toolbox/ZDcycleslip.htm
A MATLAB software package for GPS cycle-slip processing is presented in this paper. It realizes cycle-slip detection and repair in the measurement domain for GPS L1 and L2 signals. The software implements several classic approaches oriented to real-time processing. With the graphic user interface, the user can configure the raw data, set algorithm-related parameters, add synthetic cycle-slips, and view the detection results in both text and illustrated forms. In this paper, the theoretical background of the cycle-slip processing is introduced first. After that, the advantages and limitations of each implemented approach are identified. Finally, the functionalities of the software are briefly explained.