This paper introduces development of the MATLAB GUI based simulation tool to generate GPS measurements which are similar to the measurements of commercial GPS receiver. There are many open source softwares in order to model GPS error components. However, most of softwares have focused on evaluating integrity monitoring algorithm and availability test. On the other hand, accuracy is relatively unimportance and simply calculate GPS residual error assuming Gaussian distribution model. Therefore, these softwares have limits to produce accurate GPS receiver measurements. The purpose of our simulation tool is to generate GPS measurements anytime and anywhere on the basis of GPS error components of particular user accurately and efficiently. The simulation tool include two program modes to calculate independent error components for GPS. One is precise generating mode using past measurement data such as SP3, IONEX, and weather information. The other is real time generating mode applying results of individual GPS error model. Consequently, L1/L2 pseudorange, and L1/L2 carrier phase measurements are produced using GPS errors that are calculated by designated program mode. The GPS measurement results of the simulation tool were verified reliability using received GPS data in real environment and were demonstrated resemblance between the two. All evaluated results can be shown from GUI display mode, and GPS measurements are changed into RINEX format for the purpose of analyzing in commercial GPS data process program. This simulation tool is useful to perform simulation for various GPS augmentation systems, and plans to expand generating multi-constellation GNSS measurements.

Keywords: GPS simulation tool, GPS measurements, GPS error source modeling