MATLAB Code for GPS "Availability" Analysis

When evaluating Global Positioning System (GPS) performance, availability serves as a critical metric that reflects the system's capability to meet accuracy requirements at specific times and locations. Using MATLAB's algorithm simulation tools, we can efficiently model how factors like GPS signal coverage, satellite geometry distribution, and environmental interference affect availability.

The implementation approach typically follows three steps: First, establish a satellite orbit model to simulate the spatiotemporal distribution of visible satellites using functions like ephemeris or orbital mechanics toolboxes. Second, calculate Dilution of Precision (DOP) values based on receiver position through matrix operations on satellite-receiver geometry, where lower DOP values indicate better positioning conditions. Finally, combine constraints like signal-to-noise ratio thresholds to statistically determine the percentage of time meeting positioning requirements, which defines availability.

In extended applications, you can incorporate additional error sources such as multipath effects and atmospheric delays using error modeling functions, or compare joint availability improvements across different constellations (like GPS and BeiDou) through constellation simulation algorithms. Such simulations provide quantitative foundations for ground augmentation system deployment and receiver algorithm optimization.