Explain the concept of leveraging multi-antenna or multiple GNSS constellations.

• A. Only increases hardware cost.
• B. Reduces geometry.
• C. Of little use in practice.
• D. More satellites and constellations improve geometry, observability, redundancy, and robustness to outages, reducing PDOP/GDOP.

Answer: (D)

More satellites from multiple GNSS constellations give you a wider, more evenly spread view of the sky. This improves geometry, lowering dilution of precision values like PDOP and GDOP, which leads to more accurate position estimates and faster, more reliable fixes. With more observations from different systems, the receiver can better resolve unknowns such as receiver clock bias and navigation ambiguities, improving observability. Redundancy increases too—if one satellite or system is blocked or degraded, others keep the solution valid, enhancing robustness to outages. Adding a multi-antenna setup provides spatial diversity, aiding attitude determination, multipath mitigation, and further improving accuracy and reliability. In short, leveraging more satellites and constellations directly enhances accuracy, reliability, and availability.