Error modeled using afwa prism model database and

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Degrees South 154.30578 Degrees East 20 Dual Frequency Horizontal Error 15 Single Frequency Horizontal Error 10 - Five degree mask angle - Sampled every minute over 24 hour sample interval - 80 cm (1σ) receiver noise - No tropo or multipath Summary Statistics 5 Dual Frequency Horizontal Error: 3.4 meters (95%) 0 Single Frequency Horizontal Error: 19.2 meters (95%) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time of Day (Hours UTC) Figure A-5-17. Example Worst Site Single-Frequency Horizontal Performance Page A-34 October 2001 GPS SPS Performance Standard Comparison Comparison of All-in-View Single and Dual-Frequency Vertical Errors Worst Single-Frequency Performance Location, 8 June 2000 LOCAL MIDNIGHT 70 ANALYSIS NOTES Vertical Error (meters) 60 - Worst Location on 8 June 2000 for All-in-View Solution: 50 20 Degrees South 154.30578 Degrees East 40 Dual Frequency Vertical Error 30 Single Frequency Vertical Error 20 - Five degree mask angle - Sampled every minute over 24 hour sample interval - 80 cm (1σ) receiver noise - No tropo or multipath Summary Statistics Dual Frequency Vertical Error: 6.2 meters (95%) 10 Single Frequency Vertical Error: 39.3 meters (95%) 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time of Day (Hours UTC) Figure A-5-18. Example Worst Site Single-Frequency Vertical Performance The most significant features of the error plots to note are the significant jumps in error approximately five hours before local midnight, and fact that horizontal error jumped along with vertical error. Horizontal error increases occurred in concert with the rapid appearance of a gradient in electron density over the region associated with the worst-case location. In general, position solution errors increase not necessarily due to increases in electron density, but to gradients in the electron density above a given location that causes wide variations in single-frequency delay for all satellites used in the position solution. The other effect of gradients in electron density is to change significantly the distribution characteristics of GPS errors. In a two-frequency position solution, RMS vertical errors are generally about 50% larger than RMS horizontal errors below a latitude of 55°, and two to three times larger at the poles. For single-frequency position solutions, RMS vertical errors can be over six times worse than RMS horizontal errors within 20° of the geomagnetic equator. Due to the effect of electron density gradients, the ratio of east and north errors for the singlefrequency position solution in an East-North-Up (ENU) coordinate system can also be impacted. In a dual-frequency position solution, RMS east and RMS north errors are approximately equivalent at the equator and the poles, and RMS east errors are generally 20% smaller than RMS north errors at mid-latitudes. For a single-frequency solution, RMS east errors can be 50% smaller than RMS north errors within 20° of the geomagnetic equa...
View Full Document

This document was uploaded on 09/26/2013.

Ask a homework question - tutors are online