Error analysis for the Global Positioning System: Difference between revisions

Revision as of 13:13, 5 June 2021

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== Multipath effects ==

GPS signals can also be affected by [[multipath interference|multipath]] issues, where the radio signals reflect off surrounding terrain; buildings, canyon walls, hard ground, etc. These delayed signals cause measurement errors that are different for each type of GPS signal due to its dependency on the wavelength.<ref>[http://www.navipedia.net/index.php/Multipath Navipedia: Multipath]]{{deadlink|date=June 2021}}</ref>

A variety of techniques, most notably narrow correlator spacing, have been developed to mitigate multipath errors. For long delay multipath, the receiver itself can recognize the wayward signal and discard it. To address shorter delay multipath from the signal reflecting off the ground, specialized antennas (e.g., a [[choke ring antenna]]) may be used to reduce the signal power as received by the antenna. Short delay reflections are harder to filter out because they interfere with the true signal, causing effects almost indistinguishable from routine fluctuations in atmospheric delay.