Unit 2 Unmanned Aircraft Module 1 The UAS Component 1.5 – GPS Errors and Dilutions

GPS Errors and Dilutions Ionosphere GPS calculations are based on signal traveling through the vacuum of space Signal has to reach a receiver on earth If signal does not pass through a complete vacuum then it cannot make contact, causing error The upper layer of the atmosphere, 50-500km, is called the ionosphere Consists of charged partials, and free electrons that can effect the GPS signal Disruptions lead to timing errors, many errors can be accounted for using mathematical modeling The majority of GPS errors are due to the ionosphere

GPS Errors and Dilutions Troposphere Lower level of the atmosphere Variations in temperature, pressure, and humidity will created errors in 107.19 Remote Pilot in Command A remote pilot in command must be designated before or during the flight of the small unmanned aircraft. The remote pilot in command is directly responsible for and is the final authority as to the operation of the small unmanned aircraft system. The remote pilot in command must ensure that the small unmanned aircraft will pose no undue hazard to other people, other aircraft, or other property in the event of a loss of control of the aircraft for any reason. The remote pilot in command must ensure that the small UAS operation complies with all applicable regulation of this chapter. The remote pilot in command must have the ability to direct the small unmanned aircraft to ensure compliance with the applicable provisions of this chapter.

GPS Errors and Dilutions Multipath Errors When GPS antennas receive incorrect signals May have bounced off buildings, trees, and ground objects GPS must be able to distinguish from reflected signals and direct ones Mask angle is used to correct for this Antennas only receive signals from 15º or higher off the horizon

GPS Errors and Dilutions Satellite Clock Used to calculate the position of the receiver on the earth Must be highly accurate, slightest time differences can mean hundreds of miles of error Satellites circle at high rates of speed, this causes relativity to come into play Relativity causes the clocks to offset, causing error Satellites must be monitored and updated to the correct time

GPS Errors and Dilutions Ephemeris In the information sent to the receiver, the satellite includes projected position of the satellite orbit Position is used to calculate range Receivers looking ate different angles to other satellites, creating different ranges The predicted orbit can cause error called ephemeris error