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

2. 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, km, 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

3. GPS Errors and Dilutions
Troposphere
Lower level of the atmosphere
Variations in temperature, pressure, and humidity will created errors in
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.

4. 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

5. 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

6. 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