Question

a.Among the 3 types of GPS receivers (GPS, DGPS, ArcGPS), which one is most and least accurate

b.What are 4 examples of parameters that you can measure with GPS?

Answer 1

(a) Most and least accurate GPS receiver:

• there are 3 types of GPS receiver,
  • GPS
  • DGPS   
  • ArcGPS
• DGPS (Differential Global Positioning Systems) is most accurate.
• GPS (Global Positioning Systems) receiver is less accurate because it is only able to get signals from 3 satellites ,for accurate result 4 satellite is required.

(b) Parameter measure with GPS:

• Distance
• Velocity
• position
• Relative Position – the Moving Base Solution
• Longitude, Latitude and Height position

• Distance:

  • GPS satellites are equipped with an atomic clock, which ensures timing stability to less than one-millionth of a second. By integrating Doppler-derived speed with this level of time signal reliability, an extraordinarily accurate distance measurement is achieved.

  • There are a number of tests which we have carried out over the years to verify and improve our measurement algorithms for applications in vehicle testing.

• Velocity:

  • The use of GPS in automotive testing is now well established, and Racelogic has been a market leader and innovator for over a decade. GPS systems have revolutionised the accuracy and convenience of testing, development, and validation within the industry.

  • 

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  • There is a common misconception that speed measured via GPS is done so as a function of position against time. If this were the case, GPS velocity would be just about unusable, because GPS position relies on precise measurements of the distance from the receiver to the satellite, and therefore suffers from numerous effects - such as atmospheric interference - which delays the signal.

  • Fortunately, velocity isn't measured like this: instead, the Doppler shift in the signals coming from the satellites is captured and this leads to an incredibly accurate measurement of speed.

• Position:

  • GPS positional accuracy is subject to ionospheric interference, which causes a satellite signal to change in length as it travels towards the Earth's surface. This means that, depending on the quality of the receiver, accuracy can vary by several metres.

• Relative Position – the Moving Base Solution:

  • In the field of automotive testing, and especially that of ADAS development, knowing the distance between moving vehicles is often a requirement.

  • This can be achieved on a test track by using multiple VBOX units and a Base Station, but the area over which testing can be conducted is determined by the range of the telemetry modems that broadcast correction messages.

  • 

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