When using GPS, how many theoretical...

Question 1 of 31048sAF8fzPmHh84Hs4YT96y

When using GPS, how many theoretical position lines are required for a three-dimensional fix?

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Question 1 of 31048

Q

When using GPS, how many theoretical position lines are required for a three-dimensional fix?

🔍 Key Concepts

• 3-dimensional (3D) position vs. 2D (latitude/longitude only) • How many unknowns must be solved for in GPS positioning (including receiver clock error)? • Difference between a satellite range line and a traditional visual LOP (line of position)

💭 Think About

• If you want a 3D fix (latitude, longitude, and altitude), how many separate unknowns are you solving for? Then ask yourself if the GPS receiver has any additional unknown error to solve. • Compare: for a 2D fix with visual bearings, how many LOPs are typically used? How does adding another dimension (height) change the count? • Think about each satellite giving you a range (distance). How many separate ranges do you need to intersect in order to solve for all the unknowns?

✅ Before You Answer

• Be clear on whether the question is asking about 3D position (including height) or only lat/long. • Remember that GPS must correct for the receiver’s clock error as an additional unknown. • Verify that the number you choose is at least equal to the number of independent unknowns the system has to solve for.