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9 Cards in this Set
- Front
- Back
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What does GNSS stand for? How does it differ from GPS? |
Global Navigation Satellite Systems -> the name for any network of Satellites. GPS is the North American GNSS network. GNSS is the broader term for the North American GPS, the Russian GLONASS, and the EU’s GALILEO |
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What is the minimum number of satellite needed for an accurate positional location? |
You need at least 4 satellites to find your location on the earth |
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What two key types of information are sent by GNSS satellites to receivers that allow for the determining of position? |
The time it takes for light to travel from the satellite to the receiver → information on distance and time |
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Explain the causes of two different types of dilution of position error and how those errors can be minimized. |
PDOP: Position dilution of precision: depends on satellite configuration, if they’re all stacked on top of each other, you have a higher dilution of precision = low accuracy Can also be caused by obstructions - Horizontal dilution of position - Vertical dilution of position |
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How is distance from a GNSS satellite to a receiver measured? |
Using the speed of light to calculate distances. Combining the distances and satellite locations, the receiver can find the latitude, longitude and height. |
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What type of error is caused by GNSS signals bouncing off of objects near a receiver? |
Effect of clock errors. Clocks in the satellites have to be precise and the clocks in receivers are synchronized with those satellites. |
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How does assisted GPS differ from differential GPS? |
A-GPS: Improves startup performance (time) of a GNSS receiver by using the cellular network towers. Differential GNSS: Can increase accuracy. Requires additional receiver in known position. |
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What spatial errors could you expect with a phone based GPS? |
3-15m, 95% of the time (clear view of sky) |
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When will GPS not work? |
Tunnels, inside buildings, dense forest, under water, under ground. AKA whenever the signal from satellite cannot be received. |
