AGS107 Study Guide - Final Guide: Scatter Plot, Central Tendency, Analysis Of Variance
Topic 1:
GPS = global positioning system
- 24 NAVSTAR satellites (made by the american military)
- Geostationary satellites (set above a specific location at all times)
- Orbital satellites: used in GPS
- 18000km above the earth surface
- Orbit the earth twice a day
- 5 ground stations monitor the satellites
GPS receivers and satellites:
- GPS receivers need to be in a line of sight
- They communicate via a frequency- each satellite has a unique signature code
(wavelength of 19 cm )
- Signal travels at the speed of light (3.0 X 108 m/s)
- GPS receiver sends back the same signature that it receives and calculates how much
(time period) the signature is out of sync
- Course acquisition code C/A (chunky and less accurate)
- Carrier phase code, L1and L2 (more accurate)
istance from satellite to receiver speed of light ime dif f erence of signal syncD = × T
Atomic clock - based on the pendulum swing of an atom
- Very expensive
- Only in satellites
- Very accurate clock
Summary:
1. Turn GPS on
2. Locate satellites in its line of sight
3. GPS downloads the almanac from each satellite and synchronizes its clock with the
satellite
4. GPS mimics the satellites signature code
5. GPS measures the time difference in the code and gives a location.
Topic 2:
Four satellites are needed to find a GPS location.
The more satellites the more accurate the location, the process is known as triangulation or
trilateration.
- HDOP= horizontal dilution of precision
- VDOP= vertical dilution of precision
- PDOP= positional dilution of precision (combination of both horizontal and vertical
dilution)
- Satellites in only 1 or 2 quadrants = poor horizontal dilution or High HDOP
- Satellites in less than 10-15o above the horizon = poor vertical solution or High HDOP
Document Summary
24 navstar satellites (made by the american military) Geostationary satellites (set above a specific location at all times) Gps receivers need to be in a line of sight. They communicate via a frequency- each satellite has a unique signature code (wavelength of 19 cm ) Signal travels at the speed of light (3. 0 x 10 8 m/s) Gps receiver sends back the same signature that it receives and calculates how much (time period) the signature is out of sync. Course acquisition code c/a (chunky and less accurate) Carrier phase code, l1and l2 (more accurate) istance from satellite to receiver. Atomic clock - based on the pendulum swing of an atom speed of light. Four satellites are needed to find a gps location. The more satellites the more accurate the location, the process is known as triangulation or trilateration. Pdop= positional dilution of precision (combination of both horizontal and vertical dilution)
