diff --git a/content/notes/08-proximity sensors.md b/content/notes/08-proximity sensors.md index cecb0b639..95e8f3a21 100644 --- a/content/notes/08-proximity sensors.md +++ b/content/notes/08-proximity sensors.md @@ -181,47 +181,6 @@ GPS - Receiver GPS - Receiver - Uses messages received from satellites (n"4) to determine the satellite positions and time sent - Gives roughly distance to satellite -- Applies Trilateration for computing location In 2D (3 Circles) Dunedin - -GPS - Receiver -- Uses messages received from satellites (n"4) to determine the satellite positions and time sent -- Gives roughly distance to satellite -- Applies Trilateration for computing location In 2D (3 Circles) Dunedin - -GPS - Receiver -- Uses messages received from satellites (n"4) to determine the satellite positions and time sent -- Gives roughly distance to satellite -- Applies Trilateration for computing location In 2D (3 Circles) Dunedin - -GPS - Receiver -- Uses messages received from satellites (n"4) to determine the satellite positions and time sent -- Gives roughly distance to satellite -- Applies Trilateration for computing location In 3D (4 Spheres) Dunedin - -GPS - Receiver -- Uses messages received from satellites (n"4) to determine the satellite positions and time sent -- Gives roughly distance to satellite -- Applies Trilateration for computing location In 3D (4 Spheres) Dunedin - -GPS - Receiver -- Uses messages received from satellites (n"4) to determine the satellite positions and time sent -- Gives roughly distance to satellite -- Applies Trilateration for computing location In 3D (4 Spheres) Dunedin But our receiver does not have an atomic clock!! - -GPS - Receiver -- Uses messages received from satellites (n≥4) to determine the satellite positions and time sent -- Gives roughly distance to satellite -- Applies Trilateration for computing location -- The receiver has four unknowns, the three components of GPS receiver position and the clock bias [x, y, z, b] -- Using four (or more) satellites, we can set up 4 linear equations to solve for x, y, z, b -- In some cases we know z or b we need less satellites! Urban Canyon -- Urban environment similar to a natural canyon -- Can impact radio reception of GPS receivers -- Buildings reflect and occlude satellite signals -- Reducing precision of positioning in urban environments -- Makes positioning impossible Urban Canyon -- Urban environment similar to a natural canyon -- Can impact radio reception of GPS receivers -- Buildings reflect and occlude satellite signals -- Reducing precision of positioning in urban environments -- Makes positioning impossible www.hci.otago.ac.nz The end! \ No newline at end of file +- Applies Trilateration for computing location In 2D (3 Circles) +- Applies Trilateration for computing location In 3D (4 Spheres) +- But our receiver does not have an atomic clock!! \ No newline at end of file diff --git a/content/notes/09-location-sensors-3.md b/content/notes/09-location-sensors-3.md new file mode 100644 index 000000000..13dc620c6 --- /dev/null +++ b/content/notes/09-location-sensors-3.md @@ -0,0 +1,78 @@ +--- +title: "09-location-sensors-3" +tags: +- lecture +- info305 +--- + +# Location Sensors - GPS (cont.) + +GPS - Receiver +- Uses messages received from satellites (n≥4) to determine the satellite positions and time sent +- Gives roughly distance to satellite +- Applies Trilateration for computing location +- The receiver has four unknowns, the three components of GPS receiver position and the clock bias [x, y, z, b] +- Using four (or more) satellites, we can set up 4 linear equations to solve for x, y, z, b +- In some cases we know z or b we need less satellites! Urban Canyon +- Urban environment similar to a natural canyon +- Can impact radio reception of GPS receivers +- Buildings reflect and occlude satellite signals +- Reducing precision of positioning in urban environments +- Makes positioning impossible + +Urban Canyon +- Urban environment similar to a natural canyon +- Can impact radio reception of GPS receivers +- Buildings reflect and occlude satellite signals +- Reducing precision of positioning in urban environments +- Makes positioning impossible www.hci.otago.ac.nz The end! +![Urban canyon](https://i.imgur.com/WgWREXs.png) +![Urban canyon](https://i.imgur.com/1aKMSLg.png) + +GPS - Problems +- Urban environment similar to a natural canyon + - Can impact radio reception of GPS receivers +- GPS will not work indoors +- GPS quickly kills your battery +- Accuracy strongly depends on antenna design and device form factor + - “Position tests by the mobile phone revealed a median error between 5.0 and 8.5m” + - “Increase by a factor of 2 to 3 compared to standalone GPS sensors.” + - “Very large errors are uncommon and rarely exceed 30m” +- Long startup time ( 30s - 12.5min needed for sending almanac) +- Several proposed improvements: AGPS, DGPS, RTKGPS + +> [!INFO] ^Depends on many parameters + +# Location Sensors - AGPS, DGPS, RTK GPS + +A(ssisted) GPS +- Introduced by Qualcomm in 2004, used extensively in mobile phones +- Idea: + - Traditional GPS only uses radio signals from satellites + - Assisted GPS (A-GPS) uses network information (transmission of almanac) + - Increase position accuracy by also incorporating Wi-Fi Positioning System and cell-site multilateration +- Advantages: + - Faster location acquisition + - Higher precision (with WiFi Positioning & cell-site multilateration) +- Disadvantages: + - Requires Internet connection + +![A(ssisted) GPS](https://i.imgur.com/u7iLeWG.png) + + +D(ifferential) GPS +- Enhancement to GPS to increase location accuracy and integrity +- DGPS correct errors using a stationary receiver station with a known location + - Stationary receiver knows own location and can calculate and Delta between known position and GPS position + - Stationary receiver broadcasts signal correction information (Delta) +- Standalone GPS provides ~15m accuracy +- DGPS can provide ~3-5m (and max. 10-15cm) accuracy +![D(ifferential) GPS](https://i.imgur.com/WCH4dJk.png) + +- Various DGPS networks implemented worldwide +- iBase VRS (New Zealand) (see also Trimble) +- DGPS & RTK GPS within NZ +- http://www.geosystems.co.nz/solutions/ ibase-vrs/ +![nz iBASE VRS](https://i.imgur.com/0yv7rWC.png) + + diff --git a/content/notes/info-305.md b/content/notes/info-305.md index 221d6135f..92533fd1c 100644 --- a/content/notes/info-305.md +++ b/content/notes/info-305.md @@ -22,6 +22,6 @@ tags: - [x] [[05-pervasive-ubiquitious-2]] - [x] [[06-challenges-for-ubicomp-and-intro-to-sensors]] - [x] [[07-location-sensors]] -- [[08-proximity sensors]] -- +- [x] [[08-proximity sensors]] +- [ ] [[09-location-sensors-3]] # Info \ No newline at end of file