vault backup: 2023-03-28 12:04:42

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 
+- Applies Trilateration for computing location In 2D (3 Circles) 
-
+- Applies Trilateration for computing location In 3D (4 Spheres) 
-GPS - Receiver 
+- But our receiver does not have an atomic clock!! 
-- 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!

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)
+
+

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