From 5ee5f95fe45d85ef14a31f9b276dc3b67c476783 Mon Sep 17 00:00:00 2001 From: Jet Hughes Date: Tue, 21 Mar 2023 12:15:32 +1300 Subject: [PATCH] vault backup: 2023-03-21 12:15:32 --- content/notes/07-location-sensors.md | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/content/notes/07-location-sensors.md b/content/notes/07-location-sensors.md index f8b395bd4..d61a761e4 100644 --- a/content/notes/07-location-sensors.md +++ b/content/notes/07-location-sensors.md @@ -12,7 +12,6 @@ tags: - How practical are systems that are: - Precise but not accurate? - Accurate but not precise? - ![Accuracy vs. Precision](https://i.imgur.com/r0dRA8K.png) - Degrees of Freedom (DoF): @@ -24,7 +23,6 @@ tags: - 9 DoF? - Unlimited DoF? - How many degrees of freedom in 2D space? - ![Degrees of Freedom](https://i.imgur.com/uWDwFsO.png) - (Tri)angulation: @@ -33,16 +31,16 @@ tags: - Angle to reference point determined by means of special antennas - Positions of reference points have to be known - 3D-positioning requires three reference points (triangulation) - ![Angulation](https://i.imgur.com/8k8aD5h.png) +> [!INFO] if you have two reference points and the angle towards them, you can get the location - (Tri)lateration - Based on distances between device and reference points - Calculated e.g. by time of arrival (ToA) or signal strength - Positions of reference points have to be known - 3D-positioning requires three reference points (trilateration) - ![Lateration](https://i.imgur.com/KQTJDSH.png) +> [!INFO] siimilra to triangulation but you need three points and its calculated using distancees not angles. the distances can be calculated by time of arrival of a signal ## Cell-based - Positioning based on GSM cell ID @@ -53,17 +51,18 @@ tags: - Uses GSM cell ID - If sector-antennas used position can be narrowed to segment of the circle - Angulation - ![](https://i.imgur.com/uzTcwTC.png) +> [!INFO] compute your position based on which cell tower you are connected to. each tower has a unique ID. +> used by emergency providers, they know where you last logged in 2. GSM based on FDMA (Frequency-division multiple access) and TDMA (Time-division multiple access) - Exact timing required for the synchronization of uplink and downlink - Timing Advance (TA) - Device calculates distance based on signal propagation time - Can be used for positioning in combination with CGI - ![|200](https://i.imgur.com/zGMWd9E.png) ![](https://i.imgur.com/U2VHcye.png) +> [!INFO] "towers" use FDMA or TDMA [[21-data-link-layer#multiple access links and protocols]] Timing advance used for multiple access can be used to calculate time 3. Uplink-Time Difference of Arrival (UL-TOA) - Four base stations needed @@ -73,8 +72,8 @@ tags: - Network-based location technology, - Can locate any type of mobile phone. - Only available to the owner of the sensor network - ![Uplink-Time Difference of Arrival](https://i.imgur.com/CI07t5Z.png) +> [!INFO] - Integrated approach based on existing infrastructure - Low costs (for user) @@ -84,14 +83,12 @@ tags: - Information not always available to the user (often only network provider) - Used for “Enhanced 911” - But relatively low accuracy - ![](https://i.imgur.com/oLITCmM.png) - Other cell-based location approaches: WiFi/WLan-cells - Integrated infrastructure approach - WiFi/WLAN (cell-id, lateration, fingerprinting) - ![](https://i.imgur.com/VSMfEqW.png) - Based on already existing WLAN infrastructure, primarily installed for communication purposes