From 1030f967ae1bef538251527375134bc3a00646de Mon Sep 17 00:00:00 2001 From: Jet Hughes Date: Thu, 23 Mar 2023 10:39:03 +1300 Subject: [PATCH] vault backup: 2023-03-23 10:39:03 --- content/notes/08-proximity sensors.md | 53 +++++++++++++++++---------- 1 file changed, 33 insertions(+), 20 deletions(-) diff --git a/content/notes/08-proximity sensors.md b/content/notes/08-proximity sensors.md index 14fb14cca..40d8dc930 100644 --- a/content/notes/08-proximity sensors.md +++ b/content/notes/08-proximity sensors.md @@ -85,16 +85,22 @@ Proximity Sensors & Near Field Communication 11 - Data exchange rate today up to 424 kilobits/s - Usually used for Smartcards, digital payment, or device to device communication/ authentification NFC smartcards -Proximity Sensors & Near Field Communication 12 NFC-based communication / authentification +> [!INFO] small transmitters can be read with a large reader +> nfc is one specific spectrum of rfid + +![Proximity Sensors & Near Field Communication 12 NFC-based communication / authentification ](https://i.imgur.com/WwidfDA.png) +> [!INFO] phones are a reader. but they can also emulate a tag Proximity Sensors & Near Field Communication 13 - Each full NFC device can work in three modes: - NFC card emulation -- NFC-enabled devices act like smart cards, allowing users to perform transactions such as payment or ticketing. + - NFC-enabled devices act like smart cards, allowing users to perform transactions such as payment or ticketing. - NFC reader/writer -- NFC-enabled devices to read information stored on inexpensive NFC tags embedded in labels or smart posters. + - NFC-enabled devices to read information stored on inexpensive NFC tags embedded in labels or smart posters. - NFC peer-to-peer -- Enables two NFC-enabled devices to communicate with each other to exchange information in an adhoc fashion. 14 + - Enables two NFC-enabled devices to communicate with each other to exchange information in an adhoc fashion. 14 + +> [!INFO] Three modes. emulation, writer, p2p. Proximity Sensors & Near Field Communication - Different technologies for sensing proximity or exchanging data (often dual purpose) @@ -104,27 +110,30 @@ Proximity Sensors & Near Field Communication GPS - Overview - (Navstar-) GPS is a satellite-based navigation system that provides users with Positioning (and Timing services -- Provides information anywhere on Earth with unobstructed Line Of Sight -- Operates in any weather conditions (but with accuracy constraints) -- Available to military, commercial and civil users + - Provides information anywhere on Earth with unobstructed Line Of Sight + - Operates in any weather conditions (but with accuracy constraints) + - Available to military, commercial and civil users - Similar systems: -- Glonass (Russia, Operational) -- Beidou/Compass/Beidu 2 (China, operational since 2020) -- Galileo (Europe, expected operational since 2020) -- Local coverage (DORIS, IRNSS, ..) + - Glonass (Russia, Operational) + - Beidou/Compass/Beidu 2 (China, operational since 2020) + - Galileo (Europe, expected operational since 2020) + - Local coverage (DORIS, IRNSS, ..) + +> [!INFO] initally only for millitary. now open to anyone but need under open sky GPS - Applications - Numerous GPS applications & GPS Receivers: -- Military -- Car navigation -- Marine -- Flight control -- Agriculture -- Recreation + - Military + - initally for remote guided bombs + - Car navigation + - Marine + - Flight control + - Agriculture + - Recreation - For mobile devices -- Car an personal navigation -- Location-based services -- Augmented Reality + - Car an personal navigation + - Location-based services + - Augmented Reality GPS - History - GPS project was developed in 1973 by U.S. Department of Defence (successor of Transit/NAVSAT @@ -135,6 +144,10 @@ GPS - History - Accuracy errors of 100m - SA was removed for civilian users in 2003. - GPS achieved initial operational capability (24 Satellites) in 1993 GPS – Satellites + +![original gps diagram](https://i.imgur.com/PJYIoMo.png) + +GPS – Satellites - Constellation of 24 + X satellites transmitting radio signals to users - Altitude of 20,000km (approx.) - Each satellite orbits Earth twice/day