Let's have an overview of Basics of Remote Sensing
- Started by US military in 1973
- Three main objective: 1. Determining position, speed and time, whether in motion or at rest. 2. Contineous global 3 dimentional position irrespective to weather. 3. Useful for civilian needs
- Space Segment
- Control Segment
- User Segment
- It uses Codes (binary, zeros and ones, language of computers)
- To travel longer distances we use high energy carrier waves (L band of electromagnetic spetrum (microave region))
- C/A (Coarse Acquisition) code
- P-code (Precise - Military)
- Navigation Message/code
- [NAVSTAR GPS] (https://en.wikipedia.org/wiki/Global_Positioning_System): USA, military, fully working, will be modernized NAVigation System with Time And Ranging with 28 functioning satellites.
- GLONAS: Russia, military, fully working, will be modernized GLObal NAvigation Satellite System with 24 functioning satellites.
- [GALILEO] (https://en.wikipedia.org/wiki/Galileo_(satellite_navigation)): Europe, civil, being built up, Expected to be completely operational by the end of 2020 with 30 satellites (24 operrational and 6 active spares).
- There are also other Regional positioning systems developed by India, China and Japan.
- The quality of the data depends on the distribution of 4 satellites.
- Multipath errors
GNSS = GPS + other positioning systems (GALILEO, GLONAS, GAGAN, etc.,)
- Differential Global Positioning System (DGPS) is an enhancement to Global Positioning System that provides improved location accuracy
- Accuracy Improvement: from 15-meter nominal GPS accuracy to about 10 cm in case of the best implementations.
- By applying differential correction to code, positions can be obtained to an accuracy of 0.5 m. -Accuracy: depends upon distance between base and rover stations
- GPS Aided Geo Augmented Navigation-GAGAN
- GSAT-8 & GSAT-10; GSAT-15 scheduled for launch this year
- GAGAN is the first SBAS system in the world to serve the equatorial region
- India has become the third country in the world to have such precision approach capabilities.
- IRNSS, the Indian Regional Navigation Satellite System
- The system is designed with a constellation of 7 spacecraft and a vast network of ground systems operating.
- The first three satellites (IRNSS-1A, 1B &1C) were launched in 2013-14.
- IRNSS-1D, the fourth satellite of IRNSS constellation was successfully launched on March 28, 2015 on board PSLV-C27
- The unique Geostationary Earth Orbit (GEO) /Geo Synchronous Orbit (GSO) constellation design provides a position accuracy of better than 15 metre for longer duration of 20 hours in a day even with 4 satellites
- http://www.aces.edu/pubs/docs/A/ANR-1352/ANR-1352.pdf
- http://geology.isu.edu/geostac/Field_Exercise/GPS/GPS_basics_u_blox_en.pdf
- https://books.google.co.in/books?hl=en&lr=&id=bQntCAAAQBAJ&oi=fnd&pg=PR19&dq=Global+Positioning+System&ots=tsc8nwQdJN&sig=lHpul3Zg6b2a7BbE4b-7GJ_KwvA#v=onepage&q=Global%20Positioning%20System&f=false
- https://sites.google.com/site/artificialsatellitestelescopes/artificial-satellites/the-orbit