Sensors and navigation Flashcards
List 4 basic forms of navigation
1) celestial navigation
2) dead reckoning
3) radio navigation
4) inertial navigation
Describe celestial navigation
using time and angles between local vertical and known celestial objects to estimate the orientation, latitude and longitude of the moving object
Describe dead reckoning
relies on localising landmarks to know where you are and how you are oriented
Describe radio navigation
relies on radio frequency sources with known locations (GPS, reference nodes)
Describe inertial navigation
relies on knowing your initial position, velocity and attitude.
Only navigation that does not rely on external references
Define a sensor
a device which receives a signal or stimulus and generates measurements that are functions of that stimulus
usually consists of a transducer (converts a physical or chemical quantity into an electrical signal)
List and explain 2 main sensor groups
1) Passive sensors
- directly generate an electric signal in response of an external stimulus. Do not require an additional power source (e.g. infrared sensor)
2) Active sensors
- require external power for their operation which is called an excitation signal (e.g. radar)
Explain how RADAR works
- RAdio Detection And Ranging Uses speed = distance/time speed - speed of EM wave time - measured distance - calculated
Describe difference between primary vs secondary RADAR
1) Primary
- operates independently of the target aircraft
- lots of power required
- sends a signal and tries to pick up return
2) Secondary
- relies on a ‘transponder’; a unique 4-digit code transmitted
- ground receives and responds in coded messages
List 7 applications for RADAR
1) Air Traffic Control
2) Ballistic Missile Defence Over-the-horizon RADAR
3) Air Defence Search and Tracl
4) Satellite Remote Sensing - geography, environmental systems
5) Ground Penetrating Radar - rail track and buried pipe fault detection
6) Missile control and seeker guidance
7) Ground surveillance and reconnaissance using imaging radar
- all work on same principle but different frequency bands
Define azimuth
the angle between north and a line pointed directly at the target. measured clockwise and in the horizontal plane from true north
Define elevation angle
the angle between the horizontal plane and the line of sight, measured in the vertical plane
+ve above the horizon
List basic components of a LIDAR system
- a laser scanner
- cooling system
- GPS
- Inertial Navigation System
List 3 segments of GPS
1) Basic functions of the satellites
- transmit info
- receive data
- maintain accurate time
2) Control segment
- ground facilities
3) user segment
What is GLONASS
Global Orbiting Navigation Satellite System - Russian GPS
24 satellites (21 used, 3 spare)
dual-frequency
