Slide 1: Introduction to Remote Sensing Physics project on SONAR What is SONAR? : What is SONAR? So - Sonographic
Na - Navigation
R - Ranging It is a method for detecting and finding the distance of objects underwater by means of reflected ultrasonic ways. The device used in this method is also called sonar Slide 3: Actually animals use echolocation and that is actually where we learned the technique
Bats, whales, and dolphins are some of the best known animals to use echolocation Who else uses sonar ? What does the Sonar consists ? : What does the Sonar consists ? (1) a hydrophone
(2) an electronic receiver
(3) a bearing indicator
(4) a speaker or headphone Slide 5: Working of sonar Sound Properties : Sound Properties Sound travels 1460 meters per second (approx. 1500 mps), in water, not in a vacuum
Sound waves are measured in hertz (Hz). The human ear can detect frequencies ranging from 20 Hz to 20,000 Hz. Navigation and Ranging Issues : Navigation and Ranging Issues Depth is determined by dividing travel time of sound by 2 and then multiplying by 1500 mps
If 12 seconds was the travel time, then
12/2 = 6X1500 = 9000 meters deep
Frequency of sound appears to increase when an observer moves toward a source and appears to decrease when he moves away from it. Similarly, if the source is moving toward the observer, the frequency is higher; if the source is moving away from the observer, it is lower. What do we use sonar for ? : What do we use sonar for ? First developed in WWII to detect submarines
Used to detect icebergs
Calculating Water depth
Locate sunken ships/or other historical objects
Military uses it still to detect subs and aim weapons
Locate fish or track animals that are being studied
Mapping underwater features How a map is made with a imaging sonar ? : How a map is made with a imaging sonar ? A Sonar echo recorder is dragged behind a ship and is called a towfish
It sends out a ping … sound travels to the bottom and is reflected back to the hydrophone
An instrument on the ship collects and analyzes the data
These points of data are combined to create a picture of the seafloor Side-Scan Sonar Systems : Side-Scan Sonar Systems The sound frequencies used in side-scan sonar usually range from 100 to 500 kHz
Designed to look sideways and at a downward angle from both sides of a towed unit, called a towfish. The bottom and any objects in the water above the bottom reflect sound waves back to the towed array. An image is produced from this information . Types of Imaging Sonar Single-beam Sonar Systems : Single-beam Sonar Systems The ship sends out a single beam of sonar to the sea floor, kind of like a flashlight beam.
Used primarily for mapping channels and bathymetry for hydrologic and engineering applications. Multi-beam Sonar Systems : Multi-beam Sonar Systems Multibeam sonar sends out many beams of sound waves to the sea floor. The equipment is usually mounted on the bottom of the boat.
Scientists use the time measurements to figure out how deep the water is.
Because of its ability to produce highly accurate depth measurements over a wide area, Multibeam sonar is most often used for bathymetric surveying. WE SHALL NOW BE PRESENTING A VIDEO ON WORKING OF SONAR... : WE SHALL NOW BE PRESENTING A VIDEO ON WORKING OF SONAR... Slide 17: A Project Guided By Megha Ma’am A project by :- Narendra Bhusakhare (9541) Kamran Ahmed (9550) Rishi Raj Tripathi (9552) Gaurav Sharma (9551) Slide 18: THANK YOU……