HYDRO (LEC 3)

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designed to measure the time of transit or difference in transit times of electromagnetic waves in the atmosphere.

Electronic Positioning System

EPS requires a relay unit on shore which must be equipped with a ____, ______ and an _____.

transmitter, receiver, amplifier

EPS is a typical system consists essentially of transmitting on a ______ ______, an ______ ______from the ship to the three triangulation stations of known position

fixed frequency, unmodulated radio waves

The accuracy of any measurement by an electronic positioning system is highly dependent upon the ______, _______, and ______ at the time the measurement is made

temperature, humidity, pressure

Classification of Electric Positioning System

Short Range, Intermediate Range, Long Range

originally developed for blind bombing by military aircraft and aerial photographic reconnaissance.

SHORAN

widely used now often in most offshore measurements and in establishing triangulation stations for horizontal control networks.

SHORAN

SHORAN was often used for ___ ___ in military

blind bombing

SHORAN was usually employed when ____________________ is required even under adverse weather conditions.

rapid determination of position

SHORAN operates on ___ frequency

low

range of SHORAN

80-120 km

With Shoran, distances can be determined to __ or even __ of a kilometer

hundreds, thousands

principle employed is similar to Shoran

LORAN

Principle employed is similar to Shoran except the use and transmission of _____

high pulse of electromagnetic energy

Loran follows the ____ better than low-frequency waves

curvature of the Earth

What does EPI means?

Electronic Positioning Indicator

combines some of the principles and techniques used in long-range and short-range navigation.

Electronic Positioning Indicator

Who developed the Electronic Positioning Indicator?

US Coast and Geodetic Surveys

Distance of Electronic Positioning Indicator

500-800 km

used to determine the position of survey vessel

Radio Acoustic Ranging

What does RAR stands for?

Radio Acoustic Ranging

Advantage of RAR

Independence of the conditions of visibility

Method of measuring the depth of water

Echo Sounding

Instrument used for determining the depth of water by echo-sounding by which has an indicator scale which is graduated to read depths directly instead of time

Fathometer

Instrument used for determining the depth of water by echo-sounding by which has an indicator scale which is graduated to read ____ directly instead of time

depths

Fathometer display the depth visually in _______ form and others produce an _________ or _______ in a roll of specially prepared paper.

digital, analog graph, strip chart

Fathometer is designed to

produce the sound, transmit the sound downward, receive and amplify the echo, measure the intervening time interval, automatically convert the interval into units of depth measurement

Types of Echo Sounders

Portable Fathometer, Non Portable Fathometer

mounted on a small boat or suspended over the side.

Portable Fathometer

Portable Fathometers are operated by _______ and can be easily shifted from one boat to another

dry batteries

up to how many depths can be read in a portable fathometer

60 m

considered part of the navigation equipment of the or survey sounding vessel

Non Portable Fathometer

Non portable fathomeresigned to measure sounding to depths of _______ to an accuracy of about ________.

over 60 m, 1/2 cm

Graphic recording and draw continuous profiles of the sea-bed on a moving strip of paper

Non Portable Fathometers

For echo sounding, the medium is the ____ and the reflecting surface is the _______

water, sea bed

recently copied by echo sounders to provide an intermediate printout of sounding depths and their related positions.

Electronic Digital Computers and Plotters

developed to allow interpolation between plotted depths and plotters are utilized to draw the depth (bathymetric) contours automatically just as in automated plotting for topographic surveys

Computer Programs

employs lasers, offers high accuracies but is applicable only to depths less than 50m.

LIDAR

Soon expected to replace conventional hydrographic survey methods performed on board sounding vessels.

Multi Spectral Scanners

a pulse-type laser is used to emit a burst of light which is reflected at the water surface and at the bottom of the body of water.

Airborne Lasers

Systems are based on the principle that less energy is returned from deep waters than from shallow waters, calibration of such a system is done by comparing returned energy with known water depths.

Orbiting Satellites

Allow remote measurements of water depths.

Orbiting Satellites

an aerial camera is used to photograph the water areas using standard techniques of photogrammetry.

Photobathymetry

New Developments in Electronic Sounding Equipments

Electronic Digital Computers and Plotters, Computer Programs, Light Detection and Ranging, Multi Spectral Scanners, Airborne Lasers, Orbiting Satellites, Photobathymetry

First Landsat Satellite was launched by _______ and when?

United States of America, July 23, 1972

the spacecraft was equipped with a multispectral scanner which had the capability to view a 185-km wide strip of the Earth’s surface on an 18-day repetitive cycle.

ERTS

First Landsat Satellites Altitude: Weight: Interval of Circling the Earth: Wide Strip:

919 km, 891 kg, 1 hr and 43 mins, 185 km

In ____ , it was decided to rename ERTS to ____

1974, Landsat

Landsat emits four bands of the spectrum

red, green and 2 infrared

unit used in remote sensing to express the wavelength of an electromagnetic spectrum.

Nanometer

water is quite transparent in this band and it tends to enhance features such as sediment with water.

Green Band

Wavelength range of green band

500-600 nm

Penetrates the atmosphere and is suitable for landuse studies.

Red Band

Wavelength range of red band

600-700 nm

M#5 Section and Title v2

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M#5 Section and Title v2