الاستشعار عن بعد: أنواعه، وتقنياته، وأجهزته ....Remote Sensing: types, techniques, and its organs

Remote Sensing: types, techniques, and its organs

First: the definition of remote sensing

There are many definitions of remote sensing, with the following presentation of the four most important of these definitions:

1. Means of remote sensing total number of operations, which allow to obtain information about something, without there being direct contact between him and the capture device this information.

2. Remote sensing is the science, which uses the properties of electromagnetic waves reflected or emitted from things terrestrial, or from the air, or sea water has been identified.

3. Can be considered remote sensing that: the set of means, from aircraft or satellites, or balloons, and data capture devices, and receiving stations, and a data receiving-processing programs, which allow the understanding of materials and phenomena through the spectral properties.

4. Remote Sensing: the science can be obtained on the reflection data and spectral behavior of things, which can be transformed into information through the processing and extrapolation.

So the expression "remote sensing" is used to mean data set, we get from a certain distance; the result of the interaction energy of electromagnetic radiation with matter, or appearance which we teach, and the measured one of the means of remote sensing instruments.

These tariffs - albeit inclusive - it is a high degree of complexity, sometimes, what is included in the study of land and wealth, which is not far away from the devices, making use of the word "after" subject to question at times. Some believe that the other media that are contrary to energy radiation, real-time audio, for example, must be covered by this tariff.

Secondly: the types of remote sensing

Can be classified as remote sensing, according to the type of data receiving to:

1. Remote sensing positive Active Remote Sensing: The data receiving the spectral reflections, where the platform carrying the sensor sends electromagnetic waves to the targets to be studied, Fterttm, and reflected to be picked up sensors Sensors, that you send to ground receiving stations Ground Reception Stations.

2. Remote sensing negative Passive Remote Sensing: The data are receiving the emission spectroscopy of objects, (see the form of taking spectral emission).

Third: remote sensing techniques

Based remote sensing techniques to carry multiple types of sensors Sensors, to record the phenomena to be studied and measured, based on the concept; that every object radiates and reflects the range of electromagnetic energy, often in distinct groups, called "spectral signatures" Spectral Signature, describes information about specific property of the body.

In general, it is possible to transmit radiation through the body, or absorbed by the body, or by distracting the body, or may be reflected radiation, which means that the return of radiation without change, which is the body in this case is like a mirror.

And determine the selection of one of these interactions the former wavelength for each substance, which depend mainly on the properties of its surface and molecules, and these are the rules of measurement by remote sensing. It should be noted that the Earth's atmosphere some features of its own, and influential bands in the selection of the optical sensor.

The accuracy of each device is different from the other A_i_ari degree of differentiation [1] Resolution, it achieves in the monitoring of goals, depending on the properties for each article to reflect the light beam it, or the absorption of these rays, in part or in full.

IV: The mechanism of remote sensing

Is a mechanism of remote sensing through four stages:

1. Collection of information by sensors, and left to ground receiving stations.

2. This information is subject to initial treatment and corrections, and then address the final.

3. The interpretation of these data converted to images.

4. Use of images in the design of accurate data and maps, which serve different areas.

Fifth: remote sensing instruments

Remote sensing devices, mechanical or electronic, they can be regular camera most common forms of remote sensing instruments, such as the eyes as it completely, use light reflected from the body, passing through different lenses, the light-sensitive surface to form a picture, and is also used machine photography to record events, we want to remember, we can use this camera to get the appropriate information, to a particular subject, we are studying.

Although some of the remote sensing instruments capable of giving information / data continues to run the same time, the most remote sensing instruments are storing data, in one way or another. Also, the amount of data usable in the image is greater than in the constantly changing images, and video on a display device is.

Digestive remote sensing devices, therefore, is that data collected, is usually subject to storage of objects or scenes from a certain distance of them, and some of these devices, photo agencies, energy use visible light [2], while others use other types of energy, There are sensors on the less common of the cameras, as organs radar and X-ray X-Rays.

Fbastamal X-ray, for example, can be a distance slightly larger than the thickness of the layer of the skin or tissue, and the most important difference is the nature of the radiation used in each system. For radar, X-ray is different wavelength of radiation used is the reason which gives advantages both of the two systems for specific scientific missions.

1. Platforms carrying remote sensing instruments

The primary purpose of platforms, carrying remote sensing instruments, is to put these devices on a certain height from the ground. Used balloons and aircraft in remote airspace for aerial photographs of large scale and medium, from 2000:1 to 8000:1, according to a high balloon or aircraft, which ranges between 3000 and 7000 meters, and balloons may be addressed or not addressed, depending on the track wind.

The third type of platforms is the spacecraft, and this type of platforms is expensive, and requires high-technology level. These compounds were of two types: moving in paths Orbits around the globe, fixed Geostationary, which characterized her with a permanent, fixed position in relation to the Earth, thus providing a permanent and continuous observation of the portion of the globe.

2. Mobile data capture

Data capture devices that receive the radiation emitted and reflected, for certain wavelengths, then converts it to radiation, are sent to ground receiving stations. Divided capture devices of remote sensing data to the following main types:

A. Imaging devices (see the form of a method of photography)

B. Radar, remote capture device is positive, where it is broadcast ray, captured, and sent to ground receiving stations.

C. Usually provide satellite Ptlscobat huge increase the accuracy of the capture radiation. The French satellite "SPOT" SPOT with two of these telescopes, which each weighing 250 kg, with a length of two and a half meter, and after taking pictures by the visual system, drop the light on the optical sensors, which are each composed of 1000 pixels, turning lights into electrical signals.

3. Devices used in the study of oceans and seas

And some sensors carried by satellites negative, such as measuring radiation "Alradiomitr" Radiometer, and detected by the emission of natural radiation from the sea, or as reflected in the sea of sunlight.

There are other sensors are positive, send radar waves through a hole radar synthetic Synthetic Aperature Radar: SAR, Vttold agree tarnished image the amount of energy reflected from the surface of the sea in the form of a microwave. Controls the generation of photo sea level conditions, and the extent of disturbance, and the movement in general. Images, obtained by the radar, can reveal details of some properties, such as movements typical of the Interior, or the topography of the bottom, to a depth of several meters.

A. A device to measure the rise

And the altimeter Radar Altimeter doing the action may be particularly important to measure the sea level, and then the degree of decline within a few centimeters of accuracy. This means that, thanks to altimetry can reveal the diversity of ocean currents, on a gross basis, and can measure the size of swirls around, vast areas of unrest, such as the swirling seas of the South.

And recording the time of broadcast of radar wave in its journey from the satellite to the sea and the time received, and study the form of this wave when she comes back give evidence of the turmoil the sea. Therefore, this device provides a means to monitor the high waves at all times, which is an important variable in navigation.

B. Scatterometer

The scatterometer Disperometer radar covers an area more broadly. Valhdp medium-wave radar, is a measure of the disorder as a result of the sea wind. Thus, this detection method, provide a means for measuring the wind on the sea surface in large areas, not only crossed regular ships, or ships of Meteorology. And weather forecasts can be improved by incorporating such information to weather forecast models.

Despite the problems, caused by clouds, which covers the air, the sensors, which measure the infrared radiation emitted from the sea, given the images of sea surface temperature. Oceanographers and uses this information to monitor the violent eddies in the ocean, or the border between water masses, which have different temperatures.

In shallow seas, according to the temperature in the detection of water flows from foreign estuaries, or discrimination water masses, which does not seem to dissipate in the open sea and, therefore, could be indicative of the presence of swarms of fish.

There are many methods, which use remote sensing in the seas and oceans; including:

(1) aerial photography: It is used to study the pollution of seas and oceans, and location of waste-oil spills from ships passing incumbent seas and oceans, beaches and the demarcation of the seas and oceans, and determine its forms.

(2) imaging in the areas of multi-optical: used to locate plants and distribution, and mapping of water depths, the study of currents and thermal movement of water associated with them, and to identify sites of industrial wastes, and spread along the beaches, and study the distribution of water and suspended sediments in lakes, and study the distribution of chlorophyll and areas of focus.

(3) of the thermal survey: is used to identify the current systems and thermal spread in the water, In a study of water quality and natural characteristics, the location of patches of oil floating on the surface of the water.

(4) scanning radar: used to measure the surface properties of sea water and the ocean, and study the conditions of sea waves, the location of oil spills and areas of sour water, suspended matter near the surface, and study some physical properties of water and its quality.

Carrying satellites for the study of sea and ocean scientific instruments for measuring, monitoring and photographing the following elements:

(1) wind speed.

(3) contouring the surface of the ocean.

(3) measure the temperature of the surface.

(4) measurement of surface wave and deep ocean.

(5) determine the main currents in the ocean.

(6) monitoring of ocean eddies.

(7) monitor and measure the movement of ice.

(8) monitoring and follow-up oil spills.

(9) Monitoring and follow-up fish and marine life.

4. Mobile data analysis and processing

Bodies of the analysis and processing of data from:

A. Computer memory ever, so much so being able to store more pictures and study it. When digital data processing of images of space, you can use any of the levels of computer systems the following:

(1) Personal Computer Personal Computer

(2) Workstation Work Station

(3) the main network Main Frame

These levels differ mainly in the number of instructions or orders, which are processed per second, allowing both the workstation and the primary network number of the screens and keyboard, allowing more than one person working at the same time.

B. Copier large Plotter, and are used for the printing of maps resulting from the division of digital data, known as multi-spectral emission maps, set computer (see the picture of the spectral emission).

C. Copier small, and are designed for the printing of numbers, statistics or any place on the digital data, as well as used for the printing of maps on paper.

D. A study and analysis of digital data, which holds the discs, which operates independently of the computer.

5. Assistive devices to understand the spectral behavior

These devices help to understand the spectral behavior of materials and objects, and these devices include the following:

A. Device to measure the impacts or emissions, and know Balradiomtr Radiometer. Alradiomtr devices and the way they put it on the ground are two types, one set on the ground by means of a single-feet, or three feet, at an altitude of about 1.5 meters above the ground, and the other type of these devices can be carried by hand.

In both types are captured reflection data from the floor area ranging from 1 to 1.5 square meters, according to how high the measurement. On any radiometric measurements should be taken into account the date of the study, an hour or time data capture, and climatic conditions, as well as taking angle reflection data or captured, and the need for calibration Calibration of the device before using it.

B. Scanner-dimensional infrared ray Spectrometer Sbactromitr The basic idea in this device is the presence of a light source light beams issued on the sample to be measured implications.

C. My Isbactromitr Infrared Infrared Intelligent Spectrometer (IRIS): This device works on the emission spectral curve through the spectral range from 300 to 3000 nm [3], as well as recording digital data for this curve continuously, and can be used in field studies and laboratory together, Thus, it combines the properties of a Alradiomtr, in terms of field-use, and characteristics of a Alisbactromitr in terms of continuous measurement of emissions over the total spectral range.

6. Mobile GPS Positioning

These devices are used to determine the coordinates for the areas of screening and the field study, which identified based on the study and manage their photos. These devices include a location Konya Global Positioning System: GPS, which connects with about 12 satellites, including the determination of the coordinates. And verify the correct reading of the availability of communication between the device and the four satellites, at least, and vary depending on the accuracy of the device type.

It is worth mentioning that when dealing with remote sensing; the zero line of the longitudinal coordinates of the line is GMT, or the zero line of the coordinates of the spin-off is the equator, the distance measurement unit is the meter.

VI: remote sensing using microwave

The idea that remote sensing using microwave Microwaves, or the so-called "Remote Radar" to the transmission of electromagnetic waves in certain ranges (see the table of the frequency band radar), the target to be studied, and then receive the waves reflected from it.

As a result, the role of radar in the transmission of this wave and its non-self-electromagnetic emissions from the body, as is the case in remote negative, this type is defined as "remote positive".

The radar is picking up profiles, or sectoral. The equipment is in force synthetic "went" Synthetic Aperture Radar: SAR, (see the picture of the radar antenna SAR), it sends impulses to the target area, has been reflected energy. Rough surface reflects radiant energy over soft surfaces, Vstouh the mountains, and the flow of molten rock, for example, appear bright sources in the radar images.

By measuring the time it takes signals to travel the distance from the radar to the target and return, can be measured by the relative heights of different terrain. And recorded radar signals reflected on the holographic film in a manner [4] Holographic, are then converted using a laser beam to images give a sense of Baltjsim, ie, three-dimensional imaging, (see picture three-dimensional model of a ship.)

1. Radar moon "of policies"

The first civilian imaging radar was placed in orbit around the Earth, was on board the satellite ocean-called "policies for" Seasat, launched in 1978. Although he has served for less than four months because of an injury bug, he stressed the survey, conducted by that of the ocean surface lines are quite specific, such as land, and there are areas above the other regions, including more than 250 meters.

These rises and falls as a result of differences in gravity resulting from the uneven distribution of mass within the Earth. Upon receipt of this information from the Moon "of policies", drawing scientists Jet Propulsion Laboratory, Institute of Technology in the "Bacdin" California, the image of the seabed in the world, is expected to be used as a guide to future discoveries, and give rise to new thinking about the geology of the planet.

2. The radar system of the shuttle "Columbia"

Space shuttle "Columbia" was carried in his second trip in November 1981, radar system designed to clear the land. Have been installed over the resulting image pictures "Landsat"; to highlight the integrated nature of the techniques, by mixing high-resolution radar images of Earth, and multi-spectral vision of the chemistry of surfaces, provided by the "Landsat", as is the case in the types of rocks and vegetation. The resulting composite image appeared, which gives the colors are not true, amazing as it contains the information.

But more discoveries, which resulted from the analysis, is the Space Radar Views, under the sands of deserts. In areas of micro-drought, show that the radar signals penetrated two meters to three meters of sand, and in some cases, about five meters, and often hit the rocky base.

When the moon across the sky Sudan and southern Egypt, pick up the radar images, revealed the effects of buried rivers; once flowed there, and dug for itself valleys, the view the view the Nile now.

Geologists and was followed by drilling holes in the desert, and confirmed the existence of a network of drainage basins old, and found sites of buried human settlements when the Sahara was less arid. And reporting on these findings the experts concluded that the potential presence of groundwater near the surface, enough to generate interest among scientists, who now have a way to explore the deserts on the planet.

3. Satellite radar, "Radar-1"

Satellite radar, "U.S. radar -1" Radar-1, is the first satellite, called for military use and civil at the same time. The radar will provide images, have a degree of clarity, resolution up to one meter.

This is based on satellite radar technology with a window of synthetic "went" Synthetic Aperture Radar (SAR), which allows to take pictures during the day or night, in any weather conditions, unlike the visual images in the traditional satellite imaging, (see the picture of good air radar ).

And return the consent of the American military circles, to grant the license, has launched a civilian satellite, radar, the desire to provide funds budget of the Ministry of Defense, with the aim to take advantage of the technological developments achieved in the private sector. However, satellite radar "radar - 1" subject to state control, as it should be invested on the company to obtain special permission from the U.S. government before selling any photo radar, at a resolution of up to five meters or less, to a client civilians.

The main advantages of using radar remote sensing are:

A. The flexibility of radar data

Designed devices used in radar remote sensing purposes so that you can control the inclination of the radar beam on the vertical axis at ground level, so this angle ranged between zero and 60 degrees. This has led to the possibility of daily monitoring of natural phenomena, and I knew this feature multi-time coverage, or follow-up of the phenomenon that, in times of high activity changes, through studies detect changes.

The area covered by the radar scene, ranging from 50 × 50 km, in the case of micro-beam, and 500 × 500 km, when you use the radar beam of the radar window ever synthetic Synthetic Aperture Radar: (SAR). And the degree of differentiation ranged between 8 m and 100 m.


And of course, helped to expand the application fields of radar data and multiplicity of the discovery of oil, gas and minerals, and environmental impact assessment, and show the natural disasters and follow-up, and show the crop and follow-up, and the work of ground mapping and coastal management, and demonstrate the uses of land and follow-up.

B. The ability of radar to penetrate clouds

radar sensor is characterized by the ability to penetrate clouds, fog, rain, dust, and darkness. This leads to capture continuous images of the radar during the day and night, both in, and the importance of this ability Penetrometer in the tropics, coastal and Arctic. This is not available for Satellite Remote Sensing negative.

C. Continued access to radar data, and follow-up semi-real-time dynamic of the phenomena

and the frequent passage of the satellite carrier for the radar, above the site of the globe, serve to obtain several images every day; allowing follow-up, almost instantaneous. Under normal circumstances, vary the period between visits depending on the type of radar the radar beam, and therefore vary the degree of differentiation, as well.

and stop between repeated visits to the subject itself, in addition to the type of the radar beam on the lines of latitude and longitude for this site, where this period is increased in the direction of the equator, and less time at other latitudes of the short distance between them, and thus increase the number of tracks that can be repeated daily.

D. The possibility of seeing the same site from two different

radar provides the potential to see the same site from different directions, thus getting the pictures of an area, from two opposite sides, which helps to get as much information as possible.

E. The ability of the fusion of radar data with other data

This ability show greater geo-information, when the integration of radar data of geophysical measurements [5] Geophysical Measurements information is available on the surface of the earth, and under the earth's surface.

And. Multi-degree of differentiation

The multitude of the degree of differentiation of the radar data, and different from 8 meters to 100 meters, the multi-scale mapping resulting commensurate with the purpose of the study. For example, data can be used radar beam minute or standard of the work of the detailed maps, while the use of the radar beam data (SAR) for the preparation of maps at the district level
Regional Mapping.