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Fundamentals of Remote Sensing
Long different methods for gathering data, particularly data spatial exists. Astronomical observation, land surveying, hydrographic, photogrammetry and remote sensing methods for major data collection is spatial. Remote Sensing (Remote Sensing) from among the methods of data collection is considered in which physical contact with objects measured in at least may be kept. Methods of land against which the human factor in their duty to interpret and is responsible for harvesting, usually in direct contact or from objects with low distance is done in remote sensing, data gathering sensor is responsible.
Since definitions for many remote sensing has been presented that some of the most important ones are:
- Remote sensing image interpretation and processing of knowledge is the result of record energy electromagnetic interactions and objects are (Sabins, 1997).
- Remote sensing means harvesting surface properties from space using electromagnetic waves reflected from the surface of objects, or is released. Application of remote sensing in natural resource management, production of maps and user coverage and preserve nature (UN, 1999).
- Art and science of remote sensing to obtain information about an object, area or phenomenon through the processing and analysis of data obtained by a device (without direct contact with the object, or phenomenon, the study area) is. (ASP, 1983)
Although this definition is a little old, but greatly important functions and capabilities of remote sensing has expressed. Based on this definition and ongoing remote sensing can be a remote sensing system to be divided into two parts:
1 - data collection
2 - Department of Information Extraction
Part of data collection, data measuring the distance from which the form of images, photographs, data, height and so users are presented.
This section consists of four basic elements:
1 - Origin Energy (Energy Source), electromagnetic waves and producing it through the atmosphere toward the objects are sent there. Often the source of solar energy, but in some systems measure energy source away from the sensor is the electromagnetic waves at certain wavelengths is generated.
2 - Atmosphere: source of energy wave that travels toward objects in their path through the atmosphere called passes important effects on energy atmosphere posts include: absorption and scattering


3 - Objects and phenomena: a part of the electromagnetic wave interacting with the atmosphere will finally approach to the objects and part of it reflected, part absorbed and part of the object passes. Part reflected back through the atmosphere and outer space leads to the sensor part of it is reached.
4 - Sensor: The sensor of energy sent from the objects received, can measure and record. Sensor for maintenance and transfer (in orbit or in space) are needed platform aircraft or satellite is often.
Interaction of the four mentioned components is usually a picture that can be used to extract information. In next phase files can be analyzed to extract the needed information. As a whole, analysis of images, theoretically, can be mapped with data that is done in both methods of visual interpretation (traditionally methods) and computer methods. In the first method, expert with the help of creation of different colorful combinations and past experiences is identified features based on color, texture and other parameters but in the computer technique, in spite of the human factor, the final decision is involved in with a computer algorithm that each pixel of the image belongs to a class or a feature on earth.
This brief introduction to remote sensing, although are not with many details, but it can create a general view about type of the process and operation of a remote sensing system and or where plays the role each part of the process.


keywords
remote sensing    energy source    photogrammetry    electromagnetic    sensor