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Remote Sensing

Remote sensing is the art, science, and technology of obtaining reliable information about physical objects and the environment, through the process of recording, measuring and interpreting imagery and digital representations of energy patterns derived from non-contact sensor systems (Colwell, 1997)

Colwell, R.N., 1997. History and place of photographic interpretation, Manual of Photographic

interpretation, W.R. Philipson (Ed.) 2nd Ed., Bethesda: American Society for Photogrammetry & Remote

Sensing, 33-48.

A remote sensing instrument collects information about an object or phenomenon within the instantaneous-field-of-view (IFOV) of the sensor system without being in direct physical contact with it.

The sensor is located on a suborbital or satellite platform.

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Remote Sensing Platforms and Sensors

Electromagnetic Radiation (EMR)

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Spectral Response: EMR patterns are recorded by sensors.

http://www.cas.sc.edu/geog/rslab/Rscc/mod1/emrpaths.gif

Spectral Response

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Remote Measurement

Robert Green at NASA's JPL suggested to use "remote measurement" because data obtained using new technologies are so accurate (Robbins, 1999).

Robbins, J., 1999. High-Tech Camera Sees What Eye Cannot," New York Times, Science Section, September 14, D5.

What is remote sensing?

An image of the D.C. area by GeoEye-1 (“Google satellite”) :Lunched 09/06/2008, the satellite is 423 miles above the Earth. While it moves 17,000 miles per hour, it will still be able to look down at the Earth and see objects about a half meter in size.

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What is remote sensing?

This GeoEye Satellite Image taken at 11:19AM EDT shows Washington D.C.'s National Mall and the U.S. Capitol on Jan. 20, 2009 during the inauguration of President Barack Obama. Photo: AP

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Remote sensing observation and in situ measurement

Remote Sensing vs. in situ Data Collection

In remote sensing sensor systems record energy levels, by electromagnetic radiation (EMR) , directly and indirectly reflected or emitted from the ground targets.Most of the in situ data collection involves going out in fields and questioning the phenomena of interests.

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Remote sensingRemote sensing is a tool or technique similar to is a tool or technique similar to mathematics. mathematics.

Using sensors to measure the amount of electromagnetic Using sensors to measure the amount of electromagnetic radiation (EMR) exiting an object or geographic area radiation (EMR) exiting an object or geographic area from a distance and then extracting valuable information from a distance and then extracting valuable information from the data using mathematically and statistically from the data using mathematically and statistically based algorithms is a based algorithms is a scientificscientific activity. activity.

It functions in harmony with other It functions in harmony with other spatialspatial datadata--collection techniques or tools of the collection techniques or tools of the mapping sciencesmapping sciences, , including cartography and geographic information including cartography and geographic information systems (GIS) (Clarke, 2001).systems (GIS) (Clarke, 2001).

Physical Sciences

BiologicalSciences

Interaction Model Depicting the Relationships of the Interaction Model Depicting the Relationships of the Mapping Sciences as they relate to Mathematics and Mapping Sciences as they relate to Mathematics and Logic, and the Physical, Biological, and Social SciencesLogic, and the Physical, Biological, and Social Sciences

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Information about an Information about an Object or AreaObject or Area

The EMR reflected, The EMR reflected, emitted, or backemitted, or back--scattered scattered from an object or from an object or geographic area is used as geographic area is used as a a surrogatesurrogate for the actual for the actual property under property under investigation. investigation.

The electromagnetic The electromagnetic energy measurements must energy measurements must be calibrated and turned be calibrated and turned into information using into information using visual and/or digital image visual and/or digital image processing techniques.processing techniques.

How Far Is Remote?

There is no clear distinction about how great the distance should be. It could be 1 meter, 100 meters, or > 1 million meters.

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NASA 01/15/2009Scientists have discovered methane in Mars' atmosphere, raising the possibility that life might exist on the planet.

A large ice cap found at Mars' northern pole is "of a very high degree of purity," according to an international study reported on 01/20/2009 by French researchers. Image credits: calacademy

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Remote Sensing: Advantages

1. Remote sensing is unobtrusive, i.e., a passive remote sensing does not disturb the object or area of interest.

2. Remote sensing devices are often programmed to collect data systematically (size, time…). This systematic data collection can remove the sampling bias introduced in some in situ investigations.

3. Remote sensing can provide fundamental biophysical data, including: x,y location, z elevation or depth, biomass, temperature, moisture content, etc.

4. Remote sensing can cover large areas and some of the areas are very difficult or impossible in in situ data collection (wetland, forest, desert, …).

Remote Sensing: Advantages

Remote sensingRemote sensing––derived information is now critical to the derived information is now critical to the successful modeling of numerous successful modeling of numerous naturalnatural (e.g., water(e.g., water--supply estimation; supply estimation; eutrophicationeutrophication studies; studies; nonpointnonpoint source source pollution) and pollution) and culturalcultural (e.g., land(e.g., land--use conversion at the use conversion at the urban fringe; waterurban fringe; water--demand estimation; population demand estimation; population estimation) estimation) processes.processes.

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Remote Sensing: Limitations

1. Remote sensing provides some spatial, spectral, and temporal information of value. Data analysis is critical.

2. Human beings designed the sensors to collect data, specify resolutions, calibrate sensors, select platforms that carry sensors, determine when the data will be collected, and specify how the data are processed. Human-induced error will likely be involved.

3. Remote sensing data could be expensive to collect and interpret or analyze.

Fundamental Image Analysis Tasks

• Analog (visual) image processing • Digital image processing• Remote Sensing/GIS and Other Related

Scientific Fields

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In 2004 the US Department of Labor identified geotechnology (including remote sensing, GIS and GPS) as one of the most important emerging and evolving fields, along with nanotechnology and biotechnology.

Education in remote sensing and GIS is becoming as important as fieldwork for new generation of workforce in natural resources management and environmental sciences.