Remote sensing

In current usage, the term remote sensing generally refers to the use of satellite- or aircraft-based sensor technologies to detect and classify objects on Earth.

Active collection, on the other hand, emits energy in order to scan objects and areas whereupon a sensor then detects and measures the radiation that is reflected or backscattered from the target.

RADAR and LiDAR are examples of active remote sensing where the time delay between emission and return is measured, establishing the location, speed and direction of an object.

Remote sensing also replaces costly and slow data collection on the ground, ensuring in the process that areas or objects are not disturbed.

Orbital platforms collect and transmit data from different parts of the electromagnetic spectrum, which in conjunction with larger scale aerial or ground-based sensing and analysis, provides researchers with enough information to monitor trends such as El Niño and other natural long and short term phenomena.

Other uses include different areas of the earth sciences such as natural resource management, agricultural fields such as land usage and conservation,[5][6] greenhouse gas monitoring,[7] oil spill detection and monitoring,[8] and national security and overhead, ground-based and stand-off collection on border areas.

Object-Based Image Analysis (OBIA) is a sub-discipline of GIScience devoted to partitioning remote sensing (RS) imagery into meaningful image-objects, and assessing their characteristics through spatial, spectral and temporal scale.

One of the best systems for archiving data series is as computer-generated machine-readable ultrafiche, usually in typefonts such as OCR-B, or as digitized half-tone images.

The regular spatial and temporal organization of Level 3 datasets makes it feasible to readily combine data from different sources.

Satellite images provide very useful information to produce statistics on topics closely related to the territory, such as agriculture, forestry or land cover in general.

[35] Forest area and deforestation estimation have also been a frequent target of remote sensing projects,[36][37] the same as land cover and land use[38] Ground truth or reference data to train and validate image classification require a field survey if we are targetting annual crops or individual forest species, but may be substituted by photointerpretation if we look at wider classes that can be reliably identified on aerial photos or satellite images.

For agricultural statistics, field surveys are usually required, while photo-interpretation may better for land cover classes that can be reliably identified on aerial photographs or high resolution satellite images.

[53] This is demonstrated by the first line of a 1941 textbook titled "Aerophotography and Aerosurverying," which stated the following: "There is no longer any need to preach for aerial photography-not in the United States- for so widespread has become its use and so great its value that even the farmer who plants his fields in a remote corner of the country knows its value.

[54] A more recent development is that of increasingly smaller sensor pods such as those used by law enforcement and the military, in both manned and unmanned platforms.

[55] The development of artificial satellites in the latter half of the 20th century allowed remote sensing to progress to a global scale as of the end of the Cold War.

[56] Instrumentation aboard various Earth observing and weather satellites such as Landsat, the Nimbus and more recent missions such as RADARSAT and UARS provided global measurements of various data for civil, research, and military purposes.

Space probes to other planets have also provided the opportunity to conduct remote sensing studies in extraterrestrial environments, synthetic aperture radar aboard the Magellan spacecraft provided detailed topographic maps of Venus, while instruments aboard SOHO allowed studies to be performed on the Sun and the solar wind, just to name a few examples.

[59][60] With assistance from her fellow staff member at the Office of Naval Research, Walter Bailey, she coined the term "remote sensing".

Furthermore, remote sensing exceedingly influences everyday life, ranging from weather forecasts to reports on climate change or natural disasters.

Remote sensing only plays a tangential role in schools, regardless of the political claims to strengthen the support for teaching on the subject.

In fact, the subject of remote sensing requires a consolidation of physics and mathematics as well as competences in the fields of media and methods apart from the mere visual interpretation of satellite images.

Many teachers have great interest in the subject "remote sensing", being motivated to integrate this topic into teaching, provided that the curriculum is considered.

Examples include: FIS – Remote Sensing in School Lessons,[68] Geospektiv,[69] Ychange,[70] or Spatial Discovery,[71] to promote media and method qualifications as well as independent learning.

A large number of proprietary and open source applications exist to process remote sensing data.

[74] The United States Army Ballistic Missile Agency launched the first American satellite, Explorer 1, for NASA's Jet Propulsion Laboratory on January 31, 1958.

The Earth observation satellites ERS-1, ERS-2 and Envisat of European Space Agency as well as the MetOp spacecraft of EUMETSAT are all operated at altitudes of about 800 km (500 mi).