Remote sensing

Manual remote sensing with aerial photographs of Hamburg (1943)

The term remote sensing describes the entirety of the processes for obtaining information about the earth's surface or other objects that are not directly accessible by measuring and interpreting the electromagnetic or sound waves emanating or reflected from them .

In contrast to other recording methods, which require direct access to the object to be examined or observed, remote sensing means the contact-free exploration of the earth's surface including the earth's atmosphere . This is for example by airplane - or satellite -getragene sensors enables ( remote sensors such as cameras or scanners ). Occasionally, however, “ drones ” or balloons are also used as platforms. Remote sensing is assigned to photogrammetry and satellite geodesy . In contrast, planetology and astronomy are not assigned to remote sensing, although remote sensing sensors are also used here.

For remote sensing, passive or active systems are used, whereby wide areas of the electromagnetic spectrum can be evaluated. Passive systems record the solar radiation reflected from the earth's surface ( e.g. multispectral camera ) as well as the natural radiation emitted by the earth's surface ( e.g. thermal imaging camera ). In contrast to this, active systems emit microwave or laser beams and receive their reflected components (for example radar systems and laser altimeters ).

Remote sensing data are particularly important in the geosciences and geography , since global observation of the earth's surface and atmosphere with high spatial resolution is only possible with the aid of remote sensing sensors. In addition to the synoptic overview of large rooms, satellite-based remote sensing sensors also enable repeated (sometimes daily) coverage of one and the same area.

history

Historic aerial camera (around 1950)

Remote sensing has its origins in military reconnaissance . From a mostly high point (mountain) one tried to observe the movements of the opponent. With the beginning of aviation , the representation changed from perspective to a top view from above. Initially, tethered balloons with human observers and a drawing pad were used, later airplanes with aerial cameras. The aerial photography could be evaluated relatively early, but the result was always strongly dependent on the evaluator. The data obtained today with satellite platforms and various image recording devices and spectral scanners can be manipulated and processed with computer systems ( digital image processing ). This systematic evaluation has been greatly improved in recent years. Nevertheless, visual image interpretation remains important even today .

Remote sensing sensors

Both passive and active systems are used in remote sensing, whereby wide areas of the electromagnetic spectrum can be evaluated.

The most common types of sensors are:

• Multispectral camera
• Thermal imaging cameras
• Radar systems
• Hyperspectral sensors
• Microwave radiometer
• Laser altimeter
• Interferometer
• Aerial camera

Remote sensing satellites

There are a large number of satellites in orbit . Depending on the area of ​​responsibility, these are also divided into environmental satellites and weather satellites ; however, the transitions between the two categories are fluid.

The main government and commercial earth observation satellites are

• (semi) state:
  • Envisat , ( ESA , Europe)
  • ERS , (ESA, Europe)
  • Landsat , ( NASA , USA)
  • SPOT , ( CNES , France)
  • IRS , ( ISRO , India)
  • Earth Observing System (EOS) , (NASA, USA), u. a. Terra and Aqua
  • TerraSAR-X , ( DLR , Germany)
  • TanDEM-X , (DLR, Germany)
  • Sentinel , ( ESA , Europe)
• commercially:

1. DigitalGlobe (4 WorldView , GeoEye-1 )
2. Airbus Defense and Space ( SPOT 6 & 7, 2 Pléiades )
3. Planet Labs with Terra Bella (87 Dove small satellites, 5 RapidEye , 5 SkySat )
4. BlackSky Global ( Pathfinder-1 and -2)

The list of earth observation satellites lists many more satellites. The satellites listed have a wide variety of spectral, spatial, temporal, optical and radiometric resolutions .

Areas of application

In accordance with the diversity of the earth's habitat, the field of application for modern remote sensing is very diverse. Remote sensing is used in a wide variety of disciplines thanks to the unique ability to capture large areas with high temporal and spatial resolution.

• Earth sciences , geography , cartography and geodesy
  • Elevation relief and waterways
  • Geology (rock types, deposits)
  • Land cover, land use and land management
  • Urbanization (urban expansion)
  • Forestry (inventories, wood potential assessments, forest damage mapping, road construction planning, etc.)
  • Agriculture (harvest forecasts, cultivation areas, review of subsidized fallow land, precision farming, etc.)
  • Vegetation phenology (sequence of aspects)
• Civil protection
  • Forest fires (extent of destruction)
  • Volcanic eruptions (prediction and monitoring)
  • Earthquake (change in altitude)
  • Drought monitoring
  • Environmental pollution (oil discharge into the world's oceans)
• Climatology , meteorology and oceanography
  • Weather forecast
  • Climate monitoring
  • Swell measurement (surface waves, currents)
• Atmospheric physics and chemistry
  • Trace gases, clouds, aerosols
  • Temperature, air pressure
  • Radiation budget, radiation budget
  • Monitoring of emissions, e.g. B. carbon dioxide
• archeology
  • Archaeological flight prospecting
  • Mapping of excavations
• Arms control
  • Verification of disarmament agreements
• Human rights
  • Before and after comparison of large-scale destruction

Classification and subdivision

According to scope

Remote sensing data are used in many geoscientific disciplines. Remote sensing is further subdivided accordingly.

Breakdown of remote sensing by area of ​​application

• Soil science remote sensing
• Agricultural remote sensing
• Botanical / vegetation remote sensing
• Forestry remote sensing
• Geological remote sensing / photogeology
• Hydrological remote sensing
• Oceanographic remote sensing
• Limnological remote sensing
• Urban remote sensing / urban remote sensing
• Environmental remote sensing (remote sensing environmental monitoring)
• Climatological / meteorological remote sensing
• Atmospheric remote sensing
• Archaeological remote sensing / aerial archeology
• Geodetic remote sensing / satellite geodesy
• Photogrammetry

According to measuring method

Remote sensing data are collected in a wide variety of wavelength ranges and with different measurement methods. Remote sensing can be subdivided accordingly.

Subdivision of remote sensing according to measurement method

• Photogrammetry and aerial photo measurement
• Spectral remote sensing in optical wavelength ranges (UV, VIS, IR). Remote sensing of finely ramified bodies of water makes use of the fact that the reflective reflections make them stand out from land surfaces, which allows spectral evaluation even if the image resolution is insufficient to resolve the course of the bank.
• Passive microwave remote sensing, radiometry
• Active microwave remote sensing (radar)
• Laser altimetry
• Interferometry (radar interferometry)

According to evaluation method

To provide area-differentiated geodata, remote sensing data are processed using different evaluation methods. The remote sensing can be further subdivided depending on the selected evaluation method.

Subdivision of remote sensing according to evaluation method

• Remote sensing classification and segmentation
• Remote sensing time series analysis
• Empirical-statistical (chemometric) analysis of remote sensing data
• Remote sensing radiation transfer modeling
• Remote sensing model inversion (inversion of radiation transfer models)
• Assimilation of remote sensing data into process-oriented (dynamic) models
• Remote sensing separation processes
• Remote sensing change detection (Engl. Detection Change )
• Image spectroscopy
• Aerial image interpretation and visual interpretation of remote sensing data
• Aerial image measurement and photogrammetric methods (stereophotogrammetry)

Methods

In the analysis of analog and digital remote sensing data, a large number of methods and procedures are used, which are listed in key words below. In addition, there are geoscientific work steps related to the recording of reference measurements in the field (not listed). From the list it becomes clear to what extent remote sensing is a methodological science.

• Methods of digital image processing
  • Data preparation for visual interpretations (e.g., contrast spreading , color saturation )
  • Transformations of the color space
  • Feature extraction and pattern recognition
  • Monitored and unsupervised classification and segmentation processes (including cluster processes , maximum likelihood classifiers , support vector machines , Kohonen networks )
  • Geometrical corrections , geometrical rectification and rectification
  • Radiometric and atmospheric corrections
  • Filter method in the spatial and frequency domain (including Fourier analysis )
  • Texture analysis
• Statistical and chemometric methods
  • Regression analysis
  • multiple and stepwise multiple regression
  • Partial Least Squares Estimation
  • Principal component regression ( English Principal Component Regression , short PCR )
  • Discriminant analysis
  • Statistical test planning ( English design of experiments )
• Geostatistical methods
  • Interpolation methods (including kriging and co-kriging )
• Methods of time series analysis and signal processing
  • Trend analysis
  • Remote sensing change detection / change detection
  • Method for filtering time series ( e.g. , Maximum Value Compositing and Savitzky-Golay Filter , Splines )
• Learning procedures and procedures of artificial intelligence
  • Artificial Neural Networks
  • Genetic Algorithms
  • Optimization procedure
• Radiative transfer modeling and mathematical modeling
  • Development of physically based radiation transfer models
  • Inversion of radiation transfer models
  • Spectral Entmischungsverfahren ( English spectral unmixing )
  • Sensitivity analysis
  • Computer simulation
• Assimilation process
  • Kalman filter
  • Recalibration and reinitialization procedures for dynamic process models
• Geoinformatics method
  • GIS analyzes (including intersections, buffering , topology analyzes )
  • Morphological image processing
  • Data mining
• Laboratory and field spectroscopy
  • Spectroscopic measurements
• Process of visual image interpretation
  • Image address
  • Texture address
  • Image interpretation
  • Stereo image interpretation
• Photogrammetric methods
  • Image measurement
  • Stereo photogrammetry

didactics

Attempts are made to integrate the topic of remote sensing into school lessons . This can involve the integration of remote sensing data, such as photographic, digital or microwave-based aerial and satellite images, or remote sensing methods, such as resampling, classification of land surfaces and time series analyzes, as didactic aids.

There are different learning platforms / learning modules (e.g. FIS, geospektiv or YCHANGE) for use in schools. In addition to other software, the virtual globe Google Earth or the geographic information system QGIS are used .

literature

• Christian Heipke (Ed.): Photogrammetry and remote sensing: Handbook of Geodesy, edited by Willi Freeden and Reiner Rummel . 1st edition. Springer Spectrum, Heidelberg 2017, ISBN 3-662-47093-4 .
• J. Albertz: Introduction to Remote Sensing. Basics of the interpretation of aerial and satellite images. Scientific Book Society, Darmstadt 2001, ISBN 3-534-14624-7 .
• Jörg Bofinger : Airplane, laser, probe, spade. Remote sensing and archaeological field research using the example of the early Celtic princely seats . Regional Council Stuttgart, State Office for Monument Preservation, Esslingen a. N. 2007 (German, English, denkmalpflege-bw.de [PDF; 5.8 MB ; accessed on December 13, 2010]).
• E. Löffler, U. Honecker, E. Stabel: Geography and remote sensing. An introduction to the geographic interpretation of aerial photographs and modern remote sensing data. Borntraeger, Berlin 2005, ISBN 3-443-07140-6 .
• Chandra P. Giri: Remote Sensing of Land Use and Land Cover: Principles and Applications. CRC Press, 2012, ISBN 978-1-4200-7074-3 .
• Bruce A. Campbell: Radar remote sensing of planetary surfaces. Cambridge Univ. Press, Cambridge 2002, ISBN 0-521-58308-X .
• Floyd F. Sabins: Remote sensing - principles and interpretation. Freeman, New York 2000, ISBN 0-7167-2442-1 .
• David L. Verbyla: Satellite remote sensing of natural resources. Lewis Publ., Boca Raton 1995, ISBN 1-56670-107-4 .
• Sarah H. Parcak: Satellite remote sensing for archeology. Routledge, London 2009, ISBN 978-0-415-44877-2 .
• Alexander D. Kowal, Lew Dessinow: Into space for the benefit of mankind. Progress Moscow publishing house, Staatsverlag der DDR Berlin, 1987, ISBN 3-329-00515-7 .
• Rosa Lasaponara, Nicola Masini: Satellite Remote Sensing - A new tool for Archeology. In: Remote Sensing and Digital Image Processing Series. 16. Springer, 2012, ISBN 978-90-481-8801-7 .
• H. Taubenböck, M. Wurm, T. Esch & S. Dech (Eds.): Global Urbanization - Perspective from Space. Springer, Berlin / Heidelberg 2015, ISBN 978-3-662-44841-0 .

Web links

Commons : Remote Sensing  - collection of images, videos and audio files

• Introduction to digital remote sensing methodology in geosciences (University of Münster)
• GISWiki - remote sensing websites
• Kurt Baldenhofer: Lexicon of remote sensing.

Individual evidence

1. ^ Robinson Meyer: A New 50-Trillion-Pixel Image of Earth, Every Day . In: The Atlantic . March 9, 2016 ( theatlantic.com ).
2. ↑ Airbus Defense and Space Invests in Very High-Resolution Satellite Imagery from 2020 Onwards ( Memento from February 7, 2017 in the Internet Archive ), September 15, 2016
3. ↑ Axel Relin, Rupert Haydn: Remote sensing control of agriculturally used areas . In: Geosciences . tape 12 , no. 4 , 1994, ISSN  0933-0704 , pp. 98-102 , doi : 10.2312 / geosciences . 1994.12.98 .
4. ↑ eyesondarfur.org ( Memento from June 10, 2008 in the Internet Archive )
5. ↑ Vern Vanderbilt et al .: Impact of pixel size on mapping surface water in subsolar imagery . In: Remote Sensing of Environment . tape 109 , no. 1 , July 12, 2007, ISSN  0034-4257 , p. 1-9 , doi : 10.1016 / j.rse.2006.12.009 ( researchgate.net ).
6. ↑ Remote sensing in schools , uni-bonn.de, accessed on October 28, 2010.
7. ↑ fis.uni-bonn.de
8. ↑ geospektiv.de
9. ↑ ychange.eu