3. Resolution

Spatial resolution

Satellite sensors store information about objects as a grid. Digital data is collected from the area covered in the form of individual image points, so called pixels. A pixel is the smallest area unit in a digital image.

The size of the pixel is dependent on the sensor type and determines the resolution of the image. The measurement of the resolution is the edge length of a pixel. The higher the resolution and the finer the grid is, the larger is the degree of recognizable details on the earth's surface.

The resolutions of today's satellite systems vary from a few centimetres (for example military usage) to kilometres. Application:

• Low resolution: larger than 30 m
• Medium resolution: 2 - 30 m
• High resolution: under 2 m

Low Medium 1 Medium 2 Medium 3 High resolution

Low resolution of Western Europe - METEOSAT (1km).
Source: Copyright 2005 EUMETSAT

Different satellites are designed and launched based on their intended use and orbit.

• A lower resolution usually coincides with a higher repetition rate, meaning that within a short interval (METEOSAT-8
  

  Source: NASA.

  EUMETSAT operates a fleet of meteorological satellites and their related ground systems to deliver reliable and cost-efficient data, images and products. These in turn fulfil requirements for weather and climate monitoring, primarily of national meteorological services in the Member- and Cooperating States.
  Meteosat Second Generation (MSG) is a significantly enhanced follow-up system to the previous generation of Meteosat. The first MSG satellite launched was Meteosat-8 in 2002. A second satellite followed in December 2005.

  Official web page:http://www.eumetsat.int/

  for example every 15 min) the satellite investigates the same area. A "coarse" resolution is used to record large or global areas for climate-related enquiries, for example the radiation budget of the earth and for weather monitoring. Additionall applications include earth observation of land use and oceans, the ocean's ice cover and the surface temperatures.
• Satellites with medium resolution such as LANDSAT 7
  

  Source: satimagingcorp.com.

  The Landsat Program is a series of earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey. Since 1972, Landsat satellites have collected information about earth from space.
  The government-owned Landsat 7 was successfully launched on April 15, 1999. The earth observing instrument on Landsat 7, the Enhanced Thematic Mapper Plus (ETM+), replicates the capabilities of the highly successful Thematic Mapper instruments on Landsats 4 and 5.

  Official web page:http://landsat.gsfc.nasa.gov/

  are used for the global observation of land surfaces. Tropical rainforests and their deforestation have been observed by the LANDSAT satellites for more than 30 years.
• High resolution data is mainly used for smaller areas of the earth's surface. Only recently such data has become available commercially and privately. Satellites such as IKONOS
  

  Source: satimagingcorp.com.

  The IKONOS Satellite is a high-resolution satellite operated by GeoEye. Its applications include both urban and rural mapping of natural resources and of disasters, tax mapping, agriculture and forestry analysis, mining, engineering, construction, and general changes. Its high resolution data makes an integral contribution to homeland security, coastal monitoring and facilitates 3D terrain analysis.

  IKONOS web page:http://www.satimagingcorp.com/satellite-sensors/ikonos.html

  or QuickBird
  

  Source: satimagingcorp.com.

  QuickBird is a high resolution satellite owned and operated by DigitalGlobe. The satellite is an excellent source for environmental data with respect to the analysis of changes in land usage, agricultural and forest climates. QuickBird's imaging capabilities can be applied to a host of industries, including oil and gas exploration & production (E&P), engineering and construction and environmental studies.

  QuickBird web page:http://www.satimagingcorp.com/satellite-sensors/quickbird.html

  send data for topographic and thematic mapping of for example land use, vegetation, or as planning resources for cities, large projects etc. Information can also be "ordered" in advance, because the turning of the satellite sensors can reduce the repeat rates and can monitor the desired areas earlier (Albertz 2007, Löffler et al. 2005).

Spatial resolution.
Source: Satellite Imaging Corporation