To measure forests worldwide, satellite imagery has become a practical necessity. Aerial observations are expensive at present and only cover small areas at a time. Ground measurements are also expensive and are logistically challenging and spatially restricted. Neither aerial nor ground observations are well suited to continuous measurement of the entire global forest. Satellite mapping is therefore necessary to detect deforestation and regrowth in remote tropical forests and to track the northern expansion of boreal forests in a warming world. The greatest strengths of satellite‐based measurements are their unparalleled, unbiased measurements, their monthly to daily frequency, and—above all—their synoptic nature. Satellites provide a general view of the whole Earth that is not possible with any other forest measurement method.
In general, satellite technology involves a combination of pixel resolution and image size, with an increase in one dimension requiring a reduction in the other dimension. Coarse‐resolution satellites can generate images of very large areas, but the pixel resolution may be 1,000 meters (m). Conversely, some sensors can render extremely high‐resolution pictures—with pixel sizes less than half a meter—but only over limited areas. Moderate‐resolution satellites, such as those with a pixel size of 30 m and an image width of 185 kilometers (km) are often seen as a good compromise for land mapping.
1990’s - Landsat
Mapping Amazon deforestation during the 1990’s was seen as science at the cutting edge. New reports of rainforest losses were trickling in, creating shock waves around the world. Although the problem of deforestation was known at the time, new satellite-based maps provided a strong incentive for rainforest action. The satellite of choice for deforestation monitoring was the National Aeronautics and Space Administration’s Landsat, and images sold for more than $2,000. It required at least 250 cloud-free Landsat images to make one decent map of the Amazon each year. Only a few elite groups could afford this satellite data, and there were even fewer experts who could convert impenetrable Landsat pixels into user-friendly maps.
2008 – Landsat data made available free to anyone In 2008, both the Brazilian and United States governments made their Landsat archives — all past and future data—completely free to the world. This groundbreaking development meant that anyone could download images using the Internet.
2013 – Landsat 8
In 2013, the National Aeronautics and Space Administration launched Landsat 8, a more advanced system that supports the global forest-monitoring community The Landsat 8 satellite images the entire Earth every 16 days in an 8-day offset from Landsat 7. Data collected by the instruments onboard the satellite are available to download at no charge from GloVis, EarthExplorer, or via the LandsatLook Viewer within 24 hours of reception. Landsat 8 carries two instruments: The Operational Land Imager (OLI) sensor includes refined heritage bands, along with three new bands: a deep blue band for coastal/aerosol studies, a shortwave infrared band for cirrus detection*, and a Quality Assessment band. The Thermal Infrared Sensor (TIRS) provides two thermal bands. These sensors both provide improved signal-to-noise (SNR) radiometric performance quantized over a 12-bit dynamic range. (This translates into 4096 potential grey levels in an image compared with only 256 grey levels in previous 8-bit instruments.) Improved signal to noise performance enable better characterization of land cover state and condition. Products are delivered as 16-bit images (scaled to 55,000 grey levels). Landsat 8 images have a large file size, at approximately 1 GB compressed. Band names, wavelengths and resolution for each sensor are listed on http://landsat.usgs.gov/band_designations_landsat_satellites.php. A comparison of Landsat 8 and Landsat 7 spectral bands and band combinations is available at http://landsat.usgs.gov/L8_band_combos.php (Source: http://landsat.usgs.gov/landsat8.php.
Now - 2016
Today, the forest monitoring world has dramatically changed. Landsat continues to be the most widely used and technologically appropriate satellite for monitoring the world’s forests. With its 30-m by 30-m pixels, Landsat can accurately detect deforestation events down to about one-quarter acre, and it can even be used to monitor subtle forest disturbances, such as clandestine logging and gold mining. The Brazilian government as well as many other governments has made Landsat their choice for mapping their forests.
Source http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3896183/
Copernicus is an European system for monitoring the earth, which became operational in 2012. It consists of a complex set of systems which collect data from multiple sources: earth observation Sentinel satellites and in situ sensors such as ground stations, airborne and sea-borne sensors. It processes these data and provides users with reliable and up-to-date information through a set of services covering six thematic areas:
Copernicus supports a wide range of applications, including environment protection, management of urban areas, regional and local planning, agriculture, forestry, fisheries, health, transport, climate change, sustainable development, civil protection and tourism. (See Copernicus video http://www.copernicus.eu/videos for an overview).
Main components: The Copernicus program consists of three main components:
Management: The Copernicus program is coordinated and managed by the European Commission. The development of the observation infrastructure is performed under the aegis of the European Space Agency for the space component and of the European Environment Agency and the Member States for the in situ component.
Users: The main users of Copernicus services are policymakers and public authorities who need the information to develop environmental legislation and policies or to take critical decisions in the event of an emergency, such as a natural disaster or a humanitarian crisis.
Free access to Copernicus data: The Project database can be accessed without any fee by any one and is available from: http://www.copernicus.eu/project-database
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