contributed by Jeffrey Gillan. Edited by Leandro Gonzalez
SPOT HRV, HRVIR
Agency/Company Operating the Sensor
Commercially operated by the Spot Image Corporation
The SPOT program is a series of Earth observing satellites launched by the French Centre National d’Etudes Spatiales (CNES), in cooperation with Belgium and Sweden. Since 1986, five SPOT satellites have been launched and three are still currently operational. SPOT 1, 2, and 3 have carried the High Resolution Visible sensor which has 3 color bands and a panchromatic band imaging the Earth at a moderate spatial resolution (20m and 10m). SPOT 4 carries the High Resolution Visible and Infrared sensor which is essentially the same as its predecessor with an extra infrared band. SPOT 5 was a leap forward in terms of spatial resolution capabilities. The color bands have an IFOV of 10m while the panchromatic band has an IFOV of 2.5m.
Unlike similar sensors such as Landsat TM, SPOT has the ability to gather data off-nadir which significantly reduces the revisit time of any geographic area. Because there are three satellites operational, the SPOT program can image any place on Earth every day. This is a huge advantage when you need to track fast changing conditions or get cloud free images.
Another major advantage of SPOT imagery is their geometric accuracy. The 10m panchromatic data accuracy rivals that of aerial photography and can serve as GIS base layers and orthophoto maps.
SPOT is commercially operated and thus the imagery can carry high costs. A vast suite of products is available with prices ranging from $1,700 to $11,000 depending on the size, resolution, and processing level.
One limitation of SPOT imagery is the size of the scenes. The standard scene is 60 km x 60 km which is much smaller than a standard Landsat TM scene (170 km x 185 km). Conducting a study over a large area may require more scenes, and thus more cost.
|SPOT 1||February 21, 1986|
|SPOT 2 (still operational)||January 22, 1990|
|SPOT 3||September 25, 1993|
|SPOT 4 (still operational)||March 24, 1998|
|SPOT 5 (still operational)||May 3, 2002|
The following products are standard products offered. Please see the SPOT Imaging Corporation (http://www.spot.com) for all product information.
- SPOT Scenes: The standard products intended for an image processing specialist. They come in several processing levels.
- SPOT Views: Scenes with higher processing ready for direct use in a GIS
- SPOTMaps – Orthorectified gis-ready image that are mosaiced to fit an area of interest
- Digital Elevation Models with 30m spatial resolution
Each SPOT satellite has a pair of sensors that can independently image the Earth. The images are collected in 8 bit radiometric resolution (0-255).
|Pan (SPOT 4)||2.5m||0.48-0.71||Panchromatic|
|SWIR (SPOT 4)||20m||1.58-1.75||Short wave infrared|
Image footprint or swath width
The system consists of two sensors with a combined 117 km swath width when the sensors are pointed at nadir. Each individual sensor is has a 60 km swath width. Using a mirror, the sensors can be pointed off-nadir up to 50.5° (950 km) from the orbital track center line. A Spot full image scene is 3,600 km2
SPOT satellites are in a sun synchronous orbit at an altitude of 822 km. At nadir, the return interval is 26 days. With the capability of pointing the sensors off-nadir, the revisit time can be 1 to 4 days depending on the latitude. Thanks to the constellation of SPOT satellites, it is possible to image any place on Earth each day.
Cost, Acquisition, Licensing
Images from 1986 to present are available for purchase. SPOT are tasking satellites meaning they acquire images on demand and may not have every location and date in their image archive. All images can be ordered on-line from SPOT Image Corporation at http://www.spot.com/
Prices vary depending on the level of processing, spatial resolution, and scene size. Prices range from $1,700 per scene to $11,000 per scene. Requesting a new acquisition could carry an additional fee of a few thousand more dollars. Consult this document for detailed information on pricing.
SPOT images can also be purchased through one of its many resellers. http://www.astrium-geo.com/en/34-commercial-network.
Because SPOT is commercially operated, there are some licensing restrictions regarding image usage and sharing. Please consult with SPOT to get the level of licensing that is appropriate for your research or project.
SPOT images come in DIMAP format which works just like GeoTIFF. Alternatively, products can be delivered in KML format making it compatible with Google Earth.
Examples of Rangeland Uses
- Fabricius et al. (2004) used SPOT imagery to investigate whether or not protected rangelands had higher patch diversity than unprotected lands.
SPOT images usually come in a user friendly GeoTIFF format, which is preferred because of its easy integration with GIS platforms like ArcGIS and image processing programs such as Erdas Imagine and ENVI.
- SPOT Wikipedia page http://en.wikipedia.org/wiki/SPOT_(satellites)
- Fabricius, C., A. R. Palmer, and M. Burger (2004), Landscape diversity in a conservation area and commercial and communal rangeland in Xeric Succulent Thicket, South Africa, Landscape Ecology, Vol. 17, no. 6, pp. 531-537.
- Jensen, John R. (2007), Remote Sensing of the Environment: An Earth resource perspective, second edition, Prentice Hall series in geographic information science, Upper Saddle River, NJ.