MODIS (Moderate Resolution Imaging Spectrometer) is an imaging instrument flying on two satellites in NASA’s Earth Observing System; Terra and Aqua. Launched in 1999, Terra orbits from south to north with a morning equatorial crossing. Launched in 2002, Aqua orbits from north to south with an afternoon equatorial crossing. Flying on two satellites allows it to image the same area at different times of the day as well as cover the entire earth in one or two days. Its coarse spatial resolution is designed to observe land, ocean, and atmospheric conditions at a regional and global scale. The system has 36 separate spectral bands and a field of view ±55° off-nadir which gives it the ability to have very large swath widths of 2,330 km. The bands most applicable for rangeland studies would be bands 1-7 which gather data in the visible and infrared range at a spatial resolution of 250 meters and 500 meters.
A major advantage of using MODIS imagery is the availability of a suite of products ranging from raw images to highly processed products such as vegetation indices. The products are made on varying temporal schedules, some of which are made as often as daily and every 8 days. The products are all archived and available, usually at no charge. MODIS products are organized into different processing levels. Level 0 products are raw digital number images. Level 1 products include uncalibrated and calibrated radiance values. Level 2 and 3 products have more processing and are derived from lower level products.
links are to other methods guide abstracts, not to specific MODIS products
Image source: Steven Running, MODIS Land Group Member, University of Montana
This is a composite image of the United States taken by MODIS between March 24 and April 8, 2000. The image shows the Fraction of Photosynthetically Active Radiation that was absorbed by land vegetation for photosynthesis.
MODIS is in a sun-synchronous orbit meaning it crosses over any given latitude at the same time each day. It flies at an altitude of 705 km and covers the entire Earth in 1-2 days. It has a swath width of 2,330 km and 12-bit radiometric_resolution meaning it can distinguish radiation in 4096 different levels for each band.
Edit the following table or delete it and provide a description of spectral characteristics
|Band||Resolution||Wavelength µm||Band Utility|
|1||250m||0.620-0.670||Land-cover classification, clorophyll|
|2||250m||0.841-0.876||absorbtion, leaf area index mapping|
|4||500m||0.545-0.565||Land, cloud, and aerosol properties|
|8||1km||0.405-0.420||Ocean color, phytoplankton, and|
|16||1km||0.862-0.877||Atmospheric water vapor|
|19||1km||0.915-0.965||Surface and cloud temperature|
|30||1km||9.580-9.880||Surface and cloud temperature|
MODIS products are available from several sources and usually free to the public.
MODIS Level 1 and atmosphere products are available through the Level 1 and Atmospheric Archive and Distribution System ( LAADS). http://ladsweb.nascom.nasa.gov/ Level 1 products include raw radiance and calibrated radiance images. Raw digital number images are also available through order. All of the images in their archive are free of charge.
Level 2 and 3 Land Products are available through Nasa’s Warehouse Inventory Search Too (WIST) and the Land Processes Distributed Active Archive Center (LPDAAC) Data Pool at the U. S. Geological Survey EROS Data Center (EDC). https://lpdaac.usgs.gov/get_data Examples of level 2 and 3 products are land cover, leaf area index, surface temperature, and burned area. All products on a specific temporal schedule are archived and available free of charge to the general public. Detailed instructions on how to acquire MODIS data through the LPDAAC Data Pool are here: https://lpdaac.usgs.gov/sites/default/files/public/get_data/docs/DP_Tutorial.pdf.
Another source for MODIS data is the Global Land Cover Facility. http://www.landcover.org/data/modis/ They offer several vegetation products made from 16-day and 32-day composite images. The products come in a GeoTIFF format which can be easier to work with in a geographic information system.
MODIS data from NASA/USGS are distributed in the Hierarchical Data Format (HDF-EOS). This format can be reprojected or converted into other formats such as GeoTiff, but in the past HDF-EOS has been notoriously difficult to work with. Recent versions of ArcGIS (e.g., version 9.3) can read the HDF-EOS format. A listing of some other tools that can be used to view and convert HDF-EOS images can be found at https://lpdaac.usgs.gov/tools, but be cautioned that most of these tools are not easy to implement.
Java is required for viewing and selecting data in the LPDAAC Data Pool.
MODIS images can be converted into GeoTiff format making is compatible with ESRI ArcGIS and other GIS platforms. The images can be manipulated and processed in remote sensing software packages such as ENVI and ERDAS Imagine.
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