No. 53, May/June 2003
Using geospatial technologies to develop
participatory tools for natural resources management
The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument was first launched on the Terra satellite in December 1999. A second MODIS instrument was successfully launched with the Aqua satellite in May 2002. Terra's orbit around the Earth is timed so that it passes from north to south across the equator in the morning (10:30 AM), while Aqua passes south to north over the equator in the afternoon (1:30 PM). MODIS belongs to a new generation of sensors that collect data across a wide spectral range with moderate spatial resolution (250m-1km) and near daily global coverage. MODIS images the Earth with a swath width of 2,330 km in 36 spectral bands or channels ranging in wavelength from 0.405 to 14.385 µm. It takes measurements at three spatial resolutions: 250 m, 500 m, and 1,000 m.
MODIS Spectral Characteristics | |||
---|---|---|---|
Band # | Wavelength range | Spatial resolution | Primary use |
1 |
620 - 670 nm | 250 m | Land/cloud/aerosols boundaries |
2 |
841 - 876 nm | 250 m | |
3 |
459 - 479 nm | 500 m | Land/cloud/aerosols properties |
4 |
545 - 565 nm | 500 m | |
5 |
1230 - 1250 nm | 500 m | |
6 |
1628 - 1652 nm | 500 m | |
7 |
2105 - 2155 nm | 500 m | |
8 |
405 - 420 µm | 1,000 m | Ocean color/phytoplankton/biochemistry |
9 |
438 - 448 µm | 1,000 m | |
10 |
483 - 493 µm | 1,000 m | |
11 |
526 - 536 µm | 1,000 m | |
12 |
646 - 556 µm | 1,000 m | |
13 |
662 - 672 µm | 1,000 m | |
14 |
673 - 683 µm | 1,000 m | |
15 |
743 - 753 µm | 1,000 m | |
16 |
862 - 877 µm | 1,000 m | |
17 |
890 - 920 µm | 1,000 m | Atmospheric water vapor |
18 |
931 - 941 µm | 1,000 m | |
19 |
915 - 965 µm | 1,000 m | |
20 |
3.660 - 3.840 µm | 1,000 m | Surface/cloud temperature |
21 |
3.929 - 3.989 µm | 1,000 m | |
22 |
3.929 - 3.989 µm | 1,000 m | |
23 |
4.020 - 4.080 µm | 1,000 m | |
24 |
4.433 - 4.080 µm | 1,000 m | Atmospheric temperature |
25 |
4.482 - 4.549 µm | 1,000 m | |
26 |
1.360 - 1.390 µm | 1,000 m | Cirrus clouds/water vapor |
27 |
6.535 - 6.895 µm | 1,000 m | |
28 |
7.175 - 7.475 µm | 1,000 m | |
29 |
8.400 - 8.700 µm | 1,000 m | Cloud properties |
30 |
9.580 - 9.880 µm | 1,000 m | Ozone |
31 |
10.780 - 11.280 µm | 1,000 m | Surface/cloud temperature |
32 |
11.770 - 12.270 µm | 1,000 m | |
33 |
13.185 - 13.485 µm | 1,000 m | Cloud top altitude |
34 |
13.485 - 13.785 µm | 1,000 m | |
35 |
13.785 - 14.085 µm | 1,000 m | |
36 |
14.085 - 14.385 µm | 1,000 m |
Numerous MODIS data products are generated for study of land-based systems, including two vegetation indices, NDVI and the Enhanced Vegetation Index (EVI) (for more information see http://modis-land.gsfc.nasa.gov). MODIS data have been available since 2000, but the experimental nature both of the sensor and of the generation of value-added products like vegetation indices makes the data processing stream less systematic (and therefore more of a challenge to automate) than AVHRR. For purposes of the RangeView web site, the Arizona Remote Sensing Center (ARSC) obtains MODIS data and value-added products through the EOSDIS Distributed Active Archive Centers (DAACs) and their recently instituted Data Pools. The data are made available in 1200 by 1200 km tiles that cover the globe; however, RangeView is currently focusing on the six tiles which cover the southwestern U.S. and northern Mexico. Though processed differently than AVHRR data, many of the MODIS products are composited images with one image representing the entire composite period (8 and 16 days). The products currently in use or proposed for future use in RangeView, their corresponding composite periods, spatial resolutions, and geographic coverage areas are listed below.
Some MODIS Land Products | |||
---|---|---|---|
Modis product | Composite period | Spatial resolution | Coverage area |
Vegetation indices (NDVI, EVI) | 16-day | 1,000 m | Southwest US & northern Mexico |
Vegetation indices (NDVI, EVI) | 16-day | 250 m | Arizona |
Land cover/Land* Cover Change | 96-day | 1,000 m | Southwest US & northern Mexico |
Thermal anomalies, fires, biomass burning* | 8-day | 1,000 m | Southwest US & northern Mexico |
Leaf Area Index (LAI) and FPAR* | 8-day | 1,000 m | Southwest US & northern Mexico |
Net photosynthesis and Primary Productivity* | 8-day | 1,000 m | Southwest US & northern Mexico |
*Proposed for RangeView in the future |
The Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI; a vegetation index tailored to maximize MODIS spectral capabilities) are the principal products currently used in this project. In addition to the vegetation indices acquired from EOS, ARSC produces several products from the NDVI and EVI data using in-house image processing protocols. These include difference from previous period and difference from previous year for both NDVI and EVI. ARSC is also actively pursuing data continuity research in an attempt to make the most of the long-term nature of the AVHRR data set relative to MODIS products.
MODIS data may be ordered through the EROS Data Center's Earth Observing
System Data Gateway at http://edcimswww.cr.usgs.gov/pub/imswelcome/.
See
MODIS Web (http://modis.gsfc.nasa.gov/),
TERRA (http://terra.nasa.gov/), or
AQUA (http://aqua.gsfc.nasa.gov/)
for more information.
Sidebar material adapted from the RangeView Glossary (http://rangeview.arizona.edu/glossary/glossary.html/)