The National Map Seamless Server, Earth Resources Observation and Science (EROS)
MODIS DB NDVI FAQ
Q. What is the MODIS NDVI Direct Broadcast ? A. The Moderate Resolution Imaging Spectroradiometer (MODIS) Direct Broadcast US Normalized Difference Vegetation Index (NDVI) 7-day Composites on The National Map Seamless Server are composites made daily and consist of the 7 most current 7-day passes, then created into a one day composite. The National Map Seamless Server offers the current composite and the previous 6 composites. Earlier composites can be obtained by going to the MODIS Homepage, then link to Obtaining Data. The MODIS is a key instrument aboard NASA's Terra (EOS AM) and Aqua (EOS PM) satellites.Viewing the entire Earth's surface every 1 to 2 days, both Terra and Aqua MODIS data aid in our understanding of global dynamics and processes occurring on the land, in the oceans, and in the lower atmosphere. One of the unique features of the MODIS instrument is its Direct Broadcast (DB) capability of immediately broadcasting the raw data it collects to appropriately equipped ground stations. he MODIS Direct Broadcast offers US NDVI composites acquired from the L1B products. The L1B products for each pass in the most recent 7 days are stripped from the off-nadir pixels at the 500m resolution for bands 1-7. The stripped L1B products (bands 1-7) are resampled to Lambert Azimuthal and tied to lat/long coordinates. UL lat = 48.40 lon= -128.52 Bands 1 (red band) and 2 (NIR band) are used to create an NDVI product for each pass in the 7-day period. The 7-day composite is created for each band (1-7 and NDVI) at the 500m resolution. We loop through each input pass NDVI product and look for the maximum NDVI value. The final composite is ultimately made up of the pixel values that have the maximum NDVI values for each band (1-7 and NDVI). Q.What are the specifications of the MODIS NDVI Direct Broadcast ? A.
Q. What formats are available? A. ArcGrid is an Arc/Info proprietary format. Some other software packages can read the ArcGrid format. Customers who specify ArcGrid will be delivered a workspace. The workspace is not tarred or gzipped. BIL is a non-proprietary format made by running the GRIDIMAGE command in Arc. The data is a simple binary raster format (signed integer data). There is an accompanying ASCII header file that provides file size information (number of rows and columns). The data are stored in row major order (all the data for row 1, followed by all the data for row 2, etc.). TIFF for MODIS DB NDVI is a 32 bit floating point grid format. More information on the 32 bit floating point TIFF is at: Q. What is the coverage area? A. The coverage area is the conterminous US. Q. Where can more information be found about BTS Roads? A. More information concerning MODIS NDVI Direct Broadcast can be found at http://modisdb.usgs.gov/ Also, there is a list of FAQ's at the MODIS website at: http://modisdb.usgs.gov/faq.php Q. Why are some areas "View Only"? A. The areas listed as "VIEW ONLY" are under license restrictions agreements through the contractor or source of the data. |
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://seamless.usgs.gov/faq/modisdb_faq.php
Page Contact Information: webmapping@usgs.gov
Page Last Modified: November 22, 2007
