Go to the NASS Home Page U.S. Department of Agriculture
National Agricultural Statistics Service
Research and Development Division

of the Director
Census and Survey Research Branch
Data Quality | Statistical Methodology
Geospatial Information Branch
Area Frame | Spatial Analysis

Limitations to AVHRR-based Vegetation Condition Imagery
Main | History | Limitations | Products | Sensors | Formats | Download

CAUTION: Comparing images from year to year requires a knowledge of crop phenology for both years. These images are not yet used in a quantitative way by the Agricultural Statistics Board in setting official USDA estimates. A white paper titled ' Limited Use of Remotely Sensed Data for Crop Condition Monitoring and Crop Yield Forecasting in NASS' describes this in more detail.

USDA/NASS and USDA/ARS have been studying the properties of NDVI based images for several years through a cooperative research agreement. The user will sometimes see anomalies caused by atmospheric effects when reviewing the same area across several periods. When a large area is cloud covered, many of the surrounding data values may also be affected, especially when looking at ratio based products. Scene edges can also cause visual differences within composite scenes that are not really there.

For more information about this topic or about the NASS Spatial Analysis Research Section (SARS), contact the GeoSpatial Information Branch at HQ_RDD_GIB@nass.usda.gov.

Available Years (Return to Standard Graphics Products)
NOAA-18: 2011 2010
NOAA-17: 2009 2008 2007 2006 2005 2004
NOAA-16: 2003 2002 2001
NOAA-14: 1999 1998 1997 1996 1995

Growing Season Animations | National Crop Progress

Back | NASS Home| USDA Home| USDA Remote Sensing Page