Please note: Recent updates to MODIS processing can affect inter-annual comparisons.

NASA and the USGS are in the process of updating MODIS with new processing algorithms that incorporate lessons learned from past applications of MODIS products. Rangeview incorporates the latest version (collection 5) into the Dynamic Animation Tool starting in 2007. Data from 2000 through 2006 will remain as collection 4 data until the Collection 5 reprocessing of the historical data has been completely finished and made available from the USGS. The vegetation products have changed slightly between the two collections, which means that comparisons between years must be done with care. This will be important when looking at two years side by side in the viewers, and when interpreting the difference from average and difference from last year images. The shift in the values is extremely small, and will most likely be unnoticeable in the Rangeview products, however the change should be kept in mind when comparing across collections. The primary changes for Collection 5 vegetation products are:

• Fine-tuning of the atmospheric correction algorithm and data selection criteria will slightly change the data products.
• The data quality flags (clouds, snow, good quality) were made more useful. (This will stay the same on RangeView).
• The "day of year" of each selected observation during the 16-day composite period is now provided with the imagery (RangeView will display this data layer soon).

Please see the following website for more details:

http://landweb.nascom.nasa.gov/cgi-bin/QA_WWW/newPage.cgi?fileName=MODLAND_C005_changes