A 32-day Landsat EVI composite image from Google Earth Engine showing San Juan Bautista, California, from April 7 to May 9, 2010. The town is at upper left. The tan-colored areas, upper center, are farm fields. The darker green areas on the bottom are pasture lands and woodland.

Google Earth Engine is offering 8- and 32-day Landsat Enhanced Vegetation Index and Normalized Difference Vegetation Index (NDVI) composites, plus other satellite data, processed and available in a Google Maps type of interface:

http://earthengine.googlelabs.com

Click on Data Catalog, open in workspace. This will open a Google Map window of the earth. Zoom into the area of interest using the + and - bars on navigation tool and then select a date range on the slider in the left hand pane. You may need to wait for the imagery to load. Landsat pixels are 30 meters on a side.

To refer back to the underlying terrain map in order to orient yourself, you can toggle the + or - box on the upper left corner of the EVI imagery box.

The Earth Engine team at Google expects that they will be able to offer longer time periods or user-specified date ranges on some of this data, and an easier interface, later this year, as well as an interface for web developers.

This data can already show some striking contrasts in solar energy flow into the biosphere, and will be a powerful tool for showing and monitoring the effects of large-scale policy, such as USDA commodity subsidies or the Conservation Reserve Program, as well as the effects of management decisions at the 40-acre scale.