The MODIS Rapid Response System at http://rapidfire.sci.gsfc.nasa.gov/subsets/ supplies geo-registered imagery for about 250 regions of the world.  This imagery, with 250 m spatial resolution and the chance for two looks daily from the Aqua and Terra satellites, provides an outstanding temporal record covering the last two or more years for regions covering about 800x1000 km.

The 4D viewer is part of the Freeware MICRODEM GIS, available from the US Naval Academy. The viewer is designed to supply a simple but powerful interface to perform GIS operations with the MODIS data, supplying a small number of options with reasonable default settings.  Once users gain experience, they can use the full range of GIS options supported by MICRODEM.

MICRODEM can automatically download global topography from the Shuttle Radar Topography Mission (SRTM) to provide the 3D framework for the MODIS imagery, and can get roads, rivers, and political boundaries from the US National Atlas to overlay on the imagery.  This data provides a GIS context to help visualize and locate feature on the MODIS imagery.  The SRTM covers the entire world, but the National Atlas data covers only the United States.  Similar data is generally freely available for the rest of the world in industry standard shape file format, but at this time MICRODEM cannot automatically get it.

MICRODEM contains an embedded Internet Explorer web browser, which can interpret the HTML pages from the MODIS Rapid Response System and get the list of available dates for each region, and automatically download the 250 m imagery and the world files needed to geo-locate the imagery.