From World Wind Wiki
OnEarth Global Mosaic (pseudo)
|Latest release||/ 2007-12-01|
This add-on displays OnEarth Global Mosaic and daily MODIS imagery.
Download: OnEarth.xml or use this installer
(Save a copy of the configuration file in the Config/Earth subdirectory (if not using the installer), and use the Layer Manager to enable layers from this server.)
WMS Global Mosaic is a high resolution global image mosaic of the earth, produced from more than 8200 individual Landsat7 scenes. These images have been collected during 1999-2003. The highest resolution image has a ground relative resolution of 15 meters, or 50 foot. The mosaic contains all nine spectral bands of the Landsat7 ETM+ instrument. Together with the associated Web Map Service Server, the mosaic is known as the WMS Global Mosaic.
- Global Mosaic, pseudocolor (pansharpened 15m/px)
- Global Mosaic, visual
- Global Mosaic base, pseudocolor (30m/px)
- Global Mosaic base, visual
The main difference between Global Mosaic layers is pansharpening. Pansharpening is a generic term describing the use of the higher resolution panchromatic band (15 meters per pixel) to increase the level of detail visible in the lower resolution bands.
Pseudo style is using the Landsat 7 bands 5,4 and 2 to generate the color, and the visual style is using the visual bands 3,2 and 1.
- Daily Planet
A new dataset built for this server, available from Dec 1st 2007 as a beta test. This mosaic is continuosly updated with images from MODIS TERRA, which has almost global daily coverage. This layer is the most current, near-global image of the earth available. The resolution is 250m per pixel in the middle of the swath, less on the edges. New images are added on top of the old data, in the order in which they become available. In general, the newest images are between 6 and 24 hour late, possibly more. The update process is unsupervised, errors might be visible. To produce this mosaic, 80GB per day of raw MODIS scenes are downloaded from the LAADS Web, processed using HDFLook into visual images in a global coordinate system and spliced into the current composite.
- TERRA MODIS
- AQUA MODIS
- TERRA 721 MODIS
- AQUA 721 MODIS
- TERRA NDVI MODIS
- AQUA NDVI MODIS
The two MODIS visual color composites are built daily from high level Near-real-time Subsets produced by the MODIS Rapid Response System. The available subsets are being downloaded and combined in a single composite, at a uniform resolution of 8 arc-second per pixel or about 250m per pixel. In addition to the visual composites above, for both TERRA MODIS and AQUA MODIS, two alternate color mappings are available, the 721 band to RGB mapping and the Normalized Difference Vegetation Index (NDVI).
The 721 mapping is used to identify recently burnt areas, which appear red or brown in this mapping. Since it has increased water contrast compared with the visual images, it can be used to identify flooded areas.
The NDVI is strongly correlated with the density and state of vegetation, and can be used to monitor the state of the crops. These mosaics are updated daily right after the visual composites. More information about the various mapping is available from the Rapid Response System FAQ
There are two operational MODIS instruments, on two satellites named Aqua and Terra. More information about the MODIS instrument and data is available at the MODIS site.