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Posts tagged Nasa

Traces of Humankind – South Africa

30.2S 24.6E

July 3rd, 2013 Category: Earth Observation, Snapshots VIIRS/MODISSuomi-NPP/Aqua

South Africa – July 1st, 2013

VIIRS – Night Visible Image

MODIS – True-Color Image

Satellite images are an incredible tool to assess the health status of the Earth.

However, while macro-effects of human activities are clearly evident (i.e. deforestation, oil spill, etc.), the real impact of mankind on our Planet was not always easy to identify from Space.

Sometimes it is possible to understand how a region is changing just by combining data from different satellite instruments. Paradoxically, sometimes you just simply turn off the light to notice details not otherwise visible.

The main image represents the combination of the Night band of the VIIRS instrument (on-board the NASA’s Suomi-NPP satellite) with the True-Color band combination of the MODIS instrument (on-board the NASA’s Aqua satellite).

The extent of urban areas captured by the Night Image is clearly visible using the True-Color Image as a background. Small agricultural fires are visible as small groups of white dots close to the major villages (in the middle right part of the image).

The city of Cape Town is visible in the lower left part of the image, while the municipalities of Johannesburg, Pretoria, Vereeniging, Brits and Rustenburg (in the upper right part of the image) show that the extent of the towns has become a single (giant) urban area.

In the small boxes at the beginning, the two images used for the combination.

ASAR Image Orthorectification

April 3rd, 2009 Category: Earth Observation

Figure 1 - 3D Model

Figure 1 - 3D Model

These images of Reunion Island provide a clear example of the improvements made through the use of the orthorectification technique.
The original product has been processed, orthorectified and projected using the Chelys SRRS (Satellite Rapid Response System). The orthorectification process is now fully automatic and transparent. The Digital Elevation Model used is the Nasa SRTM v4 (Shuttle Radar Topography Mission).

The proper DEM is selected according to the image resolution: from 15 arcseconds up to 1 arcsecond (only available for USA). The performance of the system are kept in real-time. The entire correction process takes less than 20 seconds per product.

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