Satellite Eye for Galathea 3

Envisat, ESA’s environmental satellite, has taken this radar image while the "Vædderen" was in the port of Tema, Accra in Ghana.

Despite of dense mist that prevails most of the time over the area in that season the ground visibility for radar is always very clear. Since this radar image has been acquired in 2 different polarisations a colour image of the data could be constructed. The mainly greenish colour indicates trees (high vegetation), but where the colour becomes dark trees are sparsely and there is bare the soil (smooth surface). Agriculture fields (low vegetation) are marked as red spots. Pink and white indicates inhabited places. The extension of Accra and its port Tema can be well assessed. In rural areas small villages are also marked in pink. Many ships are waiting at anchor outside the port. Depending on the complexity of their constructions they appear in different colours. The sea is shown just in reddish because backscattering ocean waves do not alter polarisation. The back spots are spilled oil.

Technical information

The data has been recorded while Envisat passed over Africa on the 5th October and was transmitted to the ESA station in Kiruna, Sweden on the next orbit, passing over Europe. The data was available to the Satellite Eye for Galathea 3 project already 3 hours after acquisition.

The radar image has been acquired from ENVISAT ASAR instrument on the 5th October 2006 at 09.49 UTC. The colours of the image are produced using red for the VV polarisation data, green for VH polarisation and blue from the multiplication of both. Pixel size is 79mx79m.

The same pictures in jpg- and in geotif-format to analysis in the picture processing program can be downloaded from:

http://galathea.oersted.dtu.dk/base/dates/2006/10/05/

This week’s picture is delivered by Ørsted, DTU, which is a part of the project Satellite Eye for Galathea 3.