Satellite Imaging

Ikonos Satellite Imaging
Thermal Satellite Imaging
Differential Radar Interferometry (DInSAR)

Thermal Satellite Imaging

Landsat 7 satellite thermal images can be used as a volcano-monitoring tool, as a large-scale overview with a thermal resolution of ±10°C. The spatial terrain resolution is approximately 60 m, after reduction of atmospheric and terrain (altitude and small-scale surface temperature) interferences.

The Nisyros volcano has been monitored from space in the period 2000-2002 using:

• Surface temperature (T) maps extracted from Landsat 7 ETM+ data (60 m resolution - 1 band) every 16 days (Figs. 20 and 21)
• Surface temperature maps extracted from the ASTER radiometer (90 m resolution - 5 bands).

Two field campaigns were conducted, one in September 2000 and the other in October 2000. The campaigns aimed at collecting “ground truth” temperature data, twice a day, to calibrate the surface temperatures computed from channel 6 of the satellite Landsat 7.

The land surface data were collected inside Stefanos Crater, and at the two geothermal wells nearby. Additional data collection included the sea surface temperatures and local meteorological data (air temperature, humidity, pressure) from the GEOWARN meteorological station situated in between the ground truth points.

Night-time imagery was chosen in order to a) remove the topographic signal evident in the 1997 Landsat 5 scene and b) maximize the temperature difference between the Stefanos Crater and the surroundings, thus avoiding release of stored heat from daytime insolation .

Fig. 20 The orthorectified and atmospheric corrected low gain thermal band 6-1 of Landsat 7, ETM+ Image of Nisyros Island. The "1976 US Standard Atmospheric Model" has been used in ATCOR 3 software package to perform the atmospheric correction. The temperature ranges from 12 to 28 °C. National Kapodistrian University of Athens (NKUA)
(Click on image to enlarge).

Fig. 21 Temperature map of the craters region in Nisyros. A thermal anomaly indicated by red pixels inside Stephanos Crater can be observed. Landsat 7 ETM, low gain, 20.10.2002, 20.28 GMT. National Kapodistrian University of Athens (NKUA)
(Click on image to enlarge).

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