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using the reservoir close to the power plant of Almaraz, which receives cooling effluents from the plant, as a test area.
ETM+ and TM band 6 imagery were transformed to estimates of ground temperature and then compared. The conversion
is achieved via a straightforward manipulation of the DN values in band 6 of the TM and ETM sensors using the calibra-
tion data supplied by the provider. Transformation of band 6 to surface temperature (EOSAT, 1986) was realized accord-
ing to:
SR = band6- C1 + C2 (1)
K2
T log(K1/SR 4 1) r291s (2)
where:
SR Spectral Radiance (milliwatts per square centimetre per steradian per micrometer)
T Effective at-satellite temperatures in Celsius
Cl Conversion parameter for DN to radiance conversion
C2 Conversion parameter for DN to radiance conversion
Kl1 Calibration constant for offset of detectors in Band 6 of TM and ETM+ sensors
K2 Calibration constant for gain of detectors in Band 6 of TM and ETM- sensors
The estimates of surface temperature may be refined to measurements of absolute surface temperature by using meteoro-
logical data. Atmospheric effects on remotely sensed data can be accounted for by calculating a corrected radiance and
using the black body inversion formula to determine a correct temperature. Meteorological data had been requested for
the study area to correct the results obtained but they have not been made available at the time of analysis. The inability
to calculate absolute surface temperatures determined that the thermal infrared data were compared on the basis of tem-
perature variation over the course of the three data acquisitions. Thus the variability of reservoir surface temperatures
adjacent to the industrial facility was compared with that observed within the Embalse de Valdecañas reservoir located to
the SE of the Almaraz power plant.
3 RESULTS
3.1. Qualitative Analysis
3.1.1 Geology
Comparison of the individual LANDSAT scenes from the TM and ETM+ sensors and the products of image fusion
between panchromatic data and multi-spectral data shows that the lithological boundaries within folded sequences of
Ordovician-Silurian age rocks and those between intrusive rocks and adjacent alluvial deposits are more readily distin-
guished within the multi-spectral data than within the image fusion products.
The fused products created via the image fusion of SPOT Panchromatic data and LANDSAT TM data are unsuitable for
the assessment of textural indicators in areas where significant mis-registration of the data sets occurs. As this mis-regis-
tration coincides with areas of moderate relief characteristic of the intrusive segment of the stratigraphic column, the
image fusion product created by the processing of LANDSAT ETM+ panchromatic and multi-spectral data is superior to
that created from LANDSAT and SPOT data for the purpose of discriminating intrusive rocks. Furthermore the incorpo-
ration of the panchromatic data and the multi-spectral data results in a reduction of the geo-botanical association of
lithologies within the sedimentary sequence.
The LANDSAT ETM+ and SPOT panchromatic data contained evidence of linear features that might be interpreted as
fault lines within the major sedimentary sequences. This identification was enhanced by use of the multi-spectral data
due to the previously mentioned geo-botanical associations. Within the recent alluvial units the correspondence between
fault identification in the geological maps and the imagery was zero. This is partly because many of the faults occur in
areas of agricultural development and partly due to the pixel size of the imagery. Traditionally field mapping in areas
adjacent to river courses identifies fault lines by small displacements within the sequence of alluvial terraces adjacent to
the rivers. Evidently in the case of the rivers studied here these features are too small to be identified within the imagery.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 935