Surface temperature measurement from space : a case study in the South Western Cape of South Africa
CITATION: Sandham, L. A. & Zietsman, H. L. 1997. Surface temperature measurement from space : a case study in the South Western Cape of South Africa. South African Journal of Enology & Viticulture, 18(2):25-30, doi:10.21548/18-2-2250.
The original publication is available at http://www.journals.ac.za/index.php/sajev
This paper reports on the use of Landsat Thematic Mapper (TM) thermal infrared (TIR) and Transformed Normalised Difference Vegetation Index (TNDVI) data to map summer surface temperature distribution in a portion of the South Western Cape (South Africa). It adopts a ground truth calibration approach, as a possible solution for alleviating the paucity of spatial temperature data. Means and standard deviations of the TIR and transformed NDVI of all pixels within a radius of 120 m around each ground truth point were regressed on spatially collocated surface-observed temperature data. Linear multiple regression analysis showed that mean TIR and standard deviation of TNDVI were effective in accounting for 43 % of variation in surface temperature. The regression equation was used to generate a temperature map at a spatial resolution of 30 m, showing good agreement with expected mesoscale spatial temperature patterns in terms of general climatic principles. The temperature map provides a useful tool for depicting and assessing the spatial variation in daily temperatures, providing information currently unavailable to the fruit-producing farmers in the South Western Cape.