Land surface emissivity retrieval from airborne sensor over urban areas

In this paper we compare three different methodologies to retrieve land surface emissivity (LSE) over urban areas: the NDVI thresholds method, the temperature and emissivity separation (TES) algorithm and the temperature independent spectral indices (TISI) algorithm. The methodologies were applied to the Airborne Hyperspectral Scanner (AHS) imagery acquired during the Dual-use European Security IR Experiment 2008 (DESIREX 2008) experimental campaign over the city of Madrid (Spain). The images have a spatial resolution of 4 m. The retrieved values are compared to in situ data measured during the campaign at 4 sites. Results show a good performance of the TISI and the TES algorithms over urban surfaces, while the NDVI threshold method does not appear to be capable to distinguish between different artificial surfaces. The land surface temperature (LST) was retrieved with a split window algorithm, using the three different LSE products. Differences of up to 3 K were realized in some surfaces when different LSE maps were used. Over artificial urban surfaces TES and TISI showed better agreement with in-situ data than NDVI. Finally, the TES is the algorithm that best reproduces the LST over an urban area, without the requirement of high temporal resolution of the sensor.