Özet:

This study examines the need/importance for ground validation of Landsat 5 Thematic Mapper (TM) and Landsat 7 Enhanced Thematic Mapper Plus (ETM+) observation at 2 gas flaring sites in Rivers State of Niger Delta, Nigeria. 12 Landsat imageries (3 Landsat 5 TM and 9 Landsat 7 ETM+) acquired from 25/03/1987 to 08/03/2013 with < 5 % cloud contamination were used. Both sites are located within a single Landsat scene (Path 188, Row 057). Fieldwork measurements and observations at both sites took place from (04/08/2012-21/09/2012) and (05/08/2019-22/09/2019). The parameters measured are coordinates of points and features, air temperature and relative humidity; and photographs of locations and features were taken. Both air temperature and relative humidity were measured at 3 different levels above the ground surface at 1 minute interval. The closer the distance to the flare stack, the higher the air temperature measured and vice versa. Land Surface Temperature (LST) retrieved from Landsat 5 TM and Landsat 7 ETM+ also shows that the closer the distance to the flare stack, the higher the LST and vice versa. The locational error of points obtained from Landsat 5 TM and Landsat 7 ETM+, and fieldwork measurements give negligible difference of 1.0 × 10-6 to 7.3 × 10-6. Several features, and 4 land use and land cover (LULC) within the sites were clarified. The pattern of plumes from the flare stacks moves outwardly at both sites. Results show that the spatial variability in ground air temperature and derived LST from Landsat 5 TM and Landsat 7 ETM+ differs within 0.8 to 6.0 K because air temperature is different from LST. The results of locational error, LULC, air temperature, LST, and the pattern of plumes observed at both sites show that ground validation through measurement of in-situ data is indispensable to the use of Landsat 5 TM and Landsat 7 ETM+ data and remote sensing technology in the Niger Delta.

Anahtar Kelimeler: