Remote sensing technique often analyzes the thermal characteristics of any area. Our study focuses on estimating land surface temperature (LST) of Raipur City, emphasizing the urban heat island (UHI) and non-UHI inside the city boundary and the relationships of LST with four spectral indices (normalized difference vegetation index, normalized difference water index, normalized difference built-up index, and normalized multiband drought index). Mono-window algorithm is used as LST retrieval method on Landsat 8 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) data, which needs spectral radiance and emissivity of TIRS bands. The entire study is performed on 11 multidate Landsat 8 OLI and TIRS images taken from four different seasons; premonsoon, monsoon, postmonsoon, and winter, in a single-year time period. The Landsat 8 data derived LST is validated significantly with Moderate Resolution Imaging Spectroradiometer (MOD11A1) data. The results show that the UHI zones are mainly developed along the northern and southern portions of the city. The common area of UHI for four different seasons is developed mainly in the northwestern parts of the city, and the value of LST in the common UHI area varies from 26.45°C to 36.51°C. Moreover, the strongest regression between LST and these spectral indices is observed in monsoon and postmonsoon seasons, whereas winter and premonsoon seasons revealed comparatively weak regression. The results also indicate that landscape heterogeneity reduces the reliability of the regression between LST with these spectral indices.
Spatial–temporal distribution of the urban heat islands (UHI) and their changes over Raipur city have been analyzed using multitemporal Landsat satellite data from 1995 to 2016. Land surface temperature (LST) was retrieved through a mono-window algorithm. Some selected land use/land cover (LU–LC) indices were analyzed with LST using linear regression. The urban thermal field variance index (UTFVI) was applied to measure the thermal comfort level of the city. Results show that during the observed period, the study area experienced a gradual increasing rate in mean LST (>1% per annum). The UHI developed especially along the north-western industrial area and south-eastern bare land of the city. A difference in mean LST between UHI and non-UHI for different time periods (2.6°C in 1995, 2.85°C in 2006, 3.42°C in 2009, and 3.63°C in 2016) reflects the continuous warming status of the city. The LST map also shows the existence of a few urban hot spots near the industrial areas, metal roofs, and high density transport parking lots, which are more abundant in the north-western part of the city. The UTFVI map associated with UHI indicates that the inner parts of the city are ecologically more comfortable than the outer peripheries.
Remote sensing images are representations of ground objects as interpreted from space sensors. Image are captured using reflected electromagnetic signal, on the basis of signal intensity identification of objects are achieved. Thus signal values also depends upon sensor capabilities and object characteristics. Sensor which capture remotely sensed images are analyzed on the basis of ground object spectral values. Using images spectral values, ground object characteristic identification are also achieved. In real scenario noise are comprised along with signal which leads to distracts all objects identifications. It also varies across all over the spectral values and on various feature classes. Signal to noise ratio (SNR) describes the quality of a measurement. Higher signal to noise ratio in the image, spectral values of image helps in identification of ground object of presumable quality. SNR computation is prerequisite process before carrying identification analysis on objects. The SNR represents a useful statistics that are computed and compared across different ground features. Hyperion hyperspectral image data set is used to carry study of Signal to Noise ratio. SNR computation is important process, but it is less studied by researches and scientist communities. SNR are computed using three algorithms Homogenous Area, Nearly Homogenous Area and Geostatistical on various feature classes and compared to evaluate its performance on different features. Geostatistical Algorithms is considering large number of spatial pixels, which are heterogeneous never the less results are varies less in comparison to other used algorithms Homogenous Area and Nearly Homogenous area. Feature Barren land have high SNR while comparing with other feature classes using all three used algorithms. Barren land have high signal reflectance and less absorption by atmosphere. The signal to noise ratio is established to be varying across function of both spectral values and ground features.
This study aimed at identifying and mapping hydrothermally altered minerals in parts of Delhi fold belt near Jaipur city, India, using EO-1 Hyperion data. The rock type found in this area is Quartzite of Ajabgarh Series of Delhi Super group. Space based Hyperion hyperspectral data results have been analyzed and compared with different laboratory analysis techniques like X-ray diffraction and spectroradiometer on the selected rock samples. Though, the SNR of the Hyperion image was low (18:1) but different hydrothermally altered and clay minerals like muscovite, kaolinite, kaolinitesmectite and montmorillonite have been identified. The data was in good confirmation with the laboratory and spectroscopic analysis. Surface mineralogy of this area was mapped with the help of Hyperion image and was found in good confirmation with the field observations. On the basis of the mineralogy of the area, it can be concluded that this zone is mainly subjected to the intermediate argillic alteration. During the field survey a fault has also been identified in the study area.
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