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Digital elevation model (DEM), deriving conventionally from contour data of topographic maps, provides sufficient information regarding the continuously varying topographic surface of the Earth. Though spaceborne DEMs are increasingly being used in earth-environmental-applications, suitability of various freely available spaceborne DEMs [e.g., advanced spaceborne thermal emission and reflection (ASTER), shuttle radar topography mapping mission (SRTM), global multi-resolution terrain elevation data (GMTED)] for topographic and geomorphometric analyzes in tropical regions is yet to be ascertained. In this paper, comparability of these spaceborne DEMs among themselves and also with the DEM (TOPO) prepared from digital contour data of topographic maps is assessed. Results show that various primary and secondary derivatives of ASTER and SRTM DEMs provide relatively better precision and substantial agreement with the corresponding parameters derived from TOPO. Among the spaceborne DEMs, SRTM has relatively higher vertical accuracy (root mean square error = 17.05 m), compared to ASTER (24.09 m) and GMTED (32.85 m). The vertical accuracy of all the spaceborne DEMs strongly depends on the relief and ruggedness of the terrain as well as the type of vegetation. It is proposed that in the absence of other available and acceptable elevation datasets, SRTM and ASTER are equally competent for geomorphometric analysis in tropical regions, while GMTED shows significant loss of terrain information due to coarser spatial resolution.

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Vector borne diseases are a threat to human health. Little attention has been paid to the prevention of these diseases. We attempted to identify the significant wetland characteristics associated with the spread of chikungunya, dengue fever and malaria in Kerala, a tropical region of South West India using multivariate analyses (hierarchical cluster analysis, factor analysis and multiple regression). High/medium turbid coastal lagoons and inland water-logged wetlands with aquatic vegetation have significant effect on the incidence of chikungunya while dengue influenced by high turbid coastal beaches and malaria by medium turbid coastal beaches. The high turbidity in water is due to the urban waste discharge namely sewage, sullage and garbage from the densely populated cities and towns. The large extent of wetland is low land area favours the occurrence of vector borne diseases. Hence the provision of pollution control measures at source including soil erosion control measures is vital. The identification of vulnerable zones favouring the vector borne diseases will help the authorities to control pollution especially from urban areas and prevent these vector borne diseases. Future research should cover land use cover changes, climatic factors, seasonal variations in weather and pollution factors favouring the occurrence of vector borne diseases.

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Geospatial tools play significant role in forest ecology and management, where vegetation indices and transformations have been extensively used for vegetation characterization. Hence, in this study, an attempt has been made to characterize the various hydrologic regimes in Wayanad Wildlife Sanctuary, Wayanad district, Kerala using geospatial tools. The study area was focused on Muthanga , a part of the Wayanad Wildlife Sanctuary of Wayanad district, Kerala with an area of 87.13 km 2 , where the major vegetation types are moist deciduous with a few scattered patches of evergreen and forests plantation. Out of the many spectral indices employed in the hydrologic studies of the forest areas, tasseled cap wetness index, Normalised Difference Vegetation Index (NDVI) and Normalised Difference Water Index NDWI were used in this study. Since topography also affects the hydrological processes by controlling the spatial distribution of soil moisture in a realistic way, some of the terrain indices, e.g., topographic wetness index (TWI) were also employed in the present study. Statistical analysis was conducted in order to unravel the Original Research Article

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