Ocean modellers use bathymetric data sets like ETOPO5 and ETOPO2 to represent the bottom topography. The former data set is based on digitization of depth contours greater than 200 m, and the latter is based on satellite altimetry. Hence, they are not always reliable in shallow regions. An improved shelf bathymetry for the Indian Ocean region (20°E to 112° E and 38°S to 32°N) is derived by digitizing the depth contours and sounding depths less than 200 m from the hydrographic charts published by the National Hydrographic Office, India. The digitized data are then gridded and used to modify the existing ETOPO5 and ETOPO2 data sets for depths less than 200 m. In combining the digitized data with the original ETOPO data set, we apply an appropriate blending technique near the 200 m contour to ensure smooth merging of the data sets. Using the modified ETOPO5, we demonstrate that the original ETOPO5 is indeed inaccurate in depths of less than 200 m and has features that are not actually present on the ocean bottom. Though the present version of ETOPO2 (ETOPO2v2) is a better bathymetry compared to its earlier versions, there still are differences between the ETOPO2v2 and the modified ETOPO2. We assess the improvements of these bathymetric grids with the performance of existing models of tidal circulation and tsunami propagation.
For more details, please refer to: Sindhu et al 2007, J. Earth Syst. Sci.: 116(3); 2007; 261-274. The paper provides a detailed description of the generation, evaluation and validation of the modified bathymetry datasets.
The datasets are provided in three formats : ASCII, NETCDF and BINARY.
NOTE: The tag's value is 0 for depth taken from ETOPO, 1 if the depth is taken from Sindhu's bathemetry dataset and the tag is 0 in her dataset, and 2 if the depth is taken from Sindhu's bathemetry dataset and the tag is 1 in her dataset. The depth values are given in meters.
Please acknowledge National Institute of Oceanography, Goa, India for making the data available. Also please cite the following paper if you use any of the modified datasets.