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Rennell has been widely known as the father of the modern maps since the publication of his survey works of 1760s. He made the first nearly accurate map of the then Bengal of the Indian Subcontinent entitled “A Bengal Atlas (1779)”, a work which was considered as the most significant geographical contributions of the British Empire for their strategic and administrative interests. The most important feature of the Atlas is the Ganges Basin which flows as the trans-boundary River of South Asia entrenching India, China and Bangladesh. This study reveals the historical and contextual phenomena of the river like old channels, onomastic and old administrative footprints from Rennell’s Atlas around the old courses of Ganges River, more specifically Plate 18 confining within the territorial extent of current Bangladesh Boundary entrapping the history more than 250 years of the aerial extent encompassing 11,651 km². This research also reveals the map accuracy by calculating the modern graticules comparing the former geographic coordinate systems. In order to develop historical dataset based on Rennell’s map, various modern tools of renowned GIS approaches and corresponding attributes like geo-referencing, digitizing, geo-corrections, projection transformation, calculating geometry, pivot table etc. In the 1760s, Rennell was dependent on the primitive sextant instrument and calculated latitude, longitude assuming Fort William of Kolkata as Zero (0) degree. In this research we integrated Bangladesh Transverse Mercator (BTM) considering World Geodetic System 1984 as datum. The results illustrate the volume of rivers, riverine forest, jheel, char land are occupying 116,600; 215,959; 3573; and 15,471 ha respectively in the Rennell’s map which are currently almost disappeared. In the said plate, marsh land covered the maximum area about 118,676 ha while length of Kaccha (unmetalled) road was 1339 km, though recently metalled road length has been increased dramatically. The detected broad administrative unit was 337. The error result in the present research is with 99% accuracy. This research has highlighted the strengths to retrieve underlying evidences and relevant features and statistical/attribute data from the historical maps using remote Sensing (RS) and Geographic Information System (GIS) approaches.

Bangladesh has predominantly four major river systems. Ganges (Padma) River is one of the prominent rivers which support the life and livelihoods of millions of people in Bangladesh. The riverine area of Bangladesh has always faced some changing stages for radical accretion and erosion of lands. Areas of erosion and deposition were determined from successive changes in the bankline positions. Erosion is more active in course line and deposition in sandbar of river. In this research, the area which is eroded and deposited during 1760–2015 (more than 250 years) was analyzed. Erosion and accretion are measured by using Rennell’s map and Landsat MSS, TM and ETM+ satellite imagery with an average duration of 20 years. Processing of image analysis such as layer stack, image enhancement, mosaic and re-projection is done by different tools of image processing software. The Raster and spatial data have been analyzed by image analysis approaches and geo-processing techniques, while quantitative data have been analyzed by using some other statistical computer software program. It was analyzed through the spatial and temporal variation in the study reaches. These are identified by geo-processing techniques of riverbanks. The highest amount of erosional area occurred during 1760–1975 is 38,633 ha, depositional area is 55,140, and therefore, difference is 16,507, with the lowest amount of erosion occurring during 1995–2015. On the other hand, highest amount of deposition occurred during 1760–2015 is 57,605 ha, erosional land is 33,320 ha and there difference is 24,285 ha, with the lowest amount of deposition occurring during 1975–2015. The erosion and deposition has been comparatively low during 1975–1995 and 1995–2015. Finally it is identified that deposition is more active than erosion in Ganges–Padma River in a long period of time (during 1760–2015).