D. Ram Rajak

Space Applications Centre (ISRO) Ahmedabad India · Research Outreach and Training Management Group

Glacier volume estimation is an essential aspect of conducting studies on glacier health. In past decades, various approaches relying on Volume-Area (V-A) scaling or ice thickness distribution have developed. Demonstrative research is attempted for volume estimation of glaciers present in Alaknanda, a Himalayan sub-basin of river Ganga with an area...

Surface energy balance plays a major role in mass balance and glacier melting. In response to climate change, the influence of radiations and turbulent heat fluxes is a governing factor for glacier melting. In the present study, the energy budget method is used to estimate glacier melting at the grid level using ERA-5 data for Gangotri and Saraswat...

Surface roughness is an important parameter in deriving energy balance over the polar ice-sheets and glaciers. In Antarctica, roughness appears as snow patches and is affected by wind transport. It is also influenced by snowfall, snowdrifts, snowmelt, and snow grain size. In this paper, we derive surface roughness using a laser distometer. The roug...

A semi-automated method has been developed for the extraction of land degradation processes using multi sensor data by applying an object-based classification. The object-based approach creates homogenous objects, which is the key component of this classification. The study utilized optical satellite (Landsat-8), microwave (RISAT-1, SAR) and Cartos...

The coastal region of India is highly vulnerable to various threats, including coastal erosion, due to natural processes enhanced by anthropogenic influences. Shoreline change inventories are the prerequisite for identifying the coastal stretches subjected to erosion. In this study, the shoreline of the entire Indian coast was delineated at a scale...

The extent of Arctic sea ice variation has always been of concern for researchers as it directly reacts in response to climatic variation. This article describes the significance of SACTSAT-1 image-based product, Daily Arctic Sea Ice Extent Images (SIE), having 2.25 km resolution and represents the sea ice extent map in the Arctic region. The metho...

Reflectance spectroscopy is a rapid and non-destructive technique for probing the chemical composition of the earth surface. The minerals are characterised by absorption features whose wavelength is function of its crystal chemistry. In the present study, we propose a covariance weighted least square inversion approach to model the wavelength posit...

The extent of Arctic sea ice variation has always been of concern for researchers as it directly reacts in response to climatic variation. This article describes the significance of SACTSAT-1 image-based product, Daily Arctic Sea Ice Extent Images (SIE), having 2.25 km resolution and represents the sea ice extent map in the Arctic region. The metho...

A total of 15 glaciers in the Ny-Ålesund region were studied for their glacier radar zones vis-à-vis ELA over the period 2016–2020, using the multi-seasonal SAR data. All the glaciers were comprised of three zones, namely middle percolation/wet snow, lower percolation/wet snow, and clean ice. Using the anomalies of temperature and precipitation der...

Sea ice has an intense impact on the polar environment, ocean circulation, weather and regional climate. Unexpected melting of sea ice, which is considered as one of the climate change effects, has become a potential threat to the Earth’s climate. The regular monitoring of sea ice and its extent has become very important towards understanding of se...

Sea ice has an intense impact on the polar environment, ocean circulation, weather and regional climate. Unexpected melting of sea ice, which is considered as one of the climate change effects, has become a potential threat to the Earth’s climate. The regular monitoring of sea ice and its extent has become very important towards understanding of se...

Land degradation is an global concern and this atlas presents assessment of land degradation vulnerability in India by geospatial analysis of satellite derived information. (https://vedas.sac.gov.in/static/atlas/dsm/DLD_Atlas_SAC_2021.pdf)

This paper presents a technique of ship route optimization in the Antarctic sea ice region using Dijkstra's algorithm. It studies some of the major parameters that cause resistance to the ship movement through sea ice. It aims to optimize a safe ship route in the Antarctic sea ice between Bharati and Maitri (Indian Research Stations in Antarctica)...

Sea ice is formed when ocean water freezes at a temperature of −1.8 °C. This ice formed over the ocean plays a crucial role in the global climate system. Most of the solar radiation which is incident on sea ice is reflected, and thus, it acts as the earth’s polar refrigerator by limiting the heat absorption. However, it is found over the decades th...

We present the observed area changes in 5234 glaciers (out of which 3435 are debris-free) of Himalaya-Kara-koram (H-K) region, mapped at a scale of 1 : 25,000 using primarily IRS LISS III data between the years 2001 and 2016/2017/2018. Area change is a direct observable parameter in the monitoring of glaciers. The mapping results have been analysed...

Intra and inter-annual variations in the sea ice thickness are highly sensitive indicators of climatic variations undergoing in the earth’s atmosphere and oceans. This paper describes the method of estimating sea ice thickness using radar waveforms data acquired by SARAL/Altika mission during its drifting orbit phase from July 2016 onwards yielding...

Antarctica is the focus of scientific studies considering the largest reservoir of terrestrial water in the form of ice and doubling of ice area during winter due to sea-ice growth. The third pole-Himalaya is equally important due to the large extent of snow and ice cover outside the polar regions, which is a major source of water for the Asian cou...

Polar ecosystem plays a crucial role in global climate change processes. Antarctica is an ideal natural laboratory for advanced research related to climate change and polar ecosystem studies. Concerned global scientific community carries out various scientific experiments by organising expeditions to various research stations located in Antarctica....

A coupled ocean sea ice model is used to carry out sensitivity experiments to decipher the respective roles of wind, heat and freshwater flux forcings in changing the sea ice variability (concentration, volume, salinity, and drift speed) of the Antarctic region with special emphasis near the Indian Stations, Maitri [11.7°E; 70.7°S] and Bharati [76....

An eddy-resolving coupled ocean sea-ice modelling is carried out in the Southern Ocean region (9\(^{\circ }\)–78\(^{\circ }\)E; 51\(^{\circ }\)–71\(^{\circ }\)S) using the MITgcm. The model domain incorporates the Indian Antarctic stations, Maitri (11.7\({^{\circ }}\)E; 70.7\({^{\circ }}\)S) and Bharati (76.1\({^{\circ }}\)E; 69.4\({^{\circ }}\)S)....

Antarctic research station’s existence largely depend on the supply of fuel, food and other commodities through Antarctic Scientific Expedition using ship voyage. Safer Ship Navigation demands high resolution satellite monitoring of the ice conditions which varies from 30 km to 200 km from the Antarctic coast of Research stations. During the last c...

Satellite based remote sensing (RS) data at different spatial and temporal scales can provide crop sown area estimates needed by decision makers. Due to conflict of spatial resolution versus temporal frequency of data collection, getting early and accurate crop sown area at large scale is very difficult. This paper presents a methodology of early e...

Initial signals of climate change is observed at polar regions. Efficient navigation over polar regions is important for Antarctic Expeditions. Optical images tend to be influenced by weather conditions . SAR backscattering characteristics could be affected by the frequency, incident angle and polarization Image fusion algorithm can be applied to o...

A climatic dataset of Sea Ice Occurrence Probability (SIOP) generated for the Antarctic region has been presented. This dataset was used to compare climatic sea ice growth and melt patterns in the eastern and the western Antarctic regions. This sea ice product over the Antarctic region was developed from a long-term (1978-2012) passive microwave da...

A brief description on the potential of earth observation data to derive sea ice parameters needed to provide sea ice advisory for safer shipping has been presented. Extraction of near real time information needed for ship routeing has been discussed with respect to a case study of successful delivery of sea ice condition (derived from satellite da...

To assess the appropriateness of Massachusetts Institute of Technology global ocean circulation model (MITgcm) derived sea ice, monthly average Sea Ice Area (SIA) derived from modelled Sea Ice Concentration (SIC) has been compared with satellite derived SIA (NSIDC/NASATEAM sea ice area) in Arctic region. MITgcm coupled to a thermodynamic sea-ice mo...

An attempt has been made to derive sea ice freeboard from Ka-band Altimeter (SARAL-AltiKa)over Arctic region for the periods 15 March – 15 April, 2013 (spring) and 15 September – 15 October, 2013 (autumn). A waveform template matching technique is employed for classification of leads and floe pixels. The estimated sea ice freeboards were found in c...

Radar altimetry provides an important geophysical parameter, backscatter coefficient (σ0), which is useful in studying target surface characteristics. Ku-band (Oceansat-2 scatterometer- OSCAT) and Ka-band (SARAL-AltiKa altimeter) data are concurrently used to characterize polar surface features over the Antarctic region. Maximum-likelihood classifi...

A new 1 km global IIASA-IFPRI cropland percentage map for the baseline year 2005 has been developed which integrates a number of individual cropland maps at global to regional to national scales. The individual map products include existing global land cover maps such as GlobCover 2005 and MODIS v.5, regional maps such as AFRICOVER and national map...

Wheat is an economically important Rabi crop for the state, which is grown on around 26 % of total available agriculture area in the state. There is a variation in productivity of wheat crop in hilly and tarai region. The agricultural productivity is less in hilly region in comparison of tarai region due to terrace cultivation, traditional system o...

In the present study, quantification of spatial and temporal changes has been carried out between Indian Antarctic Research station Bharati and Amery ice shelf by monitoring the ice margins using RISAT-1 Synthetic Aperture Radar (SAR) data. Spatio-temporal change detection was carried out by comparing the feature's geographic locations from geometr...

This paper highlights the results on spatial pattern of sowing of rapeseed/mustard in four major states in India using multidate Advanced Wide Field Sensor (AWiFS) data for 2010-11 crop season. Geo-referenced, calibrated AWiFS data acquired during October 2010 to February 2011 were used to generate the Normalised Difference Vegetation Index (NDVI)...

A study was conducted to improve precision of crop acreage adopting stratified random sampling approach. Remotely sensed data was used to classify mustard crop for the states of Rajasthan, Madhya Pradesh, Uttar Pradesh, Gujarat and Haryana covering 81% of mustard area of India. A grid of size 5 × 5km was super-imposed on classified image of study a...

Resourcesat-1 satellite offers a unique opportunity of simultaneous observations at three different spatial scales through LISS-IV, LISS-III* (improved LISS-III) and AWiFS sensors from a common platform. The sensors have enhanced capabilities in terms of spectral, spatial and radiometric resolution as compared to earlier Indian Remote sensing Satel...

We developed a procedure for preparing a model for mapping spatially distributed zones of aphid pest (Lipaphis erysimi) outbreaks at a regional level. This study employed near-surface meteorological parameters derived from National Oceanic and Atmospheric Administration (NOAA) Television and Infra-Red Operational Satellites (TIROS) Operational Vert...

The Advanced WiFS sensor of RESOURCESAT- 1 satellite offers significantly improved specifications compared to the WiFS sensor onboard IRS IC, P3 and ID satellites. The improvements are in terms of spatial resolution, radiometry (quantisation levels) and number of spectral bands. In the present study, an attempt has been made to quantify the gains d...

This paper describes the methodology adopted and results obtained during forecasting of national level wheat production in India using multi-date medium resolution Advanced Wide Field Sensor (AWiFS) data. Multidate, geometrically registered and radiometrically normalized Resourcesat-1 AWiFS data were classified using hierarchical decision rules, wh...

This paper describes the methodology adopted and results obtained during forecasting of national level wheat production in India using multi-date medium resolution Advanced Wide Field Sensor (AWiFS) data. Multi-date, geometrically registered and radiometrically normalized Resourcesat-1 AWiFS data were classified using hierarchical decision rules, w...

This paper describes the methodology developed and implemented for Remote Sensing DataBase (RSDB) preparation from multitemporal and multi-sensor data from Indian earth observation satellites. The characteristics of the RSDB prepared over parts of Indo-Gangetic Basin and Central India (IGB&CI) are summarised. An approach for extraction of long term...

1 The first spaceborne hyperspectral sensor, Hyperion, was launched by NASA onboard Earth Observing-I (EO-I). It gathers data in 220 discrete narrow bands along 400-2200 nm spectral range at 30 m spatial resolution in 12 bits radiometry. Each image has 7.5 km swath and 142 km along track coverage. Researchers (Thenkabail et af., 2000, 2002) have sh...

A functional form of crop spectral profile suggested by Badhwar was applied to district-wise wheat Normalised Difference Vegetation Index (NDVI) values relatively normalised by Pseudo-Invariant Feature (urban and built-up) NDVI values, derived from Wide Field Sensor (WiFS) onboard Indian Remote Sensing Satellites (IRS) for 17 dates during 1999–2000...

From the preliminary evaluation of the Resourcesat-1 LISS–III and LISS–IV data it can be inferred that (i) aggregate scene statistics of the two sensors are comparable; (ii) information content of LISS IV red band is higher than that of LISS–III sensor; (iii) the intrinsic dimensionality of LISS–IV data is two whereas that of LISS–III data is three...

Recent work on new approaches and development of yield models for wheat-using space borne remote sensing data in India is discussed. Direct vegetation index (VI)-yield empirical models at farm and district scale explain significant variation in yield. The sensitivity of these models to scene and sensor characteristics and crop discrimination has be...

Cropping pattern is a basic element of cropping system. For the better management of cropping systems, up‐to‐date information on present cropping pattern and changes in cropping pattern is essential. Remote sensing data has shown its great potential in agricultural applications. Wide Field Sensor (WiFS) data available from IRS‐1C, ‐1D and ‐P3 satel...

Dynamic process-based crop simulation models are useful tool in predicting crop growth and yield in response to environmental and cultural factors but are constrained by lack of availability of the required large number of inputs when applied for regional studies. In this study we report (a) development of a prototype Crop Growth Monitoring System...