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1.
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 × 5 km was super-imposed on classified image of study area and proportion of
mustard crop within the grid was ascertained. Crop proportion was used to determine strata. Stratification was done based
on equal interval of proportion, equal sample number and cumulative square root of frequency method. Cumulative square root
of frequency method gave highest precision in all the cases. 相似文献
2.
Sheshakumar K. Goroshi R. P. Singh S. Panigrahy J. S. Parihar 《Journal of the Indian Society of Remote Sensing》2011,39(3):315-321
This paper highlights the spatial and temporal variability of atmospheric columnar methane (CH4) concentration over India and its correlation with the terrestrial vegetation dynamics. SCanning IMaging Absorption spectrometer
for Atmospheric CHartographY (SCIAMACHY) on board ENVIronmental SATellite (ENVISAT) data product (0.5° × 0.5°) was used to
analyze the atmospheric CH4 concentration. Satellite Pour l'Observation de la Terre (SPOT)-VEGETATION sensor’s Normalized Difference Vegetation Index
(NDVI) product, aggregated at 0.5° × 0.5° grid level for the same period (2004 and 2005), was used to correlate the with CH4 concentration. Analysis showed mean monthly CH4 concentration during the Kharif season varied from 1,704 parts per billion volume (ppbv) to 1,780 ppbv with the lowest value in May and the highest value
in September. Correspondingly, mean NDVI varied from 0.28 (May) to 0.53 (September). Analysis of correlation between CH4 concentration and NDVI values over India showed positive correlation (r = 0.76; n = 6) in Kharif season. Further analysis using land cover information showed characteristic low correlation in natural vegetation region
and high correlation in agricultural area. Grids, particularly falling in the Indo-Gangetic Plains showed positive correlation.
This could be attributed to the rice crop which is grown as a predominant crop during this period. The CH4 concentration pattern matched well with growth pattern of rice with the highest concentration coinciding with the peak growth
period of crop in the September. Characteristically low correlation was observed (r = 0.1; n = 6) in deserts of Rajasthan and forested Himalayan ecosystem. Thus, the paper emphasizes the synergistic use of different
satellite based data in understanding the variability of atmospheric CH4 concentration in relation to vegetation. 相似文献
3.
A detailed gravimetric geoid in the North Atlantic Ocean, named DGGNA-77, has been computed, based on a satellite and gravimetry
derived earth potential model (consisting in spherical harmonic coefficients up to degree and order 30) and mean free air
surface gravity anomalies (35180 1°×1° mean values and 245000 4′×4′ mean values). The long wavelength undulations were computed
from the spherical harmonics of the reference potential model and the details were obtained by integrating the residual gravity
anomalies through the Stokes formula: from 0 to 5° with the 4′×4′ data, and from 5° to 20° with the 1°×1° data. For computer
time reasons the final grid was computed with half a degree spacing only. This grid extends from the Gulf of Mexico to the
European and African coasts.
Comparisons have been made with Geos 3 altimetry derived geoid heights and with the 5′×5′ gravimetric geoid derived byMarsh andChang [8] in the northwestern part of the Atlantic Ocean, which show a good agreement in most places apart from some tilts which
porbably come from the satellite orbit recovery. 相似文献
4.
An inverse Poisson integral technique has been used to determine a gravity field on the geoid which, when continued by analytic
free space methods to the topographic surface, agrees with the observed field. The computation is performed in three stages,
each stage refining the previous solution using data at progressively increasing resolution (1o×1o, 5′×5′, 5/8′×5/8′) from a decreasing area of integration. Reduction corrections are computed at 5/8′×5/8′ granularity by
differencing the geoidal and surface values, smoothed by low-pass filtering and sub-sampled at 5′ intervals. This paper discusses
1o×1o averages of the reduction corrections thus obtained for 172 1o×1o squares in western North America.
The 1o×1o mean reduction corrections are predominantly positive, varying from −3 to +15mgal, with values in excess of 5mgal for 26 squares. Their mean andrms values are +2.4 and 3.6mgal respectively and they correlate well with the mean terrain corrections as predicted byPellinen in 1962. The mean andrms contributions from the three stages of computation are: 1o×1o stage +0.15 and 0.7mgal; 5′×5′ stage +1.0 and 1.6mgal; and 5/8′×5/8′ stage +1.3 and 1.8mgal. These results reflect a tendency for the contributions to become larger and more systematically positive as the wavelengths
involved become shorter. The results are discussed in terms of two mechanisms; the first is a tendency for the absolute values
of both positive and negative anomalies to become larger when continued downwards and, the second, a non-linear rectification,
due to the correlation between gravity anomaly and topographic height, which results in the values continued to a level surface
being systematically more positive than those on the topography. 相似文献
5.
A new gravity map, a new marine geoid around Japan and the detection of the Kuroshio current 总被引:3,自引:0,他引:3
About half a million marine gravity measurements over a 30∘×30∘ area centered on Japan have been processed and adjusted to produce a new free-air gravity map from a 5′×5′ grid. This map
seems to have a better resolution than those previously published as measured by its correlation with bathymetry. The grid
was used together with a high-degree and -order spherical harmonics geopotential model to compute a detailed geoid with two
methods: Stokes integral and collocation. Comparisons with other available geoidal surfaces derived either from gravity or
from satellite altimetry were made especially to test the ability of this new geoid at showing the sea surface topography
as mapped by the Topex/Poseidon satellite. Over 2 months (6 cycles) the dynamic topography at ascending passes in the region
(23∘47∘N and 123∘147∘E) was mapped to study the variability of the Kuroshio current.
Received: 15 July 1994 / Accepted: 17 February 1997 相似文献
6.
G Ja Sankar M Jagannadha Rao B S Prakasa Rao D K Jugran 《Journal of the Indian Society of Remote Sensing》2001,29(3):165-174
Hydromorphogeological studies have been carried out around Agnigundala mineralised belt (longitude 70°.39′ - 16°.51′ and latitude 16°.2′ - 16°.15′) using remote sensing IRS-IB and SPOT data for ground water exploration. Based on erosional and depositional characters of various geomorphic units like Hills (Structural and denudational) Pediment, Buried pediment, plains and valley fills have been identified in various lithologies like granite, granite gneiss, biotite schist, phyllite,. quartzite and dolomite. The acclamations of individual geomorphic units through visual interpretation are verified from field data. The groundwater potentials of the individual geomorphologic units have been evaluated to obtain a complete hvdrogcological picture of the area. The field data have further helped in quanlifying various geomorphological units with reference to their potential for ground water occurrence. 相似文献
7.
R. H. Rapp 《Journal of Geodesy》1967,41(1):55-65
In support of requirements for the U.S. Air Force Cambridge Research Laboratories, gravity anomalies have been upward continued
to several elevations in different areas of the United States. One area was 340 to 400 N in latitude and 960 to 1030 W in longitude, generally called the Oklahoma area. The computations proceeded from 26, 032 point anomalies to the prediction
of mean anomalies in 14, 704, 2.5′×2.5′ blocks and 9,284, 5′×5′ blocks. These anomalies were upward continued along 28 profiles
at 5′ intervals for every 30′ in latitude and longitude. These anomalies at elevations were meaned in various patterns to
form mean 30′×30″, 10×10, 50×50 blocks. Comparisons were then made to the corresponding ground values. The results of these comparisons lead to practical
recommendations on the arrangement of flight profiles in airborne gravimetry. 相似文献
8.
The purpose of this study is to develop probabilistic seismic hazard maps for Yangon and its surrounding areas including ‘Peak
Ground Acceleration’ values for 2% and 10 % probability of the exceedance in 50 years at rock sites. The present study area
is situated between the latitudes of N 13°37′ and N 20°2′ and the longitudes of E 93°35′ and E 99°5′. The study areas are
focused on nine source zones centered around Yangon with the radius of about 200 km. The probabilistic seismic hazard maps
are created by ArcGIS-9.3 software. 相似文献
9.
R. K. Somashekar P. Ravikumar S. V. Sowmya Mubhashir Aziz Dar A. S. Ravikumar 《Journal of the Indian Society of Remote Sensing》2011,39(1):95-106
The study area, Hesaraghatta watershed is located between 77° 20′ to 77° 42′ E longitude and 13° 10′ to 13° 24′ N latitude
with an area of 600.01 km2. Thematic layers such as Land Use/Land Cover, drainage, soil and hydrological soil group were generated from IRS–1D LISS
III satellite data (FCC). An attempt was made to estimate runoff using Soil Conservation Service (SCS) curve number model
and it was estimated to be 1960, 2066, 1870 and 1810 mm for sub-watersheds 1, 2, 3 and 4 respectively. Quantitative morphometric
analysis was carried out for the entire watershed and the four sub-watersheds independently by estimating their (a) linear
aspects like stream order, stream length, stream length ratio, bifurcation ratio, length of overland flow, drainage pattern
(b) aerial aspects like shape factor, circulatory ratio, elongation ratio and drainage density and (c) relief aspects like
basin relief, relief ratio, relative relief and ruggedness number. Drainage density was estimated to be 1.23 km/km2 designating the study area as a very coarse textured watershed. 相似文献
10.
C. S. Reddy 《Journal of the Indian Society of Remote Sensing》2010,38(3):577-584
India is one of the 12 mega biodiversity countries in the world. There are still many areas where inadequate information on
plant wealth is available. Gap area prioritization is of utmost concern to understand the species richness of different parts
of India. In this context survey-gap analysis was carried out to assess exploration status and to prioritise areas using integrated
approach through taxonomical data and geoinformatics. In order to highlight the gaps in botanical exploration in the country,
the present case study was conducted in Adilabad district of Andhra Pradesh. A grid size of 5′×5′ has been prepared to analyse
the exploration status. The results indicated that most parts of study area have been under-explored and unexplored. Of the
200 grids, only one grid has been well explored with species collections of above 100. The study brought to light that moist
deciduous forests were not covered during floristic studies. Comparative analysis with disturbance index and biological richness
maps evidently points out that explorations were undertaken only in high disturbed zones and areas of low to medium biological
richness. This geospatial analysis clearly points the need for more attention to the exploration of tropical forests in India.
There is a need of systematic botanical studies to prioritise the conservation strategies of varied natural ecosystems. It
is recommended for national level survey-gap analysis as an important step to determine the floristic wealth, species representativeness
and distribution. 相似文献
11.
The passive satellite GFZ-1 has been orbiting the Earth since April 1995. The purpose of this mission is to improve the current
knowledge of the Earth's gravity field by analysing gravitational orbit perturbations observed at unique low altitudes, below
400 km. GFZ-1 is one target of the international satellite laser ranging ground network. An evaluation of the first 30 months
of GFZ-1 laser tracking data led to a new version of the global GRIM4-S4 satellite-only gravity field model: GRIM4-S4G. Information
was obtained from GFZ-1 data for spherical harmonic coefficients up to degree 100, which was not possible in any earlier satellite-only
gravity field solution. GFZ-1's contribution to a global 5 × 5° geoid and gravity field representations is moderate but visible
with a 1 cm and 0.1 mGal gain in accuracy on a level of 75 cm and 5 mGal, respectively.
Received: 10 November 1998 / Accepted: 19 April 1999 相似文献
12.
The New Hebrides experiment consisted of setting up a pair of DORIS beacons in remote tropical islands in the southwestern
Pacific, between 1993 and 1997. Because of orbitography requirements on TOPEX/Poséidon, the beacons were only transmitting
to SPOT satellites. Root-mean-square (RMS) scatters at the centimeter level on the latitude and vertical components were achieved,
but 2-cm RMS scatters affected the longitude component. Nevertheless, results of relative velocity (123 mm/year N250°) are
very consistent with those obtained using the global positioning system (GPS) (126 mm/yr N246°). The co-seismic step (12 mm
N60°) related to the Walpole event (M
W = 7.7) is consistent with that derived from GPS (10 mm N30°) or from the centroid moment tensor (CMT) of the quake (12 mm
N000°).
Received: 19 November 1999 / Accepted: 17 May 2000 相似文献
13.
On the basis of gravity field model (EIGEN_CG01C), together with multi-altimeter data, the improved deflection of the vertical gridded in 2'×2' in China marginal sea and gridded in 5'×5' in the global sea was determined by using the weighted method of along-track least squares, and the accuracy is better than 1.2^# in China marginal sea. As for the quality of the deflection of the vertical, it meets the challenge for the gravity field of high resolution and accuracy, it shows that, compared with the shipboard gravimetry in the sea, the accuracy of the gravity anomalies computed with the marine deflection of the vertical by inverse Vening-Meinesz formula is 7.75 m.s ^-2. 相似文献
14.
Least-squares prediction using an empirically deduced local covariance function was performed to investigate the temporal
change in the rates of vertical crustal movements in the Tohoku district, Japan. Levelling data covering an area of approximately
450 × 275 km2 observed between 1966 and 1995 were used and the results shown in the form of contour maps. Firstly we derived a covariance
function of the rates of vertical crustal movement with a Gaussian form function. We used this function to estimate the spatial
distribution of the rates of vertical crustal movements. By the present method, a steady tilt of the Tohoku district to the
east, toward the Japan Trench and an areal uplift in the southwestern part were well reproduced. Moreover, a significant temporal
change in vertical movement rates is clearly seen.
Received: 15 July 1996 相似文献
15.
A synthetic Earth for use in geodesy 总被引:1,自引:0,他引:1
R. Haagmans 《Journal of Geodesy》2000,74(7-8):503-511
A synthetic Earth and its gravity field that can be represented at different resolutions for testing and comparing existing
and new methods used for global gravity-field determination are created. Both the boundary and boundary values of the gravity
potential can be generated. The approach chosen also allows observables to be generated at aircraft flight height or at satellite
altitude. The generation of the synthetic Earth shape (SES) and gravity-field quantities is based upon spherical harmonic
expansions of the isostatically compensated equivalent rock topography and the EGM96 global geopotential model. Spherical
harmonic models are developed for both the synthetic Earth topography (SET) and the synthetic Earth potential (SEP) up to
degree and order 2160 corresponding to a 5′×5′ resolution. Various sets of SET, SES and SEP with boundary geometry and boundary
values at different resolutions can be generated using low-pass filters applied to the expansions. The representation is achieved
in point sets based upon refined triangulation of a octahedral geometry projected onto the chosen reference ellipsoid. The
filter cut-offs relate to the sampling pattern in order to avoid aliasing effects. Examples of the SET and its gravity field
are shown for a resolution with a Nyquist sampling rate of 8.27 degrees.
Received: 6 August 1999 / Accepted: 26 April 2000 相似文献
16.
In the present study analysis of Landsat MSS, TM and SPOT imagery and digital analysis of IRS LISS-1 data of Doon Valley was carried out. Various geomorphic features were identified and classified, morphostratigraphy of the area has been established. Main geomorphic units of the area are Mussoorie Hill Range (Denudational), Siwalik Hills (Structural), Remnant Hills (Residual). Siwalik Piedmont. Doon Piedmont, River Terraces and Flood Plain. Three large fan lobes are identified on Doon Piedmont deposits, viz., Western fan lobe, Central fan lobe and Eastern fan lobe. Average slope of these three fan lobes are 2°21′, 2°3′, and 1°24′ for the western, central and eastern fan lobes respectively. Western and central fan lobes have been affected by neotectonic activity which is reflected in transverse profiles. 相似文献
17.
Isaac Dadzie 《地球空间信息科学学报》2007,10(1):27-32
A new computational procedure for derivation of marine geoid on a 2.5′×2.5′grid in a non-tidal system over the South China Sea and the Philippine Sea from multi-satellite altimeter sea surface heights is discussed. Single-and dual-satellite crossovers were performed, and components of deflections of the vertical were determined at the crossover positions using Sand-well's computational theory, and gridded onto a 2.5′×2.5′resolution grid by employing the Shepard's interpolation procedure. 2.5′×2.5′grid of EGM96-derived components of deflections of the vertical and geoid heights were then used as reference global geopotential model quantities in a remove-restore procedure to implement the Molodensky-like formula via 1D-FFT technique to predict the geoid heights over the South China Sea and the Philippine Sea from the gridded altimeter-derived components of deflec-tions of the vertical. Statistical comparisons between the altimeter-and the EGM96- derived geoid heights showed that there was a root-mean-square agreement of ±0.35 m between them in a region of less tectonically active geological structures. However, over areas of tectonically active structures such as the Philippine trench, differences of about -19.9 m were obtained. 相似文献
18.
This research deals with some theoretical and numerical problems of the downward continuation of mean Helmert gravity disturbances.
We prove that the downward continuation of the disturbing potential is much smoother, as well as two orders of magnitude smaller
than that of the gravity anomaly, and we give the expression in spectral form for calculating the disturbing potential term.
Numerical results show that for calculating truncation errors the first 180∘ of a global potential model suffice. We also discuss the theoretical convergence problem of the iterative scheme. We prove
that the 5′×5′ mean iterative scheme is convergent and the convergence speed depends on the topographic height; for Canada, to achieve an
accuracy of 0.01 mGal, at most 80 iterations are needed. The comparison of the “mean” and “point” schemes shows that the mean
scheme should give a more reasonable and reliable solution, while the point scheme brings a large error to the solution.
Received: 19 August 1996 / Accepted: 4 February 1998 相似文献
19.
Land-use change and Land-cover classes in Garur Ganga watershed of Bageshwar district in Uttranchal State during the periods 1963–1996 and 1986–1996 were analyzed through Survey of India Topographical Sheet and visual interpretation of LANDSAT 5 TM image bands 2, 3 and 4 using Geographical Information System (GIS). The detailed analysis have revealed that the area under agriculture and settlement increased from 34.98 to 42.34%. whereas the forest and barren land show a declining trend. Expansion of agriculture land and builtup areas have been found to be maximum in the 1200–1600 m elevation zone with 7–14° slope class. The loss of vegetation cover has been estimated to be 5.07% between 1963-1996 and 0.81% between 1986–1996. 相似文献
20.
Bimal Kumar Bhattacharya Keshav R. Gunjal Sushma Panigrahy Jai Singh Parihar 《Journal of the Indian Society of Remote Sensing》2011,39(3):393-406
Albedo determines radiation balance of land (soil-canopy complex) surface and influence boundary layer structure of the atmosphere.
Accurate surface albedo determination is important for weather forecasting, climate projection and ecosystem modelling. Albedo-rainfall
feedback relationship has not been studied so far using observations on spatial scale over Indian monsoon region due to lack
of consistent, systematic and simultaneous long-term measurements of both. The present study used dekadal (ten-day) composite
of satellite (e.g. NOAA) based Pathfinder AVHRR Land (PAL) datasets between 1981 and 2000 over India (68–100°E, 5–40°N) at
8 km spatial resolution. Land surface albedo was computed using linear transformation of red and near infrared (NIR) surface
reflectances. The cloud effects were removed using a smoothening filter with harmonic analysis applied to time series data
in each year. The monthly, annual and long term means were computed from dekadal reconstructed albedo. The mean per year and
coefficient of variation (CV) of surface albedo over seventeen years, averaged over Indian land region, were found to show
a significantly decreasing (0.15 to 0.14 and 60 to 40%, respectively) trend between 1981 and 2000. Among all the land use
patterns, the inter-annual variation of albedo of Himalayan snow cover showed a significant and the steepest reducing trend
(0.42 – 0.35) followed by open shurbland, grassland and cropland. No significant change was noticed over different forest
types.. This could be due to increase in snow melting period and snow melt area. A strong inverse exponential relation (correlation
coefficient r = 0.95, n = 100) was found between annual rainfall and annual albedo over seven rainfall zones. The decreasing trend in snow-albedo
of accumulation period (September to March) follows the declining trend in measured south-west monsoon rainfall between 1988
(980 mm) to 1998 (880 mm) over India. This finding perhaps suggests the possible reversal of reported coupling of increased
snowfall followed by lower monsoon rainfall. 相似文献