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1.
Murali Krishna Gumma Prasad S. Thenkabail Pardharsadhi Teluguntla Mahesh N. Rao Irshad A. Mohammed Anthony M. Whitbread 《International Journal of Digital Earth》2016,9(10):981-1003
The goal of this study was to map rainfed and irrigated rice-fallow cropland areas across South Asia, using MODIS 250?m time-series data and identify where the farming system may be intensified by the inclusion of a short-season crop during the fallow period. Rice-fallow cropland areas are those areas where rice is grown during the kharif growing season (June–October), followed by a fallow during the rabi season (November–February). These cropland areas are not suitable for growing rabi-season rice due to their high water needs, but are suitable for a short -season (≤3 months), low water-consuming grain legumes such as chickpea (Cicer arietinum L.), black gram, green gram, and lentils. Intensification (double-cropping) in this manner can improve smallholder farmer’s incomes and soil health via rich nitrogen-fixation legume crops as well as address food security challenges of ballooning populations without having to expand croplands. Several grain legumes, primarily chickpea, are increasingly grown across Asia as a source of income for smallholder farmers and at the same time providing rich and cheap source of protein that can improve the nutritional quality of diets in the region. The suitability of rainfed and irrigated rice-fallow croplands for grain legume cultivation across South Asia were defined by these identifiers: (a) rice crop is grown during the primary (kharif) crop growing season or during the north-west monsoon season (June–October); (b) same croplands are left fallow during the second (rabi) season or during the south-east monsoon season (November–February); and (c) ability to support low water-consuming, short-growing season (≤3 months) grain legumes (chickpea, black gram, green gram, and lentils) during rabi season. Existing irrigated or rainfed crops such as rice or wheat that were grown during kharif were not considered suitable for growing during the rabi season, because the moisture/water demand of these crops is too high. The study established cropland classes based on the every 16-day 250?m normalized difference vegetation index (NDVI) time series for one year (June 2010–May 2011) of Moderate Resolution Imaging Spectroradiometer (MODIS) data, using spectral matching techniques (SMTs), and extensive field knowledge. Map accuracy was evaluated based on independent ground survey data as well as compared with available sub-national level statistics. The producers’ and users’ accuracies of the cropland fallow classes were between 75% and 82%. The overall accuracy and the kappa coefficient estimated for rice classes were 82% and 0.79, respectively. The analysis estimated approximately 22.3?Mha of suitable rice-fallow areas in South Asia, with 88.3% in India, 0.5% in Pakistan, 1.1% in Sri Lanka, 8.7% in Bangladesh, 1.4% in Nepal, and 0.02% in Bhutan. Decision-makers can target these areas for sustainable intensification of short-duration grain legumes. 相似文献
2.
Basic principles of mapping for areas of mineral development for reclamation purposes are outlined. In particular special thematic maps should portray both the evolution of man-made landforms subjected to exogenous and endogenous geomorphologic processes and changes in particular elements (components) of those forms resulting from such evolution. More specifically, such indices as elevation, slope, lithology, age, major geomorphological processes, reclamation measures planned or underway, physical-chemical properties, and adjacent land uses are to be incorporated in the legends of maps documenting the existence of mining-altered areas, the severity of the impact, and the prospects for restoration. Translated from: Vestnik Moskovskogo Universiteta, geografiya, 1987, No. 5, pp. 40-46. 相似文献
3.
Estimates of solar radiation distribution in urban areas are often limited by the complexity of urban environments. These limitations arise from spatial structures such as buildings and trees that affect spatial and temporal distributions of solar fluxes over urban surfaces. The traditional solar radiation models implemented in GIS can address this problem only partially. They can be adequately used only for 2‐D surfaces such as terrain and rooftops. However, vertical surfaces, such as facades, require a 3‐D approach. This study presents a new 3‐D solar radiation model for urban areas represented by 3‐D city models. The v.sun module implemented in GRASS GIS is based on the existing solar radiation methodology used in the topographic r.sun model with a new capability to process 3‐D vector data representing complex urban environments. The calculation procedure is based on the combined vector‐voxel approach segmenting the 3‐D vector objects to smaller polygon elements according to a voxel data structure of the volume region. The shadowing effects of surrounding objects are considered using a unique shadowing algorithm. The proposed model has been applied to the sample urban area with results showing strong spatial and temporal variations of solar radiation flows over complex urban surfaces. 相似文献
4.
In recent years, the increase in the number of hurricanes and other costal hazards in the US pose a tremendous threat to the residents of coastal states. According to the National Hurricane Center, Florida is the most vulnerable coastal state to hurricanes. Mitigation policies have been formulated to reduce mortality and provide emergency services by evacuating people from the hazard zone. Many of these evacuees, particularly the elderly or lower income populations, rely on evacuation shelters for temporary housing. Because of the cost and limited use, evacuation shelters are almost exclusively dual use shelters where the primary purpose of the facility is for some other public function (e.g. school, hospital, etc.). In 2000, the estimated shortage of public shelter spaces in Florida was about 1.5 million. The purpose of this study was to rank the existing and candidate shelters (schools, colleges, churches and community centers) available in the state based on their site suitability. The research questions examined in this study include: (1) How many candidate shelters are located in physically suitable areas (e.g. not in a flood prone area, not near hazardous facilities, etc.)?; (2) How many existing shelters are located in physically un suitable areas, but in socially suitable areas (situated in areas with demand)?; (3) How many alternative existing and/or candidate shelters with high/very high physical suitability are located near physically un suitable existing shelters and thus, may be better choices for a shelter?; and (4) How many existing shelters located in physically un suitable areas are not near alternative existing and/or candidate shelters? A Geographic Information System‐based suitability model integrating Weighted Linear Combination (WLC) with a Pass/Fail screening technique was implemented for the 17 counties of Southern Florida. It was found that 48% of the existing shelters are located in physically unsuitable areas. Out of all the candidate shelters, 57% are located in physically unsuitable areas. For 15 of the existing shelters in unsuitable locations, no alternative candidate or existing shelter with medium to high physical suitability exists within 10 miles (16.1 km). 相似文献
5.
A method of analyzing GRACE satellite-to-satellite ranging data is presented which accentuates signals from diurnal ocean
tides and dampens signals from long-period non-tidal phenomena. We form a time series of differences between two independent
monthly mean gravity solutions, one set computed from range-rate data along strictly ascending arcs and the other set computed
from data along descending arcs. The solar and lunisolar diurnal tides having alias periods longer than a few months, such
as K
1, P
1, and S
1, present noticeable variations in the monthly ascending and descending ‘difference’ solutions, while the climate-related
signals are largely cancelled. By computing tidal arguments evaluated along the actual GRACE orbits, we decompose and estimate
residual tidal signals with respect to our adopted prior model GOT4.7. The adjustment in the tidal height is small yet significant,
yielding maximum amplitudes of 4 cm mostly under the Antarctic ice shelves and ~1 cm in general at spatial scales of several
hundred kilometer. Moreover, the results suggest there are possible 1-cm errors in the tide model even over oceans well-covered
by decades of radar altimetry missions. Independent validation of such small adjustments covering wide areas, however, is
difficult, particularly with limited point measurements such as tide gauge. 相似文献
6.
ABSTRACTThis paper provides a study of the changes in land use in urban environments in two cities, Wuhan, China and western Sydney in Australia. Since mixed pixels are a characteristic of medium resolution images such as Landsat, when used for the classification of urban areas, due to changes in urban ground cover within a pixel, Multiple Endmember Spectral Mixture Analysis (MESMA) together with Super-Resolution Mapping (SRM) are employed to derive class fractions to generate classification maps at a higher spatial resolution using an Artificial Neural Network (ANN) predicted Wavelet method. Landsat images over the two cities for a 30-year period, are classified in terms of vegetation, buildings, soil and water. The classifications are then processed using Indifrag software to assess the levels of fragmentation caused by changes in the areas of buildings, vegetation, water and soil over the 30 years. The extents of fragmentation of vegetation, buildings, water and soil for the two cities are compared, while the percentages of vegetation are compared with recommended percentages of green space for urban areas for the benefit of health and well-being of inhabitants. Changes in Ecosystem Service Values (ESVs) resulting from the urbanization have been assessed for Wuhan and Sydney. The UN Sustainable Development Goals (SDG) for urban areas are being assessed by researchers to better understand how to achieve the sustainability of cities. 相似文献
7.
In this study, an empirical model for predicting urban evapotranspiration (ET) is examined for the Phoenix metropolitan area that is in a subtropical desert climate using in situ ET measurements from a local flux tower and remotely sensed moderate-resolution imaging spectroradiometer land products. Annual ET maps of Phoenix are then created for the period from 2001 to 2015 using the empirical model developed. A time-series trend analysis is finally performed using predicted ET maps to discover the spatio-temporal patterns of ET changes during the study period. Results suggest that blue-sky albedo and land surface temperature are two statistically significant variables explanatory to model urban ET for Phoenix. Areas that have experienced significant increases of ET are highly spatially clustered, and are mainly found on the outskirts of the city, while areas of decreasing ET are generally associated with highly developed areas, such as downtown Phoenix. 相似文献
8.
AbstractIn chain and traverse surveys areas are frequently required between chain lines and crooked fences. Commonly these areas are computed from offsets measured at equal intervals, which are so much the shorter according as the sinuosity is the greater. Most frequently Simson's Rules are employed for this computation; for (2m+1) offset ordinates, Simson's First Rule may be used; for (3m+1) ordinates, Simson's Second Rule. The First Rule assumes that the fence is made up of arcs of ordinary parabolae; the Second Rule, of arcs of cubic parabolae. 相似文献
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A national level project on kharif rice identification and acreage estimation is being carried out successfully for several states in the country. A similar
methodology based on the temporal profile for identification and delineation of various land cover classes has been followed
for the Rabi rice acreage estimation. To define rabi rice, rabi season in India starts from November — February to March — June. Though the main growing season is predominantly winter but
the uncertainty of getting cloud free data during the season has resulted in the use of microwave data. A feasibility study
was taken up for early forecasting of the rabi rice area using microwave data. Hierarchical decision rule classification technique was used for the identification of the
different land cover classes. Land preparation, puddling and transplantation were the reasons for the specific backscatter
of rice growing areas. The increase or decrease in the SAR backscatter due to progress in the crop phenology or due to delayed
sowing respectively forms the basis for identifying the rice areas. In addition the potential of optical data of a later date
has been utilized in the form of various indices from bands including MIR to distinctly separate the late sown areas and also
the puddled areas from other areas. This study emphasizes the synergistic use of SAR and optical data for delineating the
rabi rice areas which is of immense use in giving an early forecast. 相似文献
12.
《测量评论》2013,45(14):496-498
AbstractIn the Empire Survey Review for April 1934 (No. 12, pp. 382–4), the Editor has raised the question of the function of the cadastral map. As he remarks, the question is not simple, but it is easier to say what the function of the map is than to decide of what the map should consist in order that it may fulfil its function. Broadly speaking we may state that the function of the map is to record the boundaries of landed property in such a manner as not only to afford a pictorial representation but also to supply data for the identification of these boundaries on the ground when occasion requires. Apart from this the map should show the areas of properties, as this information may be required for taxation purposes. 相似文献
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14.
The aim of the study was to evaluate flash flood potential areas in the Western Cape Province of South Africa, by integrating remote sensing products of high rainfall intensity, antecedent soil moisture and topographic wetness index (TWI). Rainfall has high spatial and temporal variability, thus needs to be quantified at an area in real time from remote sensing techniques unlike from sparsely distributed, point gauge network measurements. Western Cape Province has high spatial variation in topography which results in major differences in received rainfall within areas not far from each other. Although high rainfall was considered as the major cause of flash flood, also other contributing factors such as topography and antecedent soil moisture were considered. Areas of high flash flood potential were found to be associated with high rainfall, antecedent precipitation and TWI. Although TRMM 3B42 was found to have better rainfall intensity accuracy, the product is not available in near real time but rather at a rolling archive of three months; therefore, Multi- sensor precipitation estimate rainfall estimates available in near real time are opted for flash flood events. Advanced Scatterometer (ASCAT) soil moisture observations were found to have a reasonable r value of 0.58 and relatively low MAE of 3.8 when validated with in situ soil moisture measurements. The results of this study underscore the importance of ASCAT and TRMM satellite datasets in mapping areas at risk of flooding. 相似文献
15.
Least-squares collocation may be used for the estimation of spherical harmonic coefficients and their error and error correlations
from GOCE data. Due to the extremely large number of data, this requires the use of the so-called method of Fast Spherical
Collocation (FSC) which requires that data is gridded equidistantly on each parallel and have the same uncorrelated noise
on the parallel. A consequence of this is that error-covariances will be zero except between coefficients of the same signed
order (i.e., the same order and the same coefficient type C–C or S–S). If the data distribution and the characteristics of the data noise are symmetric with respect to the equator, then, within
a given order and coefficient type, the error-covariances amongst coefficients whose degrees are of different parity also
vanish. The deviation from this “ideal” pattern has been studied using data-sets of second order radial derivatives of the
anomalous potential. A total number of points below 17,000 were used having an equi-angular or an equal area distribution
or being associated with points on a realistic GOCE orbit but close to the nodes of a grid. Also the data were considered
having a correlated or an uncorrelated noise and three different signal covariance functions. Grids including data or not
including data in the polar areas were used. Using the functionals associated with the data, error estimates of coefficients
and error-correlations between coefficients were calculated up to a maximal degree and order equal to 90. As expected, for
the data-distributions with no data in the polar areas the error-estimates were found to be larger than when the polar areas
contained data. In all cases it was found that only the error-correlations between coefficients of the same order were significantly
different from zero (up to 88%). Error-correlations were significantly larger when data had been regarded as having non-zero
error-correlations. Also the error-correlations were largest when the covariance function with the largest signal covariance
distance was used. The main finding of this study was that the correlated noise has more pronounced impact on gridded data
than on data distributed on a realistic GOCE orbit. This is useful information for methods using gridded data, such as FSC. 相似文献
16.
Dipak Sarkar S. K. Gangopadhyay A. K. Sahoo 《Journal of the Indian Society of Remote Sensing》2006,34(3):245-260
Visual interpretation of IRS ID LISS-III fused with PAN data (1:12,500 scale) ofPatloinala micro-watershed of Puruliya district, West Bengal was carried out for delineating the physiographic units based on the variations
in image characteristics. The major physiographic units identified were upland(Tanr), medium land(Baid), and low land(Bahal andKanali). The satellite remote sensing data coupled with ground truth were translated in terms of soils using composite interpretation
map as base. The abstraction level attained was phases of soil series based on Soil Taxonomy. On the basis of physiographic
variation and soil or soil site characteristics such as texture, depth, slope, erosion etc. the problem areas were identified
and land use plan has been suggested for the overall development of the micro-watershed. 相似文献
17.
Global Ionosphere Maps of VTEC from GNSS,satellite altimetry,and formosat-3/COSMIC data 总被引：1，自引：1，他引：0
For space geodetic techniques, operating in microwave band, ionosphere is a dispersive medium; thus signals traveling through
this medium are in the first approximation affected proportional to inverse of the square of their frequencies. This effect
allows gaining information about the parameters of the ionosphere in terms of Total Electron Content (TEC) or the electron
density (N
e
). TEC or electron density can then be expressed by means of spherical harmonic base functions to provide a Global Ionosphere
Map (GIM). The classical input data for development of GIMs are obtained from dual-frequency observations carried out at Global
Navigation Satellite Systems (GNSS) stations. However, GNSS stations are in-homogeneously distributed around the world, with
large gaps particularly over the oceans; this fact reduces the precision of the GIM over these areas. On the other hand, dual-frequency
satellite altimetry missions such as Jason-1 provide information about the ionosphere precisely above the oceans; and furthermore
Low Earth Orbiting (LEO) satellites, such as Formosat-3/COSMIC (F/C) provide well-distributed information of ionosphere globally.
This study investigates on global modeling of TEC through combining GNSS and satellite altimetry data with global TEC data
derived from the occultation measurements of the F/C mission. The combined GIMs of vertical TEC (VTEC) show a maximum difference
of 1.3–1.7 TEC units (TECU) with respect to the GNSS-only GIMs in the whole day. The root mean square error (RMS) maps of
combined solution show a reduction of about 0.1 TECU in the whole day. This decrease of RMS can reach up to 0.5 TECU in areas
where no or few GNSS observations are available, but high number of F/C measurement is carried out. This proves that the combined
GIMs provide a more homogeneous global coverage and higher reliability than results of each single method. All comparisons
and validations made within this study provide vital information regarding combination and integration of various observation
techniques in the Global Geodetic Observing System of the International Association of Geodesy. 相似文献
18.
Space images afford a relatively new, rapid, and more economical source of information for the accurate mapping of exogenous factors of relief formation, particularly in areas of highly complex topography. This is illustrated in the mapping of such features along the route of the Baykal-Amur Railroad. Translated by Edward Torrey, Alexandria, VA 22308 from: Geografiya i prirodnyye resursy, 1988, No. 4, pp. 107-112. 相似文献
19.
Gottfried Gerstbach 《Journal of Geodesy》1988,62(4):541-563
The short wavelength geoid undulations, caused by topography, amount to several decimeters in mountainous areas. Up to now
these effects are computed by means of digital terrain models in a grid of 100–500m. However, for many countries these data are not yet available or their collection is too expensive.
This problem can be overcome by considering the special behaviour of the gravity potential along mountain slopes. It is shown
that 90 per cent of the topographic effects are represented by a simple summation formula, based on the average height differences
and distances between valleys and ridges along the geoid profiles,
δN=[30.H.D.+16.(H−H′).D] in mm/km, (error<10%), whereH, H′, D are estimated in a map to the nearest 0.2km. The formula is valid for asymmetric sides of valleys (H, H′) and can easily be corrected for special shapes. It can be used for topographic refinement of low resolution geoids and for
astrogeodetic projects.
The “slope method” was tested in two alpine areas (heights up to 3800m, astrogeodetic deflection points every 170km
2) and resulted in a geoid accuracy of ±3cm. In first order triangulation networks (astro points every 1000km
2) or for gravimetric deflections the accuracy is about 10cm per 30km. Since a map scale of 1∶500.000 is sufficient, the method is suitable for developing countries, too. 相似文献
20.
While there is a large literature on the form of epidemic waves in the time domain, models of their structure and shape in the spatial domain remain poorly developed. This paper concentrates on the changing spatial distribution of an epidemic wave over time and presents a simple method for identifying the leading and trailing edges of the spatial advance and retreat of such waves. Analysis of edge characteristics is used to (a) disaggregate waves into ‘swash’ and ‘backwash’ stages, (b) measure the phase transitions of areas from susceptible, S, through infective, I, to recovered, R, status (S → I → R) as dimensionless integrals and (c) estimate a spatial version of the basic reproduction number, R
0. The methods used are illustrated by application to measles waves in Iceland over a 60-year period from 1915 to 1974. Extensions of the methods for use with more complex waves are possible through modifying the threshold values used to define the start and end points of an event.
相似文献
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