共查询到20条相似文献，搜索用时 781 毫秒
2.
The “blooming desert”, or the explosive development and flowering of ephemeral herbaceous and some woody desert species during years with abnormally high accumulated rainfall, is a spectacular biological phenomenon of the hyper-arid Atacama Desert (northern Chile) attracting botanists, ecologists, geo-scientists, and the general public from all over the world. However, the number of “blooming deserts”, their geographical distribution and spatio-temporal patterns have not been quantitatively assessed to date. Here, we used NDVI data from the Global Inventory Modeling and Mapping Studies (GIMMS) project to reconstruct the annual land surface phenology (LSP) of the Atacama Desert using a non-parametric statistical approach. From the reconstructed LSP, we detected the “blooming deserts” as positive NDVI anomalies and assessed three dimensions of the events: their temporal extent, intensity of “greening” and spatial extent. We identified 13 “blooming deserts” between 1981 and 2015, of which three (1997–98, 2002–03, and 2011) can be considered major events according to these metrics. The main event occurred in 2011, spanning 180 days between July and December 2011, and spread over 11,136 km2 of Atacama dry plains. “Blooming deserts” in Atacama have been triggered by the accumulation of precipitation during a period of 2 to 12 months before and during the events. The proposed three-dimensional approach allowed us to characterize different types of “blooming deserts”: with longer episodes or larger spatial distribution or with different “greening” intensities. Its flexibility to reconstruct different LSP and detect anomalies makes this method a useful tool to study these rare phenomena in other deserts in the world also. 相似文献
3.
none 《The Cartographic journal》2013,50(2):155-175
AbstractThe organization lineage of the UK Defence Geographic and Imagery Intelligence Agency can be traced back to the seventeenth century. For much of this time the organization, bearing a succession of different titles, formed only a very small section of the armed forces, and, until the World War of 1914–1918, its main duties were the creation and maintenance of a map collection and the acquisition of geographical data of foreign countries. The survey and mapping innovations made during the war greatly enlarged the remit of what was now termed the Geographical Section General Staff (MI4). This paper outlines the work of MI4 in the inter-war years taking account of the principal personalities involved, and traces the controversial background to the creation in 1943 of the Directorate of Military Survey — the immediate predecessor of the DGIA. 相似文献
4.
《地理信息系统科学与遥感》2013,50(4):498-513
The objective of the present study, developed in a mountainous region in Brazil where many landslides occur, is to present a method for detecting landslide scars that couples image processing techniques with spatial analysis tools. An IKONOS image was initially segmented, and then classified through a Batthacharrya classifier, with an acceptance limit of 99%, resulting in 216 polygons identified with a spectral response similar to landslide scars. After making use of some spatial analysis tools that took into account a susceptibility map, a map of local drainage channels and highways, and the maximum expected size of scars in the study area, some features misinterpreted as scars were excluded. The 43 resulting features were then compared with visually interpreted landslide scars and field observations. The proposed method can be reproduced and enhanced by adding filtering criteria and was able to find new scars on the image, with a final error rate of 2.3%. 相似文献
5.
We consider disturbances of total electron content (TEC) of the high-latitude ionosphere provided by the GPS global navigation satellite system before and during the magnetic storm on April 5, 2010. Simultaneously, we examine magnetic data from all available magnetometer arrays in the northern hemisphere, augmented with data from scanning photometers and riometers. The substorm onset, during both non-storm and storm periods, is found to cause significant enhancement of TEC scintillations characterized by the TEC time derivative dTEC. Comparison of 2D maps of the spectral power of magnetic fluctuations in the Pc5 band (1–10 mHz) and dTEC during substorms shows a good spatial and temporal correspondence between them. Both magnetic and ionospheric fluctuations tend to concentrate inside the auroral oval, the boundaries of which are determined from the OVATION model. The time–space evolution of TEC scintillations is rather similar to that of ultra-low-frequency magnetic fluctuations, but not to that of the ionospheric electrojet. GPS signal phase slips, resulting in non-physical TEC jumps (>1 TECu/min), occur predominantly inside the auroral oval and in the vicinity of its equatorward boundary. 相似文献
6.
Seppe Cassettari 《The Cartographic journal》2013,50(3):215-223
The British Cartographic Society has been in existence for 50 years. During that time it has sought to pursue its central aim of promoting the art and science of cartography through a variety of publications and events to its members and beyond. The Society has been on a journey of continual development in response to the way maps are created and used. In this short history we touch on some of the factors that have influenced its evolution and what the future may hold. 相似文献
7.
Rashmi Kandwal C. Jeganathan Valentyn Tolpekin S. P. S. Kushwaha 《Journal of the Indian Society of Remote Sensing》2009,37(2):275-290
Invasive species have been the focus of environmentalists due to their undesired impact on the ecosystem. Spread of Lantana
(Lantana camara L.), an invasive plant species, has been found in diverse geophysical environments causing a threat to the native flora.
Various eradication programmes have been attempted such as burning, chemical sprays, bio-control agents and physical plugging
mechanism for removing such invasive species in India. The efforts and success of these programmes need to be augmented with
a correct, quick and cost effective technique of mapping in order to locate them, understand their spatial extent and hence
make the process comprehensive. Also Lantana’s appearance as dense vegetation patches in remote sensing data causes problems
for estimating forest canopy density. Remote sensing provides a possible solution in qualitatively and quantitatively evaluating
terrestrial surface vegetation cover using spectral measure-ments. This research paper addresses issues and techniques adopted
to detect and extract Lantana, and can be used for various applications in forestry as well as in eradication programmes.
This study attempted to understand the appropriate band combination using Landsat data and generating vegetation indices in
order to extract Lantana patches in an accurate manner. Twenty nine different vegetation indices were analyzed for their effectiveness
in differentiating Lantana from other classes. The study showed that SAVI (Soil Adjusted Vegetation Index) is most favorable
in discriminating Lantana followed by Perpendicular Vegetation Index-3 in the optimum bio-window (February to April). 相似文献
8.
Orkan Özcan Bodo Bookhagen Nebiye Musaoğlu 《Journal of the Indian Society of Remote Sensing》2018,46(3):471-481
In this study, the spatial and temporal impacts of the Atatürk Dam on agro-meteorological aspects of the Southeastern Anatolia region have been investigated. Change detection and environmental impacts due to water-reserve changes in Atatürk Dam Lake have been determined and evaluated using multi-temporal Landsat satellite imageries and meteorological datasets within a period of 1984–2011. These time series have been evaluated for three time periods. Dam construction period constitutes the first part of the study. Land cover/use changes especially on agricultural fields under the Atatürk Dam Lake and its vicinity have been identified between the periods of 1984–1992. The second period comprises the 10-year period after the completion of filling up the reservoir in 1992. At this period, Landsat and meteorological time-series analyses are examined to assess the impact of the Atatürk Dam Lake on selected irrigated agricultural areas. For the last 9-year period from 2002 to 2011, the relationships between seasonal water-reserve changes and irrigated plains under changing climatic factors primarily driving vegetation activity (monthly, seasonal, and annual fluctuations of rainfall rate, air temperature, humidity) on the watershed have been investigated using a 30-year meteorological time series. The results showed that approximately 368 km2 of agricultural fields have been affected because of inundation due to the Atatürk Dam Lake. However, irrigated agricultural fields have been increased by 56.3% of the total area (1552 of 2756 km2) on Harran Plain within the period of 1984–2011. 相似文献
9.
Maps, created through the collection, assembly, and analysis of spatial data are used to support government planning and decision-making. Traditionally, spatial data used to create maps are collected, controlled, and disseminated by government, although over time, this role has shifted. This shift has been driven by the availability of alternate sources of data collected by private sector companies, and data contributed by volunteers to open mapping platforms, such as OpenStreetMap. In theorizing this shift, we provide examples of how governments use data sovereignty as a tool to shape spatial data collection, use, and sharing. We frame four models of how governments may navigate shifting spatial data sovereignty regimes; first, with government retaining complete control over data collection; second, with government contracting a third party to provide specific data collection services, but with data ownership and dissemination responsibilities resting with government; third, with government purchasing data under terms of access set by third party data collectors, who disseminate data to several parties, and finally, with government retreating from or relinquishing data sovereignty altogether. Within this rapidly changing landscape of data providers, we propose that governments must consider how to address data sovereignty concerns to retain their ability to control data use in the public interest. 相似文献
10.
The usefulness of remote sensing (RS), geographical information systems, and ground observations for monitoring changes in urban areas has been demonstrated through many examples over the last two decades. Research has generally focused on the relief phase following a disaster, but we have instead investigated the subsequent phases involving early recovery, recovery, and development. Our aim was to determine to what extent integration of the available tools, techniques, and methods can be used to efficiently monitor the progress of recovery following an earthquake. Changes in buildings within the Italian city of L’Aquila following the 2009 earthquake were identified from Earth observation data and are used as indicators of progress in the recovery process. These changes were identified through (1) visual analysis, (2) automated change detection using a set of decision rules formulated within an object-based image analysis framework, and (3) validation based on a combination of visual and semiautomated interpretations. An accuracy assessment of the automated analysis showed a producer accuracy of 81% (error of omission: 19%) and a user accuracy of 55% (error of commission: 45%). The use of RS made it possible for the identification of changes to be spatially exhaustive, and also to increase the number of categories used for a recovery index. In addition, using RS allowed the area requiring extensive fieldwork (to monitor the progress of the recovery process) to be reduced. 相似文献
11.
Cartographica incognita: ‘Dijital Jedis’, Satellite Salvation and the Mysteries of the ‘Missing Maps’ 总被引：1，自引：0，他引：1
Catherine Turk 《The Cartographic journal》2017,54(1):14-23
Like Participatory Geographic Information Systems (PGIS) and Public Participation Geographic Information Systems (PPGIS) crowdsourced collaborative mapping is often imagined as an alternative to conventional cartographic practice. This paper examines collaborative mapping projects designed to assist in humanitarian work and respond to catastrophes. These projects, their technological complexity and wide range of collaborators, including affected locals, international Non-Government Organisations (NGOs) and anonymous online contributors, invite closer consideration. In this article I unpick the gnarly question of how the remote sourcing of information through cloud collaboration and satellite imagery jostles with grounded work encouraging local control of local geoinformation. My critical analysis of these projects explores: (1) justifications for action – what is being promised through digital mapping as aid or satellite salvation?; (2) forms of participation – the role of ‘hotties’ ‘nodders’ and ‘digital jedis’; and (3) contingencies of mapping practices and the assemblages of actors within which they are embedded – as the mysteries of the ‘missing maps’. The conclusion considers differing approaches towards the inclusion of local knowledges within participatory digital aid mapping and identifies remote mapping practices that are both incognito and incognisant. 相似文献
12.
David Underwood 《GPS Solutions》1999,3(2):48-52
The use of the Global Positioning System (GPS) for position and attitude determination has been exploited for many years.
In these systems, it was required that multiple antennas maintained phase lock to common view satellites for long periods
of time in order to determine integer ambiguities. The challenge to overcome with the ballistic space probe is the high rotational
spin of this particular rocket. The antennas, mounted on the outside skin of the rocket, are in full view of each satellite
only for a fraction of a second before the rocket core eclipses them as it rotates. The antennas rarely see common satellites.
This article describes as system that overcomes these obstacles and provides position, acceleration, attitude, and rotation
rate. The approach uses a two-antenna system. One antenna is mounted either side of the rocket facing out. A hybrid tracking
channel combines signals from both antennas to overcome the signal blockage due to the rocket core as well as to defeat the
effect on the tracking channel due to the spin. The amplitude and phase of the spin rotation signature from each satellite
is extracted from the dual antenna data and used to compute the attitude and spin rate of the vehicle. ? 1999 John Wiley &
Sons, Inc. 相似文献
13.
none 《The Cartographic journal》2013,50(2):119-134
AbstractFighting the 1914–18 war largely on enemy territory in both the east and the west, German was at a disadvantage compared to the Allies when it came to survey and mapping as it did have access to much of the geodetic, topographic and cartographic data, relating to this terrain, necessary for modern warfare — in particular for artillery survey. German and Austria did, however, have a commanding lead in terrestrial and aerial photogrammetry, and the latter was to prove crucial in the production of accurate large-scale maps of enemy and occupied territory. Despite strong forces of conservatism in the high and field commands and in the artillery and military survey organizations, new air survey methods based on the photogoniometer and radial triangulation were rapidly developed. Through continual laboratory and field experimentation and testing, German was to increase her lead in aerial photogrammetry, and by the end of the war had not only set up a completely new air survey organization but was developing a new generation of optical-mechanical stereoplotting instruments of great precision. German progress was not, however, evident in all fields of military survey, and this paper examines the approaches taken by German to survey and mapping on the Western Front, and briefly compares and contrasts them with those of the Allies. 相似文献
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16.
S Kalyanaraman 《Journal of the Indian Society of Remote Sensing》1999,27(2):59-69
Under Indian Remote Sensing Satellite Programme, so far seven satellites have been launched to provide land, water, agricultural and Oceanographic information for resources monitoring and management under National Natural Resources Management System. The continuity of the data services is planned by way of providing improved multi-spectral data, panchromatic data, and oceanographic/atmospheric data, in the future also. The various errors in the satellite data namely radiometric and geometric errors which are to be corrected on ground before the data is put for use have been explained. The characteristics of the future satellites are also described in this article. 相似文献
17.
Geodetic measurements from 1963 through 1994 are used to estimate horizontal strain rates across the Red River fault near
Thac Ba, Vietnam. Whether or not this fault system is currently active is a subject of some debate. By combining: (1) triangulation
from 1963, (2) triangulation in 1983, and (3) Global Positioning System (GPS) observations in 1994, horizontal shear strain
rates are estimated without imposing any prior information on fixed stations. The estimated rates of shear strain in ten triangular
subnetworks surrounding the fault trace are not significantly different from zero at 95% confidence. The maximum rate of dextral
shear is less than 0.3 μrad/year in all but one of the triangles. The estimates help bound the slip rate in a simple elastic
dislocation model for a locked, vertical strike-slip fault. By assuming a locking depth of 5–20 km, the most likely values
for the deep slip rate are between 1 and 5 mm/year of right-lateral motion. These values delimit the 23% confidence interval.
At 95% confidence, the slip rate estimate falls between 7 mm/year of left-lateral motion and 15 mm/year of right-lateral motion.
Received: 18 November 1997 / Accepted: 28 January 1999 相似文献
18.
The Burhi‐Gandak river is one of the major tributaries of the Ganga River in the middle Ganga basin. The river is i known to have an oscillatory character and has changed its course in Recent times. In the present study, a variety of remote sensing data combined with surface and subsurface data have been used to delineate the fluvial palaeofeatures of this river. The palaeofeatures of the Burhi‐Gandak indicate that the river has shifted from N to S over a distance of 30 km. Further, its is observed that Burhi‐Gandak river had a larger channel width and higher discharge on earlier times and was very active. On detailed examination, a past link between the now northerly flowing Baghmati and Burhi‐Gandak rivers is detected. Based on the above features, three distinct stages of migration of the river have been identified and a summary of fluvial palaeohistory is presented. 相似文献
19.
Laurent Jégou 《制图学和地理信息科学》2013,40(2):182-188
ABSTRACTIn this article, we describe some ideas based on Bertin’s Sémiologie Graphique with a focus on extending it for aesthetic quality issues in cartography. We consider research in semiotics, aesthetics, and graphic design, with some fruitful results about the use of color or composition. We present several tools, oriented toward a pedagogical use and accessibility, helping to examine the color composition of an expressing image or to create meaningful gradients. While Bertin’s concepts still remain relevant and efficient, specific ideas can be developed further, to adapt to current media and gain from scientific advances from related disciplines. 相似文献
20.
Jeffrey D. Hamerlinck 《制图学和地理信息科学》2015,42(4):11-17
Popular and professional interest in maps and map-making has never been greater. Despite this engagement, introductory skills courses in “map use” have largely disappeared in undergraduate geography and cartography programs at US universities, with research indicating that both map-use course enrollments and the existence of such courses themselves are on the decline. While the map-use course and its content may have been replaced by, repackaged as, or incorporated into an integrated geographical information systems-cartography–remote sensing foundations course, how do we ensure that an understanding of maps and their unique characteristics is not lost in the mix? This essay describes a recent course redesign experience incorporating information literacy, technology fluency, and spatial thinking principles to maintain map-use concepts, skills, and appreciation in an introductory geographic information science and technology (GIS&T) foundations course, meeting both GIS&T and general education curricular goals. 相似文献