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1.
Abstract

Riparian vegetation has a fundamental influence on the biological, chemical and physical nature of rivers. The quantification of riparian landcover is now recognised as being essential to the holistic study of the ecosystem characteristics of rivers. Medium resolution satellite imagery is now commonly used as an efficient and cost effective method for mapping vegetation cover; however such data often lack the resolution to provide accurate information about vegetation cover within riparian corridors. To assess this, we measure the accuracy of SPOT multispectral satellite imagery for classification of riparian vegetation along the Taieri River in New Zealand. In this paper, we discuss different sampling strategies for the classification of riparian zones. We conclude that SPOT multispectral imagery requires considerable interpretative analysis before being adequate to produce sufficiently detailed maps of riparian vegetation required for use in stream ecological research.  相似文献   

2.
《The Cartographic journal》2013,50(4):321-328
Abstract

Map generalisation is an abstraction process that seeks to transform the representation of cartographic objects from the original version into a coarser one. The characteristics of cartographic objects and the arrangement of map features have to be observed and preserved in a generalisation process. A method is developed for typifying drainages while preserving their structural characteristics, i.e.presenting the drainages with reduced number of rivers under the constraint of preserving the original structure in terms of the type and distribution of the rivers. We apply Töpfer's radical law to calculate the amount of the rivers to be retained on the generalised map. The drainages share the amount of retained rivers in proportion to the number of their tributaries. In each of the drainages, the shared amount is divided among the rivers based on the dendritic decomposition of the drainage. We implement and test the method in Java Environment. Results from case studies show that the method effectively preserves the original structures of the drainages on the generalised maps.  相似文献   

3.
Abstract

Virtual Australia is not a well-defined or agreed concept. This discussion paper conceptualises Virtual Australia as a ‘virtual [digital] model containing and representing all non-trivial objects and their contextual environment – from blue sky to bedrock – in real world Australia’. It describes a scenario for Virtual Australia, one or two decades from now, in which the locations and conditions of non-trivial objects and their environment are updated automatically through a combination of remote sensing and wireless communication technologies in support of a ‘Supranet’. It then examines the concept of the ‘Supranet’ – a pervasive information network based largely on wireless technology linking the physical world to a virtual model in real time – and develops and discusses three principal characteristics of the Supranet: the ability to have or collect specific information (know); the ability to process information (think); and the ability to communicate that information. If, in the near future, any or all non-trivial devices are to some extent able to know, think and communicate, the potential for object autonomy will be realised.  相似文献   

4.
The author develops a criterion for assessment of the quality of projections used for world maps which incorporates measures of mean square distortions of line lengths in principal directions about a point and the relationship of angular and areal distortion (in equal measure, or depending upon the requirements of particular types of maps). Translated from: Izvestiya vysshykh uchebnykh zavedeniy, Geodeziya i aerofotos”yemka, 1987, No. 3, pp. 109-112.  相似文献   

5.
《测量评论》2013,45(6):284-287
Abstract

In the survey world of Northern Rhodesia the most notable event in 1931 (apart, of course, from the birth of this Review) has been the completion of the aerial survey contracts undertaken for the Government by the Aircraft Operating Company. The results have justified expectations particularly with regard to the mapping of 63,000 square miles of the Territory on a scale of 1/250,000. Used in conjunction with the information obtained by ground methods by the Mining Companies, who have kindly consented to put their information at our disposal, a really reliable detailed map of a considerable portion of the Territory should be obtained. The mosaics of the six principal townships are also proving of value and contain a wealth of detail which would be difficult to obtain so accurately by ground survey except at great expense. On the other hand it is obvious that it would be a costly business involving a very large amount of ground control to prepare a closely contoured plan such as is required for detail purposes in connection with township lay-outs.  相似文献   

6.
Abstract

Cartography in general, and building solid landscape models in particular, requires an interdisciplinary set of skills in order to be done well. Traditional handcrafted construction methods provide quality results, but are extremely labour-intensive and therefore costly. Modern methods using digital terrain models (DTMs) and computer numerical control (CNC) milling are fast and accurate, but the finished models are visually less than optimal. Solutions are proposed using DTMs and CNC milling to create landscape models in which the initial shaping is done mechanically and the fine details are carved by hand. This ‘balanced approach’ to landscape modelling combines the time- and cost-advantages of modern digital technology with the quality of traditional handcrafted techniques resulting in highly accurate landscape models which still retain the artistic ‘feel’ of the human touch.  相似文献   

7.
ABSTRACT

The challenge of enabling syntactic and semantic interoperability for comprehensive and reproducible online processing of big Earth observation (EO) data is still unsolved. Supporting both types of interoperability is one of the requirements to efficiently extract valuable information from the large amount of available multi-temporal gridded data sets. The proposed system wraps world models, (semantic interoperability) into OGC Web Processing Services (syntactic interoperability) for semantic online analyses. World models describe spatio-temporal entities and their relationships in a formal way. The proposed system serves as enabler for (1) technical interoperability using a standardised interface to be used by all types of clients and (2) allowing experts from different domains to develop complex analyses together as collaborative effort. Users are connecting the world models online to the data, which are maintained in a centralised storage as 3D spatio-temporal data cubes. It allows also non-experts to extract valuable information from EO data because data management, low-level interactions or specific software issues can be ignored. We discuss the concept of the proposed system, provide a technical implementation example and describe three use cases for extracting changes from EO images and demonstrate the usability also for non-EO, gridded, multi-temporal data sets (CORINE land cover).  相似文献   

8.
Abstract

The analysis of remote sensing (RS) images, which is often accomplished using unsupervised image classification techniques, requires an effective method to determine an appropriate number of classification clusters. This paper proposes a preliminary analytical method to evaluate the input parameters for unsupervised RS image classification. Our approach involves first analysing the colour spaces of RS images based on the human visual perception theory. This enables the initial number of clusters and their corresponding centres to be automatically established based on the interaction of different forces in our supposed force field. The proposed approach can automatically determine the appropriate initial number of clusters and their corresponding centres for unsupervised image classification. A comparison of the experimental results with those of existing methods showed that the proposed method can considerably facilitate unsupervised image classification for acquiring accurate results efficiently and effectively without any prior knowledge.  相似文献   

9.
Abstract

The rapid and accurate grasp of changes in residences is crucial for urban planning and urbanisation. However, the traditional methods for extracting residences exists several problems, which lead to inaccurate extraction results. In this study, the Landsat image is used to establish a new method for extracting the residences quickly and accurately. The specific steps are as follows: (1) We calculate surface albedo to exclude the interference of waters and shadows; (2) Using single-band threshold method, we eliminate the interference of shadows; (3) Normalized Difference Vegetation Index is calculated to exclude the effects of vegetation; (4) Roads are removed by calculating the shape index. Verification shows that the accuracy of this extraction method is 92.81%, which is more accurate than the traditional methods and solves the problems existed in the traditional methods. This novel method is a new reference for other land cover research on the technical aspect.  相似文献   

10.
《测量评论》2013,45(1):21-24
Abstract

The function of a compass is to indicate the direction of the magnetic field in its neighbourhood. Its pointing is therefore magnetic not geographical. The divergence from a true-north indication, different in different parts of the world, is the “variation” of the compass. This quantity is obviously of importance for true directional work when the magnetic compass is used. Its value is known to a high degree of accuracy and is easily available. Such accurate magnetic data are obtained from an elaborate and special form of compass known as a “Magnetometer” and are regularly published by the Astronomer Royal to an accuracy of about half a minute of arc.  相似文献   

11.
Abstract

Estimation of snowmelt runoff is very important in the Western Himalayan rivers in India where it is required to plan for hydropower generation and the water management during the non‐monsoon season. An attempt has been made to estimate snowmelt runoff on a 10 day average basis in Beas Basin up to Pandoh Dam during May, 1998 and November, 1999 using a Snowmelt Runoff Model (SRM), which is a degree day method. The input parameters for the model are derived from existing maps, satellite data, metrological and hydrological data. The relief of the basin is divided into 12 elevation zones of 500 m each. The temperature was extrapolated to these elevation zones using temperature lapse rate calculated using the observed temperature at seven stations within the basin. Snow covered area in the basin was determined using Indian Remote Sensing Satellites IRS ‐ 1C / 1D Wide Field Sensor (WIFS). The runoff from the snow covered area and snow free area was separately calculated in each elevation zone. The model parameter degree‐day factor is taken from literature and runoff coefficients for snow and rain are derived using the observed data. The total discharge at the dam site is computed by a weighted sum of runoff components from all the elevation zones. There is a good agreement between the observed and computed runoff with a coefficient of determination of 0.854 and the difference in volume is + 4.6 %.  相似文献   

12.
《测量评论》2013,45(81):118-128
Abstract

Surveying tapes of steel are much more satisfactory mechanically than those of invar, and are less subject to secular changes of length, but the magnitude of their coefficient of thermal expansion demands a closer knowledge of their temperature than can be obtained with ordinary thermometers suspended near the tapes. The measurement of steel tapes in terms of their electrical resistance has therefore been investigated. The history of this work is traced. The use of resistance methods has proved satisfactory in the field, and under Laboratory conditions at the N.P.L. the accuracy of 1 part in 2 millions in the measurement of the lengths of 24-metre and 100-foot tapes of steel is attained. Such steel tapes appear to have remained stable on the average within about 2 parts in a million in 25 years.  相似文献   

13.
《测量评论》2013,45(43):271-273
Abstract

I Commenced this experiment many years ago, and other persons in various parts of the world have since tested it abroad. By far the greater number of their results are quite satisfactory.  相似文献   

14.
Suspended sediment yield is a very important environmental indicator within Amazonian fluvial systems, especially for rivers dominated by inorganic particles, referred to as white water rivers. For vast portions of Amazonian rivers, suspended sediment concentration (SSC) is measured infrequently or not at all. However, remote sensing techniques have been used to estimate water quality parameters worldwide, from which data for suspended matter is the most successfully retrieved. This paper presents empirical models for SSC retrieval in Amazonian white water rivers using reflectance data derived from Landsat 5/TM. The models use multiple regression for both the entire dataset (global model, N = 504) and for five segmented datasets (regional models) defined by general geological features of drainage basins. The models use VNIR bands, band ratios, and the SWIR band 5 as input. For the global model, the adjusted R2 is 0.76, while the adjusted R2 values for regional models vary from 0.77 to 0.89, all significant (p-value < 0.0001). The regional models are subject to the leave-one-out cross validation technique, which presents robust results. The findings show that both the average error of estimation and the standard deviation increase as the SSC range increases. Regional models were more accurate when compared with the global model, suggesting changes in optical proprieties of water sampled at different sampling stations. Results confirm the potential for the estimation of SSC from Landsat/TM historical series data for the 1980s and 1990s, for which the in situ database is scarce. Such estimates supplement the SSC temporal series, providing a more comprehensive SSC temporal series which may show environmental dynamics yet unknown.  相似文献   

15.
《The Cartographic journal》2013,50(3):243-253
Abstract

Indigenous people throughout the world developed their own mapping skills and systems of knowledge. While Westerners are prone to overlook these communities' geographical knowledge and imagine their mapping activities to be primitive or non-existent, their mental maps are often impressive in sophistication and detailed even if based on cosmologies that are quite foreign to Western thinking. This article depicts a mental map of the ocean floor shared by Polynesians of Anuta, a remote community in the Solomon Islands. It situates Anuta's reef map in relation to academic discussions of indigenous cartography and describes the process that resulted in the map's physical representation.  相似文献   

16.
Abstract

The Electronic Chart and the Electronic Chart Display Information System are integrating technologies requiring accurate position fixing using GPS, assessment of current sea surface situation using radar and high quality display in map form. The latter aspect is addressed here with an emphasis on operational requirements for such shipboard cartography including colour and symbolisation.  相似文献   

17.
《The Cartographic journal》2013,50(3):225-231
Abstract

This paper is about different worlds, and how we try to unite them. One of these worlds is the world of National Atlases: collections of complex, high-quality maps presenting a nation to the geographically interested. The second is the world of National Spatial Infrastructures: highly organized, standardized and institutionalized large collections of spatial data and services. In the paper, we describe the two worlds and their fundamental differences and we present the theoretical framework in which these worlds could be united. We introduce a test bed we are using to try out the theoretical framework in a real-life use case. In the architecture of that test bed, we introduce a National Atlas Services layer and describe how we have created an Atlas Map Viewer component, using the Open Web Platform. We conclude by commenting on the results thus far and taking a look into future developments.  相似文献   

18.
董震  杨必胜 《测绘学报》2015,44(9):980-987
提出了一种从车载激光扫描数据中层次化提取多类型目标的有效方法。该方法首先利用颜色、激光反射强度、空间距离等特征,生成多尺度超级体素;然后综合超级体素的颜色、激光反射强度、法向量、主方向等特征利用图分割方法对体素进行分割;同时计算分割区域的显著性,以当前显著性最大的区域为种子区域进行邻域聚类得到目标;最后结合聚类区域的几何特性判断目标可能所属的类别,并按照目标类别采用不同的聚类准则重新聚类得到最终目标。试验结果表明,该方法成功地提取出建筑物、地面、路灯、树木、电线杆、交通标志牌、汽车、围墙等多类目标,目标提取的总体精度为92.3%。  相似文献   

19.
Abstract

Hydrology and Water Management are key areas of applied science in the current world economy. Increasingly hydrologiste are looking to satellite remote sensing to help meet their needs for near real‐time data to measure, monitor and model water in the environment. However, progress has been hindered by the lack of a dedicated series of hydro‐logical satellites.

The paper summarises studies undertaken on an international basis in order to influence satellite, sensor and ground segment design operations to suit the needs of water management.  相似文献   

20.
Abstract

A super-resolution enhancement algorithm was proposed based on the combination of fractional calculus and Projection onto Convex Sets (POCS) for unmanned aerial vehicles (UAVs) images. The representative problems of UAV images including motion blur, fisheye effect distortion, overexposed, and so on can be improved by the proposed algorithm. The fractional calculus operator is used to enhance the high-resolution and low-resolution reference frames for POCS. The affine transformation parameters between low-resolution images and reference frame are calculated by Scale Invariant Feature Transform (SIFT) for matching. The point spread function of POCS is simulated by a fractional integral filter instead of Gaussian filter for more clarity of texture and detail. The objective indices and subjective effect are compared between the proposed and other methods. The experimental results indicate that the proposed method outperforms other algorithms in most cases, especially in the structure and detail clarity of the reconstructed images.  相似文献   

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