Photogeomorphological mapping of southern parts of Jadukata-Umngi river valleys,Meghalaya

Photogeomorphological mapping was carried out in parts of the lower reaches of the Jadukata-Umngi river valleys in the southern fringes of Meghalaya. The area has been divided into five geomorphic units. Topography in the area is controlled both by structure and lithology and the geomorphic features greatly facilitate in structural and lithological interpretation. This becomes quite evident from the photogeological map of the corresponding area.     

Satellite based mapping and morphogenetic analysis of the landforms in the tertiary fold belts of parts of Tripura,India

In the present study, satellite-based mapping and morphogenetic analysis of eastern part of Tripura has been attempted. Landforms are delineated based on conjugate analysis of satellite-imaged and satellite-derived digital elevation data. Further, landforms were classified based on hierarchical three-tier classification system where genesis is used as a criteria to classify the landforms in the first level followed by nature of their dissection and the geometric forms of the landform in second and third level, respectively. During the analysis, it has been observed that most of the landforms are structural in origin and their orientations are guided by the geological lineaments although the variations in the dissection pattern of the landforms are related to the changes in the underlying lithology. The implementation of quantitative analysis using hypsometric integral and ruggedness index of geomorphic parameters indicates that the landforms are immature but have been evolving towards maturity.     

A note on adjustment of free networks

The present paper deals with the least-squares adjustment where the design matrix (A) is rank-deficient. The adjusted parameters \(\hat x\) as well as their variance-covariance matrix ( \(\sum _{\hat x} \) ) can be obtained as in the “standard” adjustment whereA has the full column rank, supplemented with constraints, \(C\hat x = w\) , whereC is the constraint matrix andw is sometimes called the “constant vector”. In this analysis only the inner adjustment constraints are considered, whereC has the full row rank equal to the rank deficiency ofA, andAC ^T =0. Perhaps the most important outcome points to the three kinds of results

1. A general least-squares solution where both \(\hat x\) and \(\sum _{\hat x} \) are indeterminate corresponds tow=arbitrary random vector.
2. The minimum trace (least-squares) solution where \(\hat x\) is indeterminate but \(\sum _{\hat x} \) is detemined (and trace \(\sum _{\hat x} \) corresponds tow=arbitrary constant vector.
3. The minimum norm (least-squares) solution where both \(\hat x\) and \(\sum _{\hat x} \) are determined (and norm \(\hat x\) , trace \(\sum _{\hat x} \) corresponds tow?0

     

A note on Earth's rotation angular velocity in the general-relativity framework

 The value of the Earth's rotational angular velocity determined from observations is given in the GCRS (geocentric celestial reference system) defined by Resolution B1 of the 2000 IAU General Assembly. The same quantity derived from dynamical theories of the Earth's rotation, such as SMART97, is referred to the␣DGRSC (dynamically non-rotating ecliptical reference system). The relativistic theory of reference systems (RSs) enables unambiguous general-relativity relations between these quantities to be derived. Received: 9 November 2000 / Accepted: 9 July 2001     

从地理规律到地理空间人工智能EI北大核心CSCD

近年来,人工智能技术快速发展,影响了很多学科的研究范式。对于地理学而言,这种趋势也不例外。从知识发现的角度,地理学研究主要有两个任务,即揭示未知的具体事实和发现一般性的规律机理。在这两个方面,人工智能技术可帮助地理学家发现知识甚至自动提取知识。相对于地球科学其他学科,地理学自动提取知识的任务更为凸显。但是在寻求地理规律的过程中,需要处理一般性和地理异质性之间的权衡,其核心可以表述为人工智能学习过程中的基础问题:泛化及可解释性问题。因此,二者存在内在的逻辑一致性,积极引入人工智能技术有助于强化地理学的学科基础。本文通过实例给出了人工智能用于地理规律发现的一个简单框架,指出了未来地理空间人工智能发展的方向,以及地理信息科学在机制、模型、方法及应用方面潜在的新任务。     

A brief note on remote sensing activities in Nigeria

Abstract

Orbital photography from the Space Shuttle missions (1981–88) and earlier manned spaceflight programs (1962–1975) allows remote sensing time series to be constructed for observations of environmental change in selected portions of the global tropics. Particular topics and regions include deforestation, soil erosion, supersedimentation in streams, lacustrine, and estuarine environments, and desertification in the Greater Amazon, Tropical Africa and Madagascar, South &; Southeast Asia, and the Indo‐Pacific archipelagoes.     

Analysis and classification of hyperspectral data for mapping land degradation: An application in southern Spain

Desertification is a severe stage of land degradation, manifested by “desert-like” conditions in dryland areas. Climatic conditions together with geomorphologic processes help to mould desert-like soil surface features in arid zones. The identification of these soil features serves as a useful input for understanding the desertification process and land degradation as a whole. In the present study, imaging spectrometer data were used to detect and map desert-like surface features. Absorption feature parameters in the spectral region between 0.4 and 2.5 μm wavelengths were analysed and correlated with soil properties, such as soil colour, soil salinity, gypsum content, etc. Soil groupings were made based on their similarities and their spectral reflectance curves were studied. Distinct differences in the reflectance curves throughout the spectrum were exhibited between groups. Although the samples belonging to the same group shared common properties, the curves still showed differences within the same group.Characteristic reflectance curves of soil surface features were derived from spectral measurements both in the field and in the laboratory, and mean reflectance values derived from image pixels representing known features. Linear unmixing and spectral angle matching techniques were applied to assess their suitability in mapping surface features for land degradation studies. The study showed that linear unmixing provided more realistic results for mapping “desert-like” surface features than the spectral angle matching technique.     

大比例尺地形图测绘项目的集成管理研究

本文应用项目集成管理的方法,研究大比例尺地形图测绘过程中如何提高整体效益的问题:结合大比例尺地形图测绘的特点,不但建立测绘项目的成本、工期、质量三要素集成网络计划模型,引入遗传算法对模型进行优化求解,并且对测绘项目风险进行预测,探索了一种兼顾成本、工期、质量和风险四个要素的测绘项目集成管理方法.风险因素与其他三要素的集...     

A note on the computation of Meissl’s smoothing coefficients βℓ

This note gives a new, short and non-recursive formula for Meissl’s smoothing coefficients β_?.     

海岸线及其测绘技术探讨

海岸线是人类所使用的最古老的边界线之一,然而,由于其动态特征,加之当今社会对海岸带的需求越来越多,这条边界线的位置存在争议,因而,如何使用客观手段测绘海岸线尤为重要。文中针对海岸线定义及其位置确定不明确的现状,指出海岸线定义存在的问题,给出完善定义的意见;分析海岸线常规的测绘方法,探讨海岸线精确测绘的新方法和技术。     

A note on the avulsion of ranga river,district north Lakhimpur,Assam

Ranga river, a major tributary of the Subanslri on the north bank of Brahmaputra exhibits the phenomenon of avulsion which has occured in the recent past. Avulsion has resulted primarily due to the building up of an alluvial ridge to the east.     

基于AJAX的Internet地图服务方法初探

2005年,AJAX技术被提出并开始成熟,已经迅速走向实际应用。短短1年间,基于AJAX技术的Intenet地图服务如雨后春笋般涌起,如Google Maps、百度地图、搜狗地图、Yahoo Maps和MSN Virtual Earth等。本文首先分析了Intetnet地图服务现状——人们对地图服务需求迫切和地图服务不够快速友好的矛盾,并简单介绍了AJAX技术及其优点,在此基础上,初步探讨了基于AJAX的Internet地图服务方法的相关原理,给出了地图服务框架,并简单讨论了地图服务AJAX引擎包含的若干对象,最后分析了其优势和前景,并对地理信息服务的发展方向进行了思考。     

A vector and raster graphic mapping tool on micro-computers

Abstract

The rapid development of physically-based hydrological information and modelling systems has necessitated enhanced data entry and display systems. A 'mapping tool' is developed for the manipulation and display of spatial information, which is a cost-efficient, self-contained utility system that is suitable for use on micro-computers. It has the ability to be integrated as part of any modelling or information system. Diverse applications using the 'mapping tool' are briefly described including resource management systems for planners, mass balance studies in urban catchments and data entry systems for physically based models.     

A note on frame transformations with applications to geodetic datums

Rigorous equations in compact symbolic matrix notation are introduced to transform coordinates and velocities between ITRF frames and modern GPS-based geocentric geodetic datums. The theory is general but, after neglecting higher than second-order terms, it is shown that the equations revert to the formulation currently applied in most major continental datums. We discuss several examples: the North American Datum of 1983 (NAD83), the European Terrestrial Reference System of 1989 (ETRS89), the Geodetic Datum of Australia of 1994 (GDA94), and the South American Geocentric Reference System (SIRGAS). Electronic Publication     

An assessment on the use of Terra ASTER L3A data in landslide susceptibility mapping

The main purpose of the present study is to evaluate the potential use of Terra ASTER data—the L3A DEM and its derivatives in landslide susceptibility mapping. For the purpose, an appropriate application site from the Western Black Sea region of Turkey—the Kelemen catchment area was selected. During the analyses, a two-stage comparative evaluation was carried out. In the first stage, the differences between the DEMs obtained from Terra ASTER L3A data and the conventional topographic data; and their first and second derivatives were investigated. Subsequently, different susceptibility maps were produced by using the DEMs and the topographic attributes obtained from both source of data in addition to the spectral information acquired from satellite sensor. According to the results of the comparative evaluations, a strong correlation between Terra ASTER L3A DEM and the conventional topographic data was obtained. However, depending on the increment of the degree of the derivative, an evident decrease in the spatial correlations was observed. On the contrary, the final model performance, prediction capacity, and the spatial performance statistics for the landslide susceptibility maps produced by using both source of data were found as very high and close to each other.     

A forestry GIS-based study on evaluating the potential of imaging spectroscopy in mapping forest land fertility

Fertility, or the availability of nutrients and water, controls forest productivity. It affects its carbon sequestration, and thus the forest's effect on climate, as well as its commercial value. Although the availability of nutrients cannot be measured directly using remote sensing methods, fertility alters several vegetation traits detectable from the reflectance spectra of the forest stand, including its pigment content and water stress. However, forest reflectance is also influenced by other factors, such as species composition and stand age. Here, we present a case study demonstrating how data obtained using imaging spectroscopy is correlated with site fertility. The study was carried out in Hyytiälä, Finland, in the southern boreal forest zone. We used a database of state-owned forest stands including basic forestry variables and a site fertility index. To test the suitability of imaging spectroscopy with different spatial and spectral resolutions for site fertility mapping, we performed two airborne acquisitions using different sensor configurations. First, the sensor was flown at a high altitude with high spectral resolution resulting in a pixel size in the order of a tree crown. Next, the same area was flown to provide reflectance data with sub-meter spatial resolution. However, to maintain usable signal-to-noise ratios, several spectral channels inside the sensor were combined, thus reducing spectral resolution. We correlated a number of narrowband vegetation indices (describing canopy biochemical composition, structure, and photosynthetic activity) on site fertility. Overall, site fertility had a significant influence on the vegetation indices but the strength of the correlation depended on dominant species. We found that high spatial resolution data calculated from the spectra of sunlit parts of tree crowns had the strongest correlation with site fertility.