从GIS与GPS的数据处理问题看近代平差的发展方向

随着测绘新技术的发展,测量工已经发展到新的近代平差阶段,而“３Ｓ”技术的迅速发展更进一步推动了近代平差的发展。本文通过简单介绍了ＧＩＳ空间数据的误差分析和平差模型,以及ＧＰＳ基线向量观测值的选择,整周未知数的求解和动态ＧＰＳ的卡尔曼滤波等,来说明测绘新技术与近代平差的相互推动作用,并论述近代平差的发展方向,同时,对近代平差发展中的几个值得商榷的问题提出了看法。     

GIS Implementation in Developing Countries: Learning from Organisational Theory and Reflective Practice

Both Geographic Information Systems (GIS) implementation successes and failures can be attributed to many factors, some that have little or nothing to do with the technology. While the discourse in the developed world has shifted from examining GIS implementation in isolation, developing countries appear to be still bogged down by many institutional barriers that impede implementation. In this context, an integrative implementation framework that takes into consideration politics and policy issues is developed to understand, explain, and assess GIS implementation in developing countries. The uniqueness of country-specific problems is acknowledged and juxtaposed against a body of theory in order to evaluate GIS implementation efforts. Based on reflective accounts of implementation efforts in three developing countries, four overarching characteristics of successful GIS implementation across country contexts are identified. These include clarity in problem definition, forging strategic alliances, incremental planning, and developing local knowledge. GIS implementation is likely to occur only when individuals and organisations creatively challenge existing norms, organisational defensive routines, and inefficient bureaucratic practices. Therefore, successful GIS implementation in developing countries is a likely outcome of critical reflective practice that relies on the capacity of empowered individuals and groups rather than solely on organisational structures.     

Preservation of Spatial Information in Rasterization Processes: A Practical Approach Using Real Categorical Data and Landscape Metrics

Rasterization (i.e., vector-to-raster conversion) is a common process in geographic information systems. As it implies redistribution of map information, it is important to know how much data are lost when a particular resolution is chosen, in order to use data successfully. This study explores the potential of landscape metrics to reflect sensitivity to rasterization processes. A vectorial land use map was rasterized to an array of cell sizes. Deviation from original data was estimated, and landscape metrics were calculated for each land cover class. Results allowed grouping of classes—with respect to how information was preserved—depending on their landscape characteristics.     

基于遥感和GIS的辅助规划模型--以珠江三角洲可持续土地开发为例

提出利用遥感和 Ｇ Ｉ Ｓ来获得合理的城市发展布局和减少浪费土地资源的新方法。该模型是根据环境经济学资源分配原理和可持续发展理论,通过遥感和 Ｇ Ｉ Ｓ的结合来实现。模型的核心就是保证在时间和空间上合理地安排土地资源。由此评价了珠江三角洲东莞市近年来的土地开发,获得了有意义的结果。并通过模型的运算,给出了规划期内的土地利用的优化方案,以减少浪费土地资源的现象。     

Non-point source pollution in Indian agriculture: Estimation of nitrogen losses from rice crop using remote sensing and GIS

The paper presents a detailed understanding of nitrogenous fertilizer use in Indian agriculture and estimation of seasonal nitrogen loosses from rice crop in Indo-Gangetic plain region, the ‘food bowl’ of the Indian sub-continent. An integrated methodology was developed for quantification of different forms of nitrogen losses from rice crop using remote sensing derived inputs, field data of fertilizer application, collateral data of soil and rainfall and nitrogen loss coefficients derived from published nitrogen dynamics studies. The spatial patterns of nitrogen losses in autumn or ‘kharif’ and spring or ‘rabi’ season rice at 1 × 1 km grid were generated using image processing and GIS. The nitrogen losses through leaching in form of urea-N, ammonium-N (NH₄-N) and nitrate-N (NO₃-N) are dominant over ammonia volatilization loss. The study results indicate that nitrogen loss through leaching in kharif and rabi rice is of the order of 34.9% and 39.8% of the applied nitrogenous fertilizer in the Indo-Gangetic plain region. This study provides a significant insight to the role of nitrogenous fertilizer as a major non-point source pollutant from agriculture.     

Effect of Forest Fire on Snow Reflectance in Uttarakhand Region: An Analysis Using AWiFS and INSAT-3D Data

In the summer of 2016, fire broke out in the forests of Uttarakhand state. The effect of forest fire was thought to have severe impact on nearby glaciated region in terms of faster melting. It is understood that contamination and heat enhance the snowmelt, which reduces the reflectance in different part of EM spectrum. In order to assess the effect, AWiFS and IMAGER data from Resourcesat-1 and INSAT-3D, respectively, for the months of April and May of the years 2012, 2013, 2014 and 2016 were used to compare the reflectance of snow. It was observed that pre- and post-fire data of 2016 show drop in reflectance in comparison with earlier years. The change in reflectance for locations near to forest fire was significantly high in comparison with previous year images, whereas far-away locations did not show much change. This drastic drop may be attributed to deposition of black carbon on nearby locations in snow-covered area. AWS data of nearby Joshimath observatory were also analysed to avoid any anomalous change in temperature for the same duration.     

Retrieval of CDOM and DOC Using In Situ Hyperspectral Data: A Case Study for Potable Waters in Northeast China

Chromophoric dissolved organic matter (CDOM), the light absorbing fraction of dissolved organic carbon (DOC), together with phytoplankton and total suspended matter are the main optically active components could be retrieved by remote sensing data. Generally, different composition of DOC and CDOM corresponds to different water surface reflectance. Absorption properties of CDOM and retrieval models for CDOM and DOC were investigated with data from potable reservoirs located in the central of Jilin Province. Water sampling field surveys were conducted on 15, 16 and 19 of September 2012 across the Shitoukoumen, Erlonghu and Xilicheng reservoirs, respectively. Both empirical regression (single band model and band ratio model) and partial least squares coupled with back-propagation artificial neural models (PLSBPNN) were established to estimate CDOM absorption coefficient at 355 nm [a_CDOM(355)] and DOC concentration with in situ measured remote sensing reflectance. It was found that the band ratio models and PLSBPNN model performed well for estimating DOC concentration while the band ratio models yielded the best result in retrieval CDOM. Moreover, all the three models performed better on the DOC concentration estimation than the performance on a_CDOM(355). Band ratio models outperformed (R ² ?=?0.55) other models for estimating CDOM absorption coefficient, while PLSBPNN model outperformed other models with respect to DOC estimation (R ² ?=?0.93). High spectral slope values indicated that CDOM in the potable waters primarily comprised low molecular weight organic substances; while sources of DOC were mainly coming from exogenous input, which was the main reason lead to the difference of model performances on DOC and a_CDOM(355) estimation. The algorithms developed in this study is needed to be tested and refined with more in situ spectral data, also future work is still needed to be undertaken for characterizing the dynamic of the potable water quality with remotely sensed imagery.     

ArcMAP中利用TIN检查1：5万DLG数据等高线点线矛盾的方法探讨

通过对国家I:5万DLG更新数据的生产实践,提出在ArcMAP中利用TIN检查1:5万DLG数据等高线点线矛盾的方法,文中详细探讨了检查的基本原理、思路以及在VB.NET中代码实现的过程.     

Soil Loss Mapping for Sustainable Development and Management of Land Resources in Warora Tehsil of Chandrapur District of Maharashtra: An Integrated Approach Using Remote Sensing and GIS

The study area is characterized by low and fluctuating rainfall pattern, thin soil cover, predominantly rain-fed farming with low productivity coupled with intensive mining activities, urbanization, deforestation, wastelands and unwise utilization of natural resources causing human induced environmental degradation and ecological imbalances, that warrant sustainable development and optimum management of land resources. Spatial information related to existing geology, land use/land cover, physiography, slope and soils has been derived through remote sensing, collateral data and field survey and used as inputs in a widely used erosion model (Universal Soil Loss Equation) in India to compute soil loss (t/ha/yr) in GIS. The study area has been delineated into very slight (<5 t/ha/yr), slight (5–10 t/ha/yr), moderate (10–15 t/ha/yr), moderately severe (15–20 t/ha/yr), severe (20–40 t/ha/yr) and very severe (>40 t/ha/yr) soil erosion classes. The study indicate that 45.4 thousand ha. (13.7% of TGA) is under moderate, moderately severe, severe and very severe soil erosion categories. The physiographic unit wise analysis of soil loss in different landscapes have indicated the sensitive areas, that has helped to prioritize development and management plans for soil and water conservation measures and suitable interventions like afforestation, agro-forestry, agri-horticulture, silvipasture systems which will result in the improvement of productivity of these lands, protect the environment from further degradation and for the ecological sustenance.     

Spatially Explicit Estimation of Leaf Area Index Using EO-1 Hyperion and Landsat ETM+ Data: Implications of Spectral Bandwidth and Shortwave Infrared Data on Prediction Accuracy in a Tropical Montane Environment

This study evaluated the utility of narrowband (EO-1 Hyperion) and broadband (Landsat ETM+) remote sensing data for the estimation of leaf area index (LAI) in a tropical environment in Sulawesi, Indonesia. LAI was inferred from canopy gap fraction measurements taken in natural tropical forest and cocoa plantations. Single and multiple spectral bands and spectral indices were used as predictor variables in reduced major axis (RMA) and ordinary least squares (OLS) regression models. The predictive power of most regression models was notably higher when employing narrowband data instead of broadband data. Highly significant relationships between LAI and spectral reflectance were observed near the red-edge region and in most shortwave infrared (SWIR) bands. In contrast to most near-infrared (NIR) narrow bands, the correlation between SWIR reflectance and LAI was not confounded when including both vegetation types and did not suffer from saturation. The results demonstrate that leaf area index of a challenging tropical environment can be estimated with satisfactory accuracy from hyperspectral remote sensing data.     

Using remotely sensed data for census surveys and population estimation in developing countries: examples from Nigeria

"Using examples from Nigeria, this paper demonstrates how remotely sensed data can be used to acquire some of the basic data requirements for census surveys and to estimate population. The result obtained shows that visual identification of settlements on Landsat MSS and TM is more accurate and economical than equivalent digital classification techniques. Black and white aerial photographs were used to estimate the population of a model town and to establish EAs [enumeration areas]. The population estimation method employed can be used to obtain intercensal population estimates for the rapidly growing central places, while the established EAs for the study area have created a permanent base for future census surveys and census cross-validation, population estimation and other social surveys."     

The Geography,Structure, and Evolution of the GIS Research Community in the US: A Network Analysis from 1992 to 2011

The research community of Geographic Information Systems and Science (GIS) has been growing rapidly during the last two decades. Little attention has been paid to understanding its geography, structure and evolution. Taking a new organizational perspective, this article aims to fill the knowledge gap by analyzing collaboration and citation networks between GIS research organizations, including academic institutions, government agencies, businesses, and others. These two networks are analyzed in geographical and bibliographical spaces, respectively, to discover characteristic distributions and structures. The results show an uneven geographic distribution of GIS research organizations, and clustered spatial interactions between them. Both collaboration and citation networks exhibit typical “scale‐free” structures, which came into being around the year 2000 and have remained to the present. Further, the GIS research community is composed of 11 cohesive sub‐groups, with each having a clear hub‐spoke structure and a few highly connected organizations as leaders. These results shed light on the overall picture of the GIS research community, and offer a reference system that stimulates further exploration.     

Groundwater potential in the hard rock terrain of western ghats: A case study from Kottayam district,Kerala using resourcesat (IRS-P6) data and GIS techniques

The present study was aimed to identify and delineate the groundwater potential areas in parts of Western Ghats, Kottayam, covering the upper catchment of Meenachil river. The study area is composed rocks of Archaean age and Charnockite dominated over others. The information on lithology, geomorphology, lineaments, slope and land use/land cover was generated using the Resourcesat (IRS P6 LISS III) data and Survey of India (Sol) toposheets of scale 1:50,000 (surveyed in 1969) and integrated them with raster based Geographical Information System (GIS) to identify the groundwater potential of the study area. Thus, a GIS-based model which takes account of local condition/variations has been developed specifically for mapping groundwater potential. On the basis of hydrogeomorphology, three categories of groundwater potential zones namely good, moderate and poor were identified, and delineated. The high potential zones correspond to the fracture valleys, valley fills, pediments and denudational slope, which coincide with the low slope and high lineaments density areas. The low zone mainly comprise structural hills and escarpments and these act as run-off zones. The derived panchayath-wise groundwater potentiality information could be used for effective identification of suitable locations for extraction of potable water for rural populations.