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.     

农村土地调查基本农田上图方法

土地是人类赖以生存和社会发展的物质基础,耕地是农业生产最基本、不可替代的生产资料。基本农田调查是农村土地调查最为重要的一个部分,基本农田上图工作对于政府部门制定土地政策、优化土地结构、保护耕地、提高耕地质量具有十分重要的意义。本文从基本农田概念的引入、基本农田上图技术流程、基本农田保护块上图以及图件编制、数据汇总几个方面阐述了农村土地调查基本农田的上图方法。     

测绘行业贯彻ISO9000族标准的若干思考

随着社会主义市场经济的日益完善和管理科学的不断发展,产品质量越来越引起各行各业的高度重视。为了促进测绘行业质量管理的科学化,程序化和标准化,逐步实现管理模式与国际接轨,提高测绘质量管理水平,增强市场竞争能力,在绘行业推行ISO9000族标准已势在必行。文中简要介绍了ISO9000族标准的基本概念,阐述了贯彻认证的意义,方法及步骤等。     

基于3维的基础测绘成果客户选图服务系统研究

探讨了GeoGlobe3维GIS技术在基础测绘成果客户选图服务中的应用,主要包括系统框架设计和具体功能。     

浅谈现代测绘技术装备在国土资源管理中的应用

进入新世纪以来,随着计算机技术、信息技术等新技术的发展,测绘技术装备也得到迅速发展,现代测绘技术装备在自动化、高效化方面的能力越来越突出,获取的数据类型也更加多样化。利用现代测绘技术装备服务于国土资源管理已经是大势所趋。本文结合现代测绘技术装备在国土资源管理中的应用范例,给出了相应建议,旨在提高现代测绘技术装备的应用能力,为国土资源管理提供全方位的服务。     

试析GIS技术在房产测绘中的作用

以GIS技术在房产测绘中的作用探索研究为题展开论述。首先,介绍了GIS技术操作简单、工作效率高、功能全面,可以实现全天候工作的优势特点。然后,结合测绘行业方面的相关经验,提出该技术在房产测绘中的作用。最后,对GIS技术的改进做了简单分析。希望可以提高GIS技术在房产测绘中的工作效率,促进我国房产事业的长期、稳定发展。     

鸡西市数字地籍测量实施方案研究

数字地籍测量是以计算机为平台,利用数字化设备采集野外数据,将数据存储在计算机里,利用数据处理软件和绘图软件生成地籍图、表册等地籍资料的一种自动化测绘技术。本文对地籍测量的内容与方法作了概述,主要阐述现代测量技术在地籍测量中的应用,对传统地籍测量技术和现代测量技术进行了比较,充分说明了现代测量技术的优越性;并对几种数字地籍测量模式进行了比较,针对不同要求的测量任务和不同环境的测区,应用不同的测量模式来完成任务,可提高测量效率和质量。     

RTK工程放样方法在大比例尺数字测图中的应用

结合工程实例,对在空旷平坦的地块进行大比例尺数字测图时,利用RTK技术进行细部地物测量,辅以工程放样的方法测量地形点,并对测图作业的方法进行了探讨。     

Early-season mapping of crops and cultural operations using very high spatial resolution Pléiades images

The aim of this study was to assess the contribution of very high spatial resolution (VHSR) Pléiades images to both early season crop identification and the mapping of bare soil surface characteristics due to cultural operations. The study region covering 21 km² is located west of the peri-urban territory of the Versailles plain and the Alluets plateau (Yvelines, France). About 100 cropped fields were observed on the ground synchronously with two Pléiades images of 3 and 24 April 2013 and one SPOT4 image of 2 April 2013. The GIS structuring of these field data along with vector information about field boundaries was used for delimitating both training and test zones for the support vector machine classifier with polynomial function kernel (pSVM). The pSVM was computed on the spectral bands and NDVI for both single-date Pléiades and the bi-temporal Pléiades pair. For the single-date classifications of crops, the overall per-pixel accuracy reached 87% for the SPOT4 image of 2 April (6 classes), 79% for the Pléiades image of 3 April (6 classes) and 82% for that of 24 April (7 classes). At the earlier date (2–3 April), the Pléiades image very well discriminated cultural operations (>77%, user’s or producer’s accuracies) as well as fallows and grasslands, while winter cereals and rapeseed were better discriminated by the SPOT4 image winter cereals (>70%, user’s or producer’s accuracies). As Pléiades images revealed within-field spatial variations of early phenological stages of winter cereals that could be critical for adjusting management of zones with delayed development during the growing season, they brought information complementary to multispectral images with high spatial resolution. For the bi-temporal Pléiades image, the overall per-pixel accuracy was about 80% (7 classes), winter crops, grasslands and fallows being very well detected while confusions occurred between spring barley at initial stages (2–3 leaves) and bare soils prepared for other spring crops. Using an additional validation field set covering ∼1/3 of the study area croplands, the crop map resulting from the bi-temporal Pléiades pair achieved correct crop prediction for about 89.7% of the validation fields when considering composite classes for winter cereals and for spring crops. Early-season Pléiades images therefore show a considerable potential for anticipating regional crop patterns and detecting soil tillage operations in spring.     

Attenuation of compressional waves in peridotite measured as a function of temperature at 200 MPa

A technique has been developed to determine attenuation in rocks at high temperature using a gas-media, high-pressure apparatus. A pulse transmission technique and a spectral ratio method are used to study compressional seismic properties of rocks. Seismic waves are transmitted to and from the sample through buffer rods of mullite. The effect of seismic wave reflections within the sample assembly are cancelled out by taking ratios of the spectra measured at different temperatures. In order to obtain good signal-to-noise ratio for resolving the attenuation at high pressure and temperature, special care is taken in the sample assembly and the ultrasonic coupling between the sample, buffer rods and transducers. A very tight connection of the sample-buffer rod-transducer is essential for obtaining high frequency signals (>300 kHz) at high temperature. A small mass is attached to each outside end of the transducer to drive low frequency signals (<250 kHz) into the sample. Before attenuation measurements, the sample and the buffer rods are tightly compacted in a platinum tube at high pressure and room temperature to ensure pressure seal of the sample assembly. The frequency range of measurement covers 50 to 450 kHz for the sample. Attenuation is very small in the buffer rod compared to the sample for the entire temperature range of the study. Because of the small attenuation, a wide frequency band of 50 kHz to 3.2 MHz can be covered for investigating the attenuation in the buffer rod. The technique has been used to measure attenuation at high confining pressure, and temperatures including sub- and hyper-solidus of upper mantle rocks. Therefore, effects of partial melting on attenuation can be studied.The method is applied to the attenuation measurement in a peridotite as a function of temperature to 1225°C at 200 MPa confining pressure. At high temperature, signal amplitude decays more rapidly at high frequency than at low frequency, from which attenuation (andQ) can be determined using a spectral ratio method. No frequency dependence ofQ is resolved for both the sample and the buffer rod over the entire temperature and frequency ranges of the measurement. The results show thatQ decreases rapidly with increasing temperature even in the temperature range below the solidus of peridotites. Such temperature sensitivity ofQ is probably more useful to probe thermal structure in the upper mantle than that of conductivity at temperatures below the solidus. The results in this study are compared with available seismic velocity, electrical conductivity and solidus data for peridotites, suggesting that there is no discontinuous change in both mechanical and electrical properties of peridotites at the solidus temperature. Even at hypersolidus temperatures, it appears that velocity drops and conductivity increases continuously (not abruptly) with increasing melt fraction. This implies that mechanical and electrical properties of the upper mantle will gradually change at the boundary where the geotherm crosses the solidus.