Mapping Stream Habitats with a Global Positioning System: Accuracy,Precision, and Comparison with Traditional Methods

We tested the precision and accuracy of the Trimble GeoXT™ global positioning system (GPS) handheld receiver on point and area features and compared estimates of stream habitat dimensions (e.g., lengths and areas of riffles and pools) that were made in three different Oklahoma streams using the GPS receiver and a tape measure. The precision of differentially corrected GPS (DGPS) points was not affected by the number of GPS position fixes (i.e., geographic location estimates) averaged per DGPS point. Horizontal error of points ranged from 0.03 to 2.77 m and did not differ with the number of position fixes per point. The error of area measurements ranged from 0.1% to 110.1% but decreased as the area increased. Again, error was independent of the number of position fixes averaged per polygon corner. The estimates of habitat lengths, widths, and areas did not differ when measured using two methods of data collection (GPS and a tape measure), nor did the differences among methods change at three stream sites with contrasting morphologies. Measuring features with a GPS receiver was up to 3.3 times faster on average than using a tape measure, although signal interference from high streambanks or overhanging vegetation occasionally limited satellite signal availability and prolonged measurements with a GPS receiver. There were also no differences in precision of habitat dimensions when mapped using a continuous versus a position fix average GPS data collection method. Despite there being some disadvantages to using the GPS in stream habitat studies, measuring stream habitats with a GPS resulted in spatially referenced data that allowed the assessment of relative habitat position and changes in habitats over time, and was often faster than using a tape measure. For most spatial scales of interest, the precision and accuracy of DGPS data are adequate and have logistical advantages when compared to traditional methods of measurement.     

GPS车辆行驶记录定位监控信息管理系统

利用GPS,GIS和GSM等技术,试验开发"GPS车辆行驶记录定位监控信息管理系统"。该系统由GPS定位系统、GPRS/CDMA移动通讯网络、Internet、监控中心组成。对装有车载终端的车辆进行行驶状态的数据采集,通过处理存储到数据库中,为管理人员查阅分析车辆当前状态提供数据。应用信息管理系统后,管理人员能及时了解掌握车辆的方位和状况,提高了生产和安全管理的效率,杜绝了跑私车、绕路行车等现象,有着较好的经济效益。由于信息系统的全天候、全方位监控车辆功能,为应对车辆行驶的安全突发事件的救助和决策提供了有效的手段,具有较好的安全运行效率、社会效益以及广泛的推广应用前景。     

汶川地震孕震机理的研究及其对地震预报的启示

2008年5月12日汶川8.0级大地震突发在现今并不活动的龙门山断裂带上,引起社会及学术界的巨大反响,该地震的孕震机理及如何预报问题更引起广泛关注.本文试图从纵横两个侧面来研究汶川地震发生的机理,即:先利用GPS资料研究地表的变形场,然后运用数值方法对横跨龙门山断裂带的一个剖面进行模拟.文中的计算结果显示:①汶川地震前龙门山断裂带及附近地区地表的主应变率的方位与该区域的地应力方位基本一致,但形变量值很小,表明断层处于闭锁之中;②对地震发生过程进行有限元模拟的结果,显示等效应力及变形能量密度在空间分布由分散状态逐步向龙门山地区集聚,龙门山断裂带上地震复发周期约为3 163年.因此,根据前人的研究结果及本文的研究认为汶川大地震的动力成因可能为:随着印度洋板块对欧亚大陆的不断挤压碰撞,青藏高原隆升后形成的物质东流在向东运动过程中由于受到稳定的四川盆地的阻挡,一部分东流物质在川西地区囤积,造成龙门山隆升;高角度、铲状的龙门山断层面上的正应力随着川西高原的向东运动而不断增大,再加上断层附近介质刚性大,这就导致该断层的闭锁程度增高;但另一方面随着高原东流物质的不断向东运动,龙门山下部地壳囤积的东流物质不断地向斜上方推挤龙门山断层上盘,这样会导致龙门山断裂带上的剪应力越来越大;当剪应力超过摩擦强度时,断层解锁发生地震.最后,针对这种发震机理的新型地震,提出了今后关于地震预报的几点思考.     

上海环保热线车辆指挥调度系统建设方案

为了强化环保部门的执法力度，上海市设计和建立了一个以GIS、GPS技术为核心的车辆指挥调度计算机系统。文章概述了GIS、GPS的基本特点，介绍了整个车辆指挥调度系统，包括其流程、软硬件等。通过车辆指挥调度系统可以接受GPS数据、在地图上显示车辆位置、处理GPS错误信号、按条件调度车辆，以便及时处理环境保护应急事件。     

连续纵向水质监测方法在温瑞塘河的应用

水质监测结果是水质评价与水污染防治的重要依据。针对常规定点水质监测方法无法完整再现水质指标的时空连续分布特征的问题,将船只搭载的水质实时监测设备与GPS同步形成基于GIS数据支撑的连续纵向水质监测方法。重点对水质监测仪及GPS空间数据集成问题进行了分析讨论,并在温瑞塘河流域进行了实验论证。结果表明,连续性纵向水质监测不但能进行连续时空水质监测,还能与GPS、GIS结合进行连续性时空分布特征的分析。     

遥感技术在环境保护中的应用

当前，信息化工程在蓬勃兴起，数字化浪潮－浪高过一浪，数字地球，数学海洋，数字国土工程，数字环保，数字辽宁成为我们经常讨论的议题，在一般工一过程中的数显技术，数控技术，数字网络等概念更是家喻户晓，数字化是21世纪的标志。     

GPS在管线控制测量中的应用

对静态GPS在管线控制测量中的应用做了阐述,包括选点、数据采集和数据处理,结合GPS自带的后处理软件,以实例介绍了在数据处理中遇到的问题和解决方法.     

Taxi driver speeding: Who,when, where and how? A comparative study between Shanghai and New York City

Objective: The 3 objectives of this study are to (1) identify the driving style characteristics of taxi drivers in Shanghai and New York City (NYC) using taxi Global Positioning System (GPS) data and make a comparative analysis; (2) explore the influence of different driving style characteristics on the frequency of speeding (who and how?) and (3) explore the influence of driving style characteristics, road attributes, and environmental factors on the speeding rate (when, where, and how?)

Methods: This study proposes a driver–road–environment identification (DREI) method to investigate the determinant factors of taxi speeding violations. Driving style characteristics, together with road and environment variables, were obtained based on the GPS data and auxiliary spatiotemporal data in Shanghai and NYC.

Results: The daily working hours of taxi drivers in Shanghai (18.6 h) was far more than in NYC (8.5 h). The average occupancy speed of taxi drivers in Shanghai (21.3 km/h) was similar to that of NYC (20.3 km/h). Speeders in both cities had shorter working hours and longer daily driving distance than other taxi drivers, though their daily income was similar. Speeding drivers routinely took long-distance trips (>10 km) and preferred relatively faster routes. Length of segments (1.0–1.5 km) and good traffic condition were associated with high speeding rates, whereas central business district area and secondary road were associated with low speeding rates. Moreover, many speeding violations were identified between 4:00 a.m. and 7:00 a.m. in both Shanghai and NYC and the worst period was between 5:00 a.m. and 6:00 a.m. in both cities.

Conclusions: Characteristics of drivers, road attributes, and environment variables should be considered together when studying driver speeding behavior. Findings of this study may assist in stipulating relevant laws and regulations such as stricter offense monitoring in the early morning, long segment supervision, shift rule regulation, and working hour restriction to mitigate the risk of potential crashes.     

垃圾运输车智能监控管理系统

本产品是为解决垃圾运输车随意倾倒问题而开发的 ,它是一种新型智能化监控管理系统。它采用安装在运输车上的GPS接收机定位、测时 ,由车载车辆行迹记录仪数字化记录装载、运输、卸载的地点、时间等信息。经定期处理 ,完整、准确地反映出运输车工作过程 ,为管理部门对违规卸载车辆的科学取证提供了很好手段     

基于“3S”的红树林资源调查方法研究

论文研究了“3S”技术与地面调查相结合进行红树林资源调查的技术方法。以SPOT和Landsat7ETM+为信息源,经预处理后在GIS支持下进行目视判读和编制工作手图,实地采用GPS实测和目测勾绘修正小班界线,进入林内调查林况因子。结果表明,群落类型调查精度为100%;小班面积平均误差、小班周界平均位移、小班中心位置平均相对位移分别为11.8%、18.3m、13.1%,远小于常规方法(1∶10000地形图目测勾绘)的76.6%、108.7m和274.9%;效率比GPS实测高2.04倍,有效地解决了传统方法调查中存在的红树林空间位置和分布境界线定位准确性差、面积精度低,一般航天遥感调查分类精度低和GPS方法效率低等问题。