利用GPS进行切沟侵蚀监测研究

切沟侵蚀在土壤侵蚀中占据重要位置,切沟侵蚀监测研究是切沟侵蚀研究的重要方面。目前进行切沟侵蚀监测研究主要利用摄影测量的方法,该方法存在一定的局限性。对利用GPS进行切沟侵蚀监测研究进行了探讨,对切沟在不同时间进行测量,获得多个时相的DEM,通过对比不同时相的DEM来获取该时间段的切沟侵蚀变化。最后以位于黑龙江省漫川漫岗黑土区的丰产电流域的一条切沟为研究实例,建立了2002,2003年10月两个时段分辨率为0.4 m的DEM,对比这两个时段的数据表明,该切沟沟头后退达13.78 m,侵蚀面积增大了711m~2,切沟的土壤侵蚀量增加了2377 m~3,展示了GPS在切沟侵蚀研究中精度高、速度快等优越性,可为切沟侵蚀监测研究提供参考。     

水土流失定量监测中GPS实测更新GIS数据的实用方法研究

介绍了GPS实测更新GIS陈旧处数据的实用方法研究及其在水土流失定量监测中的应用。该方法由GPS软硬件接收设备组装的实测仪器、实施实测的要点、实测数据的投影系统转换与对GIS陈旧处数据的更新处理等部分组成。它在实测更新土地利用图的应用效果,与测绘界所采用的RTK技术方法比,更为经济、快速和实用,而其所定位置和更新的GIS数据结果在消除系统误差后则更为可信。它在实验研究区应用表明:利用原土地利用图和实测更新后的土地利用图所获得的水土流失定量监测的两个结果,后者的监测精度明显高于前者7个百分点;为提高监测水土流失和水质面源污染量的精度,必须重视实测、更新变化了的山丘土地利用界线。     

“3S”技术在水土保持工作中的应用及展望

随着遥感(RS)、地理信息系统(GIS)与全球定位系统(GPS)三项技术的飞速发展,其在水土保持工作中的应用也得到不断加强。基于“3S”技术在水土保持工作中的应用,提出了“3S”技术的集成构想,最后对“3S”技术在水土保持中的应用做了相应的展望。     

Distribution, habitat and biomass of Pittosporum undulatum, the most important woody plant invader in the Azores Archipelago

Pittosporum undulatum Ventenat (Pittosporaceae) is a tree or shrub native to Australia introduced in the Azores Islands in the 19th century, presently naturalized in the nine islands. According to a random survey of vascular plants in the Azores, the invader is present throughout the archipelago, in 62% of 547 1-km² samples. It was found in pure or mixed stands, forming groups and also as isolated trees. P. undulatum was frequently found in native scrubland (62%), mixed woodland (39%) and hedgerows (25%). The altitudinal range extended from sea level up to about 800 m a.s.l., with the highest frequency between 100 and 400 m. The woody species more strongly associated with P. undulatum included characteristic native and endemic species as well as non-indigenous and invasive taxa. Based on a forest inventory, 49% of the forested area in the Azores, about 24,000 ha, is occupied by P. undulatum. Considerable areas inside Island Natural Parks are covered by this species. The estimated annual P. undulatum biomass production in the Azores might range from only about 150 Mg in the small island of Corvo up to more than 60,000 Mg in Pico Island. The heating value of its wood and its chemical composition make it a good candidate for use in combustion or gasification processes. Since there are no resources available to control this large-scale invasion, using P. undulatum biomass for energy production might be an important factor to stimulate the progressive and sustainable cutting of its stands and its replacement by Macaronesian species.     

Comparison of Forest Inventory and Analysis surveys, basal area models, and fitting methods for the aspen forest type in Minnesota

The Forest Inventory and Analysis (FIA) unit of the U.S. Forest Service has collected, compiled, and made available plot data from three measurement periods (identified as 1977, 1990, and 2003, respectively) within Minnesota. Yet little if any research has compared the relative utility of these datasets for developing empirical yield models. This paper compares these and other subdatasets in the context of fitting a basal area (B) yield model to plot data from the aspen (Populus tremuloides Michx.) forest type. In addition, several models and fitting methods are compared for their applicability and stability over time. Results suggest that the three parent datasets, along with their subdatasets, provide very similar three parameter B yield model prediction capability, but as model complexity increases, variability in coefficient estimates increases between datasets. The absence of data for older aspen stands and the inherent noise within B data prevented the exact determination of an overall best model. However, the model B = b₁S^b₂(1 − exp( − b₃A)) with site index (S) and stand age (A) as predictors was found consistently among the highest in precision and stability. Additionally, nonlinear least squares and nonlinear mixed-effects fitting procedures produced similar model fits, but the latter is preferred for its potential to improve model projections. The results indicate little practical difference between datasets from different time periods and different sizes when used for fitting the models. Additionally, these results will likely extend to other states or regions with similar remeasurement data on aspen and other forest types, thus facilitating the development of other ecological models focused on forest management.     

用曲面拟合法确定平原区域正常高的方法

对应用GPS技术结合几何水准测量资料确定正常高的方法进行了研究,针对测区地形特点,选择合理的曲面拟合数学模型,并以此为基础建立计算其他GPS点高程异常和正常高的方程。同时,结合工程实践对上述求解方程进行了验证,其拟合结果的标准差为1.1cm,达到了四等水准测量的要求。研究证明,采用一定密度及合理分布的GPS水准高程联测点,选择曲面函数模型拟合区域大地水准面,是平原区域确定正常高的一种行之有效的方法。     

手持GPS测量面积的精度分析

介绍了手持GPS在森林资源调查、工程造林中林地面积测量的精度,选择已知面积作为测量对象,对测量误差及其精度进行分析计算,结果表明:手持GPS测量林地面积的精度能够满足林业中的应用要求.     

基于GPS模块的便携式农田面积测量仪

全球定位系统在精细农业中起着十分重要的作用,本文利用GPS的定位功能,研制了农田面积快速测量仪.测量仪由低成本的GPS模块、单片机数据采集板、键盘及LCD显示等组成.给出了GPS定位信息的获取技术,多边形农田面积的计算方法,测量仪软硬件的设计原理等.试验结果表明测量仪能够快速测量任意形状农田的面积,相对测量误差小于2%,并且农田面积愈大,测量的相对精度愈高.     

PTK在城市测量中的应用

RTK技术,是GPS测量技术与数据传输技术的结合,是GPS测量技术中的一个新突破.文章阐述了RTK的含义、系统的组成以及其在测量领域内的应用,并结合实际举例其在城市测量中的应用.     

景观破碎带GPSRTK监测理论、技术方法及空间模型

由于自然或人为作用形成的景观破碎带不仅影响景观的观赏价值 ,还会引起水土流失和破坏生物多样性 .因此 ,对城乡景观破碎带的定量监测不仅有学术意义 ,更有应用价值 .该项目通过对各类景观破碎带的GPSRTK技术定量监测建立各类景观破碎带的空间分布数学模型 ,并精确监测其地图 (投影 )面积、临空面积、土方体积及其变动 ,为治理景观破碎带提供基础信息 .