分析对比了多种地理空间定位方法，归纳了各种不同尺度下定位的特点，以及定位方法的实现过程，从IEEE802.11无线局域网技术的 MAC 协议出发，提出了基于无线局域网 IEEE802.11技术的地理空间定位方法，实现的技术流程，并分析了其发展...分析对比了多种地理空间定位方法，归纳了各种不同尺度下定位的特点，以及定位方法的实现过程，从IEEE802.11无线局域网技术的 MAC 协议出发，提出了基于无线局域网 IEEE802.11技术的地理空间定位方法，实现的技术流程，并分析了其发展趋势。利用 MAC 的帧头和帧体都可以实现定位功能，利用 MAC 帧头的定位可以适用于计算能力较强的移动台上，而利用帧体的定位，由于只需解析内容不需要查询计算，所以能够用于手机等移动对象。使用无线局域网可以实现定位平台，同时又能实现无线接入的通信功能，所以大大降低了总的建设成本，因此具有很大的现实意义。展开更多
Mapping the spatial distribution of soil nitrate-nitrogen （NO3=N） is important to guide nitrogen application as well as to assess environmental risk of NO3-N leaching into the groundwater. We employed univariate and...Mapping the spatial distribution of soil nitrate-nitrogen （NO3=N） is important to guide nitrogen application as well as to assess environmental risk of NO3-N leaching into the groundwater. We employed univariate and hybrid geostatistical methods to map the spatial distribution of soil NO3-N across a landscape in northeast Florida. Soil samples were collected from four depth increments （0-30, 30-60, 60-120 and 120-180 cm） from 147 sampling locations identified using a stratified random and nested sampling design based on soil, land use and elevation strata. Soil NO3-N distributions in the top two layers were spatially autocorrelated and mapped using lognormal kriging. Environmental correlation models for NO3-N prediction were derived using linear and non-linear regression methods, and employed to develop NO3-N trend maps. Land use and its related variables derived from satellite imagery were identified as important variables to predict NO3-N using environmental correlation models. While lognormal kriging produced smoothly varying maps, trend maps derived from environmental correlation models generated spatially heterogeneous maps. Trend maps were combined with ordinary kriging predictions of trend model residuals to develop regression kriging prediction maps, which gave the best NO3-N predictions. As land use and remotely sensed data are readily available and have much finer spatial resolution compared to field sampled soils, our findings suggested the efficacy of environmental correlation models based on land use and remotely sensed data for landscape scale mapping of soil NO3-N. The methodologies implemented are transferable for mapping of soil NO3-N in other landscapes.展开更多
文摘分析对比了多种地理空间定位方法，归纳了各种不同尺度下定位的特点，以及定位方法的实现过程，从IEEE802.11无线局域网技术的 MAC 协议出发，提出了基于无线局域网 IEEE802.11技术的地理空间定位方法，实现的技术流程，并分析了其发展趋势。利用 MAC 的帧头和帧体都可以实现定位功能，利用 MAC 帧头的定位可以适用于计算能力较强的移动台上，而利用帧体的定位，由于只需解析内容不需要查询计算，所以能够用于手机等移动对象。使用无线局域网可以实现定位平台，同时又能实现无线接入的通信功能，所以大大降低了总的建设成本，因此具有很大的现实意义。
基金Project supported by the United States Department of Agriculture through the "Nutrient Science for Improved Watershed Management" program (No.2002-00501)
文摘Mapping the spatial distribution of soil nitrate-nitrogen （NO3=N） is important to guide nitrogen application as well as to assess environmental risk of NO3-N leaching into the groundwater. We employed univariate and hybrid geostatistical methods to map the spatial distribution of soil NO3-N across a landscape in northeast Florida. Soil samples were collected from four depth increments （0-30, 30-60, 60-120 and 120-180 cm） from 147 sampling locations identified using a stratified random and nested sampling design based on soil, land use and elevation strata. Soil NO3-N distributions in the top two layers were spatially autocorrelated and mapped using lognormal kriging. Environmental correlation models for NO3-N prediction were derived using linear and non-linear regression methods, and employed to develop NO3-N trend maps. Land use and its related variables derived from satellite imagery were identified as important variables to predict NO3-N using environmental correlation models. While lognormal kriging produced smoothly varying maps, trend maps derived from environmental correlation models generated spatially heterogeneous maps. Trend maps were combined with ordinary kriging predictions of trend model residuals to develop regression kriging prediction maps, which gave the best NO3-N predictions. As land use and remotely sensed data are readily available and have much finer spatial resolution compared to field sampled soils, our findings suggested the efficacy of environmental correlation models based on land use and remotely sensed data for landscape scale mapping of soil NO3-N. The methodologies implemented are transferable for mapping of soil NO3-N in other landscapes.
