RECOVER MAP 3.1.3.4 Landscape Pattern - Vegetation Mapping

The AHF system has been deployed in a series of survey campaigns to collect over 60,000 points covering Everglades National Park, Loxahatchee National Wildlife Refuge, Water Conservation Areas 2 and 3, portions of Big Cypress National Preserve, as well as areas along the Lake Okeechobee littoral zone. Since the AHF System is able to penetrate Everglades vegetation and water cover, it has provided an unprecedented regional view of Everglades topographic gradients and sub-water surface structure. These data are now being used to simulate Everglades water flow with higher resolution and greater accuracy, to estimate water depths in real-time for field study planning, and as input for habitat models used to forecast the effects of water level changes on various important species. The elevation data collected through this project also formed the basic input to generate a regional topographic surface that is the basis for the Everglades Depth Estimation Network (EDEN). These high accuracy elevation data are made available to anyone through the South Florida Information Access website (http://sofia.usgs.gov) data exchange pages. MAP Activity Accomplishment The USGS Airborne Height Finder (AHF) System was used to perform topographic surveys in Water Conservation Area 3A within the extents of the Lone Palm Head and North of Lone Palm Head 7.5-minute topographic map quadrangles as specified in the MAP/COE Interagency Agreement. The AHF system has been used throughout South Florida for elevation data collection because traditional surveying methods are too difficult, too costly, or simply impossible to use in the harsh wetland environment and broadly inaccessible terrain of the Florida Everglades. This is especially true considering the shear size of the hydrodynamic and biological modeling domains. The AHF is a helicopter-based instrument that uses a GPS receiver, a computer, and a mechanized plumb bob to make measurements. These data were post processed to the reference stations that are part of the AHF geodetic control network. For reasons of accuracy, these reference stations are located no more then 15 kilometers from the helicopter during AHF operations. The GPS data were post processed using Ashtech’s PNAV On The Fly (OTF) software to obtain the trajectory of the AHF platform. These results are then processed through an in-house software package that separates the actual survey points and results from the trajectory. The points are manually checked to ensure data accuracy and completeness. Digital elevation models (DEMs) were then generated from the elevation point data. Existing elevation data derived from LiDAR data for this area were replaced with AHF derived DEMs for reasons of vertical accuracy. The DEMs have been posted on the South Florida Information Access (SOFIA) website: http://sofia.usgs.gov/exchange/desmond/desmondelev.html.机载高度测量系统（Airborne Height Finder, AHF）已在一系列野外调查任务中部署，累计采集超6万个测点，覆盖大沼泽地国家公园、洛哈奇基国家野生动物保护区、第二及第三水资源保护区、大柏树国家保护区部分区域，以及奥基乔比湖沿岸带沿线区域。得益于AHF可穿透大沼泽地植被与水体覆盖层的特性，其首次实现了对大沼泽地地形梯度及水下结构的区域性全景观测。当前，这些数据正被用于开展更高分辨率、更高精度的大沼泽地水流模拟，为野外研究规划提供实时水深估算支持，同时作为栖息地模型的输入数据，用于预测水位变化对各类重要物种的影响。本项目采集的高程数据还作为基础输入，生成了区域性地形表面模型，该模型亦是大沼泽地水深估算网络（Everglades Depth Estimation Network, EDEN）的构建基础。上述高精度高程数据可通过南佛罗里达信息访问（South Florida Information Access, SOFIA）网站（http://sofia.usgs.gov）的数据交换页面向公众开放。 MAP项目成果 美国地质调查局（United States Geological Survey, USGS）机载高度测量系统（Airborne Height Finder, AHF）被用于在Lone Palm Head及Lone Palm Head以北7.5分幅地形图幅范围内的第三水资源保护区3A区开展地形测绘，该区域范围符合MAP/美国陆军工程兵团（Corps of Engineers, COE）跨机构协议中的规定。由于传统测绘方法在佛罗里达大沼泽地严苛的湿地环境与广泛难以通行的地形中实施难度大、成本高昂，甚至根本无法开展，因此AHF被广泛应用于南佛罗里达的高程数据采集工作，尤其是考虑到水动力与生物建模研究域的庞大规模。AHF是一款基于直升机平台的测量仪器，集成GPS接收机、计算机与自动化铅垂线装置开展测量。采集的数据经后处理，匹配至AHF大地控制网络中的参考站。为保障测量精度，AHF作业期间参考站与直升机的距离不得超过15公里。GPS数据通过阿施泰克（Ashtech）公司的PNAV实时动态（On The Fly, OTF）软件进行后处理，以获取AHF平台的飞行轨迹。随后通过内部自研软件对轨迹数据进行处理，分离出实际测绘测点与结果。所有测点均经过人工核查，以确保数据的准确性与完整性。随后基于高程测点数据生成数字高程模型（Digital Elevation Model, DEM）。由于垂直精度要求，该区域原有的激光雷达（LiDAR）数据衍生高程数据已被AHF生成的DEM所取代。上述DEM已发布至南佛罗里达信息访问（South Florida Information Access, SOFIA）网站：http://sofia.usgs.gov/exchange/desmond/desmondelev.html。