Topographic measurements of Little Holland Tract, Sacramento-San Joaquin Delta, California, 2015, using backpack GPS

Topographic data were collected by the U.S. Geological Survey (USGS) in 2015 for Little Holland Tract in the Sacramento-San Joaquin River Delta, California. The data were collected on foot using a global positioning system (GPS) backpack platform that consisted of survey-grade Trimble R10 and R7 global navigation satellite system (GNSS) receivers with Zephyr 2 antennas. Orthometric elevations relative to NAVD88 were computed using the National Geodetic Survey Geoid12a, and the final data were projected in Cartesian coordinates using the UTM Zone 10 North (meters) (NAD83[2011]) coordinate system. The mean estimated vertical uncertainty of the 2015 USGS GPS backpack survey is 3.5 cm.本数据集的地形数据由美国地质调查局（U.S. Geological Survey, USGS）于2015年针对加利福尼亚州萨克拉门托-圣华金河三角洲的小荷兰地块（Little Holland Tract）采集。数据采用背负式全球定位系统（GPS）平台徒步采集，该平台搭载测量级天宝R10（Trimble R10）与R7（Trimble R7）全球导航卫星系统（GNSS）接收机及Zephyr 2天线。以北美垂直基准面1988（NAVD88）为基准的正高通过国家大地测量局Geoid12a（National Geodetic Survey Geoid12a）计算得到，最终数据采用通用横轴墨卡托投影第10北纬带（米制，NAD83[2011]）笛卡尔坐标系进行投影。2015年USGS背负式GPS测量的平均估算垂直不确定度为3.5厘米。