Ground conductivity measurements at selected National Wildlife Refuges, Montana and North Dakota, 2017-2018

Shallow subsurface electrical conductivity was mapped at selected U.S. Fish and Wildlife Service managed lands in northeast Montana and northwest North Dakota using the DUALEM421 electromagnetic sensor (Dualem, Inc., ON, Canada) in the winters of 2017 and 2018. Data were acquired by towing the DUALEM421 sensor on a sled behind an all-terrain vehicle or snow machine, with the sensor at a nominal height of 0.3 meters (m) above ground surface. Approximately 427 line-kilometers (km) of data were acquired over an area of nearly 26 square-kilometers. Data were manually edited to remove sensor dropouts, lag corrected for apparent offsets between recorded GPS location and data locations for each coil pair, and averaged to a sounding distance of 1m along the survey path; data were not decoupled from infrastructure noise sources (powerlines, pipelines, fences, etc.) or corrected for sensor pitch or roll. This data release contains raw and processed electromagnetic data. Digital data are described by the data dictionaries. Additional details regarding the processing steps are described in the metadata.

2017年与2018年冬季，研究人员使用DUALEM421型电磁传感器（加拿大安大略省Dualem公司），对美国鱼类及野生动物管理局（U.S. Fish and Wildlife Service）管辖的、位于蒙大拿州东北部与北达科他州西北部的指定地块，开展了浅层地下电导率填图工作。
数据采集时，将DUALEM421传感器安装于雪橇之上，由全地形车或雪地摩托牵引，传感器距地面的标称高度为0.3米（m）。本次作业覆盖近26平方千米的区域，累计获取约427测线千米的有效数据。
采集得到的原始数据经如下处理：人工剔除传感器信号中断的无效记录；针对每个线圈对的记录GPS位置与对应数据位置间的表观偏移进行滞后校正；沿测线路径将数据平均至1米的测深间距。本数据集未对输电线、管道、围栏等基础设施噪声源进行去耦处理，也未校正传感器的俯仰与横滚误差。
本数据发布包包含原始电磁数据与经处理的电磁数据，数字数据的详细说明可通过数据字典查阅；有关数据处理步骤的更多细节，可参阅元数据（metadata）。