Processed bed elevation picks from airborne radar depth sounding across the Evans Ice Stream, Southern Palmer Land (1994/95 season)

The survey collected a total of 11,500 km of data along 22 lines, spaced 12 km apart and oriented perpendicular to the strike of both the Bouguer anomaly field, as derived from land data (McGibbon and Smith, 1991), and the major sub-ice topographical features (Doake et al., 1983). The speed of the aircraft was set to produce a sample spacing of about 60 m and the data were collected at heights between 1600 and 2000 m above sea level. The gravity signal was recorded using a LaCoste and Romberg air/sea gravimeter, S-83, which has been kindly loaned to BAS by the Hydrographic Office of the Royal Navy. The meter was modified by the ZLS company for use in an aircraft. The equipment was deployed in a BAS De-Havilland Twin Otter aircraft. Differential, dual frequency, carrier phase, GPS measurements of the aircraft's motion were made using Trimble and Ashtech geodetic receivers and antennas. Ice thickness data were obtained using a BAS-built, radio echo sounding system (Corr and Popple, 1994). Ice-bottom returns over most of the survey area were obtained at a sample spacing of approximately 28 m. GPS measurements were tied into base stations in International Terrain Reference Frame network (Dietrich et al., 1998) and gravity measurements to base stations in the IGSN71 net (Jones and Ferris, 1999). We present here the processed bed elevation picks from airborne radar depth sounding collected using the BAS PASIN radar system. Data are provided as XYZ ASCII line data.

本调查沿22条测线累计采集了11500千米的数据，测线间距为12千米，且测线走向垂直于由陆地数据推导得到的布格重力异常场（Bouguer anomaly，McGibbon与Smith, 1991）以及主要冰下地形特征（Doake等, 1983）的走向。飞机飞行速度经设置以实现约60米的采样间距，数据采集高度介于海拔1600至2000米之间。重力信号采用拉科斯特-隆伯格（LaCoste and Romberg）S-83型航空/海洋重力仪记录，该仪器由英国皇家海军水文局出借予英国南极调查局（British Antarctic Survey，简称BAS）。该重力仪经ZLS公司改装，以适配航空搭载场景。整套设备搭载于英国南极调查局的德哈维兰双水獭（De-Havilland Twin Otter）飞机上。飞机运动参数采用Trimble与Ashtech大地测量接收机及天线，通过差分双频载波相位GPS技术进行测量。冰厚数据采用英国南极调查局自研的无线电回声测深系统（radio echo sounding system）获取（Corr与Popple, 1994）。在绝大多数调查区域内，冰底回波信号的采样间距约为28米。GPS测量采用国际地形参考框架（International Terrain Reference Frame）网络中的基准站进行联测（Dietrich等, 1998），重力测量则依托国际重力基准网71（IGSN71）中的基准站完成联测（Jones与Ferris, 1999）。本文展示了采用英国南极调查局PASIN雷达系统采集的航空雷达测深数据所得到的经处理冰床高程采样点数据。数据以XYZ格式ASCII文本测线数据形式提供。