Laser Airborne Depth Sounder (LADS) bathymetry data (Australian Hydrographic Office)

LADS is a swath sounding system that collects data in a grid 240 metre wide, with a sounding at approximately every 10 - 11 metres. During normal survey operations parallel LADS survey runs are flown at 200 metre intervals, resulting in a 40 metre overlap between runs. A LADS survey run will have 24 columns of sounding data, of which 22 are useable. The soundings in columns 1 and 24 are not used for hydrographic purposes. Data along a LADS run is divided up into "FRAMES". One frame equates to two seconds of LADS data, an area 240 metres wide and 150 metres long. Each row or swath of soundings within a frame is known as a "SCAN". There are 14 scans to a frame. Thus a frame can contain up to a theoretical maximum of 336 soundings (pulses of the laser) in 24 columns and 14 scans (14 x 24 = 336). However as soundings in columns 1 and 24 are not used, therefore the total number of soundings in a frame is 308. Consecutive frames of data do not overlap. The centre of each frame has a GPS position applied to it. All other soundings within that frame will have their position calculated from the central position of the frame. Each frame also has a frame correction; corresponding to the tidal reduction, which is applied to all soundings within that frame.LADS survey runs are typically planned to be around 45 nm in length, although this can be varied. A run of this length will typically contain 550 frames of useable data or 169400 possible soundings. On a typical LADS sortie with 4.5 hours on task it is possible to fly 10 of these runs, as well as conduct a navigation calibration and fly a benchmark run. This equates to approximately 1.69 million possible soundings or an area surveyed of 52 sq nm. The largest area ever surveyed in a single sortie was 88 Sqnm. The area surveyed per sortie increases marginallyif the run lengths are increased but decreases drastically as run lengths are decreased, due to the lost time in turning between lines. Raw LADS data collected in the air is stored in binary form on Magneto Optical Disks. On returning to the ground the data is copied onto a single DAT tape, and is then automatically processed using the Ground Analysis Sub System (GASS) into a recognisable form.The available data covers the following survey areas:HI185: Flinders PassageHI193: Bunker Reef to Fairway ChannelHI220: Cooks Passage to Trinity OpeningHI221: Cape Weymouth to Blackwood ChannelHI221_2: Fairway Channel (NW Extension)HI241: Hope Island to Lark Pass© Commonwealth of Australia (Australian Hydrographic Office).

LADS是一种条带测深系统，以240米宽的网格形式采集数据，测点间距约为10~11米。在常规测量作业中，平行布设的LADS测线间隔为200米，测线间存在40米的重叠区域。单条LADS测线包含24列测深数据，其中22列为有效数据，第1列与第24列的测深数据不应用于水文测量用途。
LADS测线的数据按“帧（FRAMES）”进行划分：一帧对应2秒的LADS采集数据，覆盖宽度240米、长度150米的测量区域。一帧内的每一行测深条带被称为“扫描线（SCAN）”，单帧包含14条扫描线。因此理论上单帧最多可容纳336个激光脉冲测深点（24列×14条扫描线=336）。但由于第1、24列测深数据弃用，单帧有效测深点数量实际为308个。连续帧之间无数据重叠。
每一帧的中心点会被赋予GPS定位信息，该帧内其余所有测深点的位置均基于该帧中心点位置计算得到。每一帧还附带帧校正参数，对应潮汐改正量，将应用于该帧内的全部测深数据。
LADS测线通常规划为约45海里的长度，该参数可根据需求调整。单条该长度的测线通常包含550帧有效数据，对应最多169400个测深点。典型的LADS作业架次单次任务时长为4.5小时，可完成10条测线作业，同时可开展导航校准及基准测线飞行。该作业规模相当于最多可获取169万个测深点，或完成52平方海里的测量作业。单次架次的最大测量记录为88平方海里。当测线长度增加时，单架次测量面积会小幅提升；但由于测线间转向耗时增加，测线长度缩短时单架次测量面积会显著下降。
机载原始LADS数据以二进制格式存储于磁光盘（Magneto Optical Disks）上。返回地面后，数据会被拷贝至单盘DAT磁带，随后通过地面分析子系统（Ground Analysis Sub System, GASS）自动处理为可识别的标准格式。
本次可用数据覆盖以下测量区域：
HI185：弗林德斯水道
HI193：邦克礁至航道水道
HI220：库克水道至三一海峡入口
HI221：韦茅斯角至布莱克伍德水道
HI221_2：航道水道（西北延伸段）
HI241：霍普岛至拉克水道
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