Going for gold with LiDAR

机载LiDAR是一种快速且相对便宜的方法，可以收集对采矿作业成功和安全至关重要的地形信息。加拿大卑诗省温哥华的McElhanney Consulting Services Ltd.已推出了针对采矿业的勘探和剥削阶段开发的两项新的裸露地图服务。在第一个应用中，麦克尔汉尼（McElhanney）使用激光雷达（LiDar）找到了由于茂密的营养覆盖而被空中摄影和卫星成像所遗漏的表面结构和谱系。工程，地图和测量公司McElhanney验证了不列颠哥伦比亚省金矿矿业区的LIDAR BARE-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-EAR-ERA-ERE-ERE-ERE-ERE-ERE-ERE-ERE-MAINGING模型（DEMS）。

表面谱系是与复杂地下地质结构相关的线性地面特征，包括断层，断裂和其他特征，例如不同岩石类型之间的接触。有时，只有半米宽，谱系可能会延伸数百米。由于它们的规模很大，这些功能可能很难从地面上发现，如果被植被或散落的沉积物掩盖，它们在大多数远程感知的图像中都可能很难看到。

“Lineaments provide clues to underground geology and are a valuable aid to geological mapping – a crucial part of any gold exploration or mine engineering project,” says Azadeh Koohzare, Ph.D., P.Eng. “Geologists can interpret the pattern and direction of these surface features and, as many gold deposits are associated with geological structures, use this information when selecting and prioritizing exploration targets.”

需要高点密度
The key to revealing the hidden surface geology is a powerful multipulse airborne laser scanner, or LiDAR, explains Koohzare. McElhanney, which owns three Leica Geosystems LiDAR scanners and two Leica Geosystems ADS digital cameras, initiated the lineament mapping project using the Leica ALS60 and is upgrading to the more powerful 500 kHz ALS70-HP system.

These LiDAR systems provide the minimum two points per square-meter (two points per 2.4 square yards) density required to generate bare-earth DEMs with an accuracy and resolution sufficient for revealing the narrow linear surface features. In the British Columbia pilot project, McElhanney operated the LiDAR at an altitude of 2,500 – 3,000 m (8,200 – 9,800 ft) above mean sea level to collect the data set. Standard processing removed the returns associated with vegetation to generate a bare-earth DEM with 10 cm (4 in) vertical and 30 to 50 cm (12 to 20 in) horizontal accuracy.

Koohzare说：“ Leica Geosystems ALS激光雷达以高脉搏速率运行，以确保植被以足以找到仅50 cm（20英寸）宽度的表面谱系的点密度渗透。”“该装置的高功率意味着可以以高飞机速度捕获密集的点数据，从而节省了时间和金钱。”

Ground Subsidence
麦克尔汉（McElhanney）设计了在萨斯喀彻温省（Saskatchewan）进行地面沉降监测的想法，在那里开采了钾肥并用于肥料。钾盐提取比许多其他类型的采矿构成了更高的地面沉积风险，因为在结构上不适合隧道的软岩层中发现了蒸发沉积物。结果，必须不断监测钾盐地雷，以使其上方和周围的地面沉降或下沉。

Koohzare说：“矿山上方的沉降提前警告说，内部人员可能有洞穴或倒塌的危险。”他补充说，沉降和抬高可能会导致从矿山朝任何方向朝任何方向造成5公里（3英里）的问题地点。除了矿山内部的危险外，地面运动还可以切断管道，损坏道路和在受影响地区的裂缝建筑基础。

Monitoring subsidence around potash mines – and other mineral extraction projects – is typically carried out using traditional ground survey techniques, which are expensive and time consuming. Based on LiDAR operations in hundreds of projects, many involving energy and mining clients, McElhanney says that airborne LiDAR is the fastest and most costeffective way to monitor ground subsidence.

从公司的Leica ALS60和ALS70激光扫描仪通常产生的裸露Dem的10厘米（4 in）垂直精度可以识别地面上的重大变化（无论是向上还是向下），这可能表明矿山中的危险条件。McElhanney建议收集每个矿场上方的初始基线数据集，然后每年继续收集新数据。一旦揭示了沉降，应在矿山内采取步骤以最大程度地减少危险时重复监视航班。

As is the case with the lineament mapping, the highpulse rate of the LiDAR sensor is crucial to penetrating the vegetative canopy around the mine site to get extremely accurate elevation measurements of the ground surface, or bare earth, according to Koohzare.

The Leica ALS70 is one of the few airborne laser scanners with the power and multi-pulse capability able to provide the quality of bare-earth DEM required for these mining applications.

Written by Kevin P. Corbley