IntroĀ
You can make use of the iPad's built in LiDAR sensor (2020, 2021, 2022 & 2024 iPad Pro) to generate a 3D scan of a rock face or wall that can complement or replace the rock face photograph. The LiDAR scan is captured either as a 3D coloured point cloud OR 3D textured mesh (recommended) and can be georeferenced right within the app.Āā¹ļøĀ The rock face photograph and the 3D LiDAR scan share the georeferencing information such as face heading, distance to face and laser station. You will need to pick the same reference point on both the photograph and the LiDAR scan. Read Step 3: Georeferencing for more details.
We recommend to capture both a photograph and a 3D LiDAR scan (choose Scan Mesh) for each rock face.
āĀ Before starting a LiDAR scan please consider that:
- LiDAR in Rock MapperĀ only works in illuminated areas. Besides the LiDAR sensor (that uses a near infrared laser), the camera(s) on the iPad Pro are used to simultaneously capture colour information which is only possible if the area of interest is illuminated. We recommend to use our Dual LED light array that is included in the Rock Mapper Hardware Kit.Ā
- Apple's officialĀ range rating for the LiDAR sensor is 5m. By walking and moving the iPad you can scan much larger areas such as walls. However, it is not possible to generate scans of a large/tall stopes or within unsupported areas that you cannot get within 5m. In such cases you can still take a still picture with Rock Mapper or you could consider solutions suchĀ HoverMapĀ orĀ Geoslam.Ā
- For practicality reasons, Rock Mapper automatically stops each scan at a certain point or mesh triangle limit to keep files at a practical size (see progress bar in lower left corner while scanning). Even with this limit, you can easily generate a LiDAR scan of aĀ rock face (including backs and walls) or scan a wall that's 25m long. If you want to capture larger areas, then always choose the Scan Mesh option instead of Scan Point Cloud and/or capture the area of interest in individual/separate scans and later merge them usingĀ CloudCompareĀ or 3rd party laser scanning software such as Maptek's PointStudio.
- The LiDAR sensor used in the iPad Pro isĀ not survey gradeĀ and is not intended to replace a fully fledged laser scanner system (that costs AUD 100k+). Nevertheless, Rock Mapper's 3D Scan | LiDAR feature is a very quick, setup- and hassle free way of capturing rock faces as 3D models that are fit-for-purpose when it comes toĀ geological mapping & sampling. Moreover, the app makes sure to keep scan file sizes manageableĀ and therefore allowing to routinely collect these data (operational geology).Ā Ā
ā¹ļøĀ LiDAR Scanning is performed in real-time on the device without the need of a tripod as it is the case for traditional laser scanning setups. It only takes 15-45 seconds to scan a whole face including backs and walls.Ā All 3D processing and georeferencing is done right within the app and only takes seconds. The coloured 3D point cloud OR photorealistic 3D model is included in the Rock Face ZIP file.
Workflow
š Start new LiDAR scan
We recommend to use the LiDAR > Scan Mesh option.Ā Ā
ā¹ļøĀ Please note that LiDAR scanning requires the face/wall to be illuminated. We recommend the use a powerful LED light or our custom-designed Dual LED light array which is part of the Rock Mapper Hardware Kit.
Position yourself about 1-5m in front of the rock face/rock wall and then press the round trigger button. Hold the iPad still for 1-2 seconds until the LiDAR sensor has initialised and the scan starts to appear in the live view.Ā
ā¹ļøĀ Change your position and slowly move the tablet up and down in order to capture all areas as if you were using a spray can and trying to apply paint to a wall. Try to avoid scanning the same area twice and avoid any jerky movements.Ā
The 3D data is rendered on the screen in real-time as the scan progresses. In the lower left corner you can see information about scan size limit. The scan will automatically stop when that threshold is reached, but you can stop the scan earlier by pressing the stop/shutter button.
ā¹ļøĀ The estimated point number includes also points with low level confidence. Rock Mapper only stores and uploads points that have a high level of confidence. Therefore the final point cloud will have less than 3.5 Million points (= max point limit).
After stopping the LiDAR Point Cloud scan, it will be automatically loaded into the 3D View and is available within a split second. It can then be rotated (1 finger), zoomed in/out (pinch-to-zoom) and panned (2 fingers).
LiDAR mesh scans will require an on-device processing step to compute the final texture. We recommend to choose Standard Quality to avoid any memory related stability issues because it's a computationally expensive step.Ā
In case the project already has a georeferenced face photograph, reference information such as face heading, distance to laser station and laser station ID are automatically inherited because these information are shared between the face photograph and the LiDAR scan. However, you need to also pick the shared reference point on the LiDAR scan and rotate the scan to that it aligns with the face heading, which is described inĀ Step 3: Georeferencing.
ā¹ļøĀ It is possible to generate a Rock Face File that only includes a (georeferenced) 3D LiDAR scan. However, we recommend to always capture a rock face photograph as well because it's very quick to do so in Rock Mapper.