It can be common for some surveying team to capture 3D photogrammetry data in an extreme environment. From the top of the snow mountain to the hot desert, from the underground heritage to offshore oil platforms, our technicians and partners have been carrying their Civetta, I-detic, a DJI drone, or a simple DSLR camera these extreme environments to capture Virtual Reality tour and 3D models. In such a situation, the capturing team need to deal with some unusual challenges while ensure they fill the basic photogrammetry requirements. Each project our users and partners have done is unique, which also enabled us to explore our hardware solutions’ great potential. Therefore, it is time for us to go through five tips quickly we developed from experience.
1. Consider the limits of your team or your hardware
It is essential to check whether your 3D photogrammetry camera can operate in an extreme environment or not. For example, Civetta, the 230 megapixels HDR panorama camera, is recommended to perform between -10°C to 50°C temperature zone, with a humidity of 85% or less. The users or operation team can also contact the hardware provider to consult whether their hardware is suitable under some circumstances. Commonly, the camera’s battery life might be affected in an extreme temperature environment. Therefore, we usually recommend using an extra battery to support their 3D photogrammetry camera operation. To best deal with clients with special needs, Civetta can function in real-time while charging. Weiss AG can also provide customisation if clients require a larger internal battery for their Civetta. Our users reported that it is always challenging to find a place to recharge their device, as these rural areas or difficult to reach places are always the ones with a great demand for digitalisation. When a customer decided to purchase a 3D photogrammetry camera, all these details might not be clearly stated in their technical sheet or website. You can always search for case studies or 3D photogrammetry results to confirm its real adaptability.
An essential aspect to consider is human resources, such as how many staffs might need to participate in this project, their health status and the amount of work to be complete. Although it is difficult to forecast and plan when one does not have too much experience with photogrammetry capturing job, it is always possible to ask for advice from users using the same hardware. It is crucial to keep in mind that the 3D photogrammetry camera you have chosen can critically affect your work time and work quality. However, in other words, it also means that you can still calculate the amount of work for your project based on the operability of your camera. Therefore, you will need to know the minimum accuracy you would like to achieve for your project, as it will determine how closely you align with each photo. A general photogrammetry theory, the more valid photos we used as an input, the more accurate the model could be(yet each camera has its limit, so choosing a good camera is important). For example, the Civetta can automatically capture one HDR panorama image(360*180°) within 40 seconds, and you can calculate the time of setting up the camera or moving in-between spots. Thus you can figure out how much time you or your team would need to complete the entire project.
Another core consideration for human resources is how challenging your environment is and how can it negatively affect one’s performance. For example, many of our users had the experience of walking(or climbing) in the desert while carrying the Civetta, tripod, computer and many other pieces of equipment. It is common for them to work for long hours in the desert without access to the Internet, store or charging station. The natural environment and physical limitation can be the major factor that affects the actual capturing time, and some might not include these when planning the capturing time. One of our clients once uses the Civetta to capture an underground heritage in a wet and dark condition. To avoid the reflective surface caused by the wetness, they carefully choose a specific time frame for operation.
Finding a good combination of hardware and human resources is significant for you to operate in an extreme environment successfully, not just for efficiency but also for safety consideration.
2. Avoid the avoidable issues in photogrammetry
The photogrammetry technique has its strength and limitation. For example, it can capture accurate(real vector) colour point clouds with surface and texture information, which can never be achieved by a laser scanner. Yet, you might also need to be aware that the photogrammetry method has difficulties in processing images of an object with pure black or white, reflective or transparent surfaces. It could also bring great challenges for those who want to capture 3D models on top of a snow mountain(yet our technical team has achieved it before in a temple digitalisation project!) Therefore, you might need to find ways to overcome some of these limitations in photogrammetry, such as using a spray(not appliable in many situations), sticker, calibration tags or any label to help your computer algorithm recognise the object.
Given the environment you observed, one might use some supportive tools to enable a better-capturing experience and quality. For example, you might need to use some extra lighting for the underground. In such a case, one might need to revise its 3D photogrammetry capturing procedures again to avoid making mistakes — do not move the light; otherwise, the 3D model can never be formed. One might also want to consider using other tools, such as a tripod or even a robot.
3. Prevent data loss and cover all spots
It will be a nightmare if one found out their data are all gone due to human errors. Set up a straightforward procedure and make sure you have all the data transferred quickly to another device or hard drive after a certain period. Users can simply plug in their Civetta with their laptop with a USB 3.0 provided and transfer all the images captured within minutes. The capturing team can also choose to upload their raw image assets into a cloud, like the Visual Asset Management System VAM2. It allows the data processing team to start work with the data simultaneously with the capturing group. Thus, a processed 3D coloured point cloud or mesh can be uploaded and viewed directly on a web browser by clients or third parties.
It is common that you will only have one chance to capture data for your project in these extreme environments, as these are difficult to reach, require additional approval, costly, or simply cannot access without the client’s or institution’s permissions. Therefore, it is always essential to have a quick walk-through of the environment and understand the scene or building for capturing before planning. If you are not permitted to access the given region, you can ask the local staffs or department to send you some photographs, maps or CAD for you to use as a reference for planning. When selecting the capturing spot, try to choose a stable position to avoid shaking, which can cause errors in the data captured.
Although photogrammetry enables you to re-capture the missing part for processing, the best way to avoid doing it is to plan carefully and choose all the capturing spots before the capturing process. For instance, we recommend our user to set up each Civetta capturing spot 5-10 meters away from each other while making sure the new spot can see the old capturing spot with human eyes. Given this rule, it becomes much easier to set up the plan and avoid missing data, even for those who have no experience in photogrammetry.
Lastly, organising your captured data is a critical aspect to consider, especially in a large-scale project. Sorting, grouping and labelling your data and other assets can directly affect the quality of the digital twins.
4. Consider a combination of methods
In some cases, you might need to consider using a combination of methods to capture data for 3D reconstruction. A Civetta itself usually produce a very high-quality 3D result. Yet, if you might want greater accuracy for a particular area or object, you might want to use the Civetta with I-Detic, DSLR, lidar, laser or other devices. The drone is also considered a good option as it helps the 3D reconstruction algorithm better recognise each panorama image’s relationships. Commonly, you might need people(or team) from different specialities to operate these devices. Good communication and a clear plan are always the core for a multidisciplinary team.
Suppose one would like to better manage all different sources of data they collected for the scene. In that case, they might want to consider using the Visual Asset Management VAM2 system to store the captured data and showcase the post-processing result. Notes that the VAM2 enables you to showcase and manage all types of assets via a single web-browser. You can still benefit from VAM2 if you have no access to the Internet. The VAM2 provide a stand-alone version specifically for users who have no Internet access or have high-security requirements.
5. Clear communication with the local staffs or responsible person
Local staffs are usually the only support one could get when capturing data in an extreme environment. They are experienced, familiar with the environment, and know what to do to make your work easier. It is important to have someone in the team clearly explain what one expected to do during the entire capturing process, how long it will take and what you would like to avoid. No one wants any surprises in an extreme environment, same for the local staffs. In some circumstances, one might even need to make sure their staffs are trained with safety instruction.
Feel free to let us know your thoughts about this topic. What are your tips for 3D photogrammetry data capturing in an extreme environment?
Author: Christiane Zhao