The Reality Capture Journey - Part 2

Nearly 4500 scans and 155 points surveyed across 9 levels to cover close to 500,000 sqft of a densely packed central utility plant. That gives you an idea of what we were dealing with!

Welcome to Part 2 of the Reality Capture Journey Series. In this article, I’ll dive deep into the laser scanning process of this massive facility and describe our survey strategy, along with the challenges we faced onsite. If you missed Part 1, you can read it here. You’ll get the inside scoop of the scope of work and schedule, and learn about how we blindly estimated this project.

With no further ado, let’s jump right into it!

The stakeholders

As you might imagine, coordinating a project of this magnitude cannot be accomplished in a short period of time. It requires extensive planning, constant communication, and careful management of expectations for all parties involved. When it comes to site work, understanding and managing stakeholders is crucial to align project goals and mitigate risks since every delay in the project impacts the budget directly. In this project, our stakeholders included:

• Our client: an engineering firm.
• Our client’s client: the building owner and end user of the data we were about to capture.
• The on-site contact: the crew who would shadow our technicians during their entire stay onsite.
• The scanning crew: our partners, the laser scanning and survey crew.
• The point cloud users: our team, the BIM modelers.

In this complex environment, our role required us to navigate the interactions and juggle between all these players and our main responsibilities involved: understanding the client's goals, communicating them to our scanning partners, coordinating their work with our site contact to minimize disruptions, and ensuring they understood and collected the necessary data for our BIM team.

The scanning coordination:

What needs to get coordinated prior to a scan visit? Part of our effort consisted of understanding site conditions such as accessibility details and security requirements. With this, we’d ensure our scanning team could access the plant smoothly every day and make the most out of their time onsite. While the following items are typical for most of our scanning projects, the complexity of this facility required extra attention. Let’s dive into the specifics:

• Certificate of insurance (COI): clarifying the client's insurance requirements prior to scheduling the scanning date is important given that some specific requisites take considerable time to process.
• Other certifications: due to ongoing construction in the plant, all surveyors were required to hold OSHA certification dated within the last three years. This demanded many technicians to complete a 10-hour course before the site visit.
• Safety trainings: a 40-minute safety training was required for each technician on their first day.
• PPE: Steel-toe boots, safety glasses, hard hats, and vests were mandatory. Earplugs for noisy areas, recommended.
• Arrival time and onsite schedule: the team would need continuous escort by site personnel. We’d arrive onsite at 6 am daily and conduct scanning during business hours and the first shift. Cutoff time would be 4 pm.
• Equipment drop-off: given the campus size, we had to determine the closest drop-off point for our team’s extensive amount of equipment.
• Equipment onsite storage: since this was (initially) a 4-week scanning effort, we had to make sure our client allocated a room where our team could leave and charge the equipment overnight.

The scanning strategy and logistics:

Our initial and high level strategy consisted of scanning the facade and setting up control around the building boundary, and then transitioning to the interior. The target was to start scanning from bottom to top, beginning as low as possible, in this case, at the subbasement level. As the exterior was weather dependent and the mobilization was scheduled for March, we’d prioritize those areas during clear weather periods of time.

The survey and scanning teams would operate simultaneously and try to remain at the same level or in adjacent areas to facilitate the escorts work. This would also ensure continuity of the scanned data, minding that jumping around was detrimental for the sorting and registration process.

The crew would be flying in from various locations, so we designated Mondays and Fridays for travel to and from home, leaving Tuesdays, Wednesdays, and Thursdays for scanning activities. By concentrating extended scanning sessions on these three days, we aimed to streamline operations by reducing check-in and check-out times as well as minimizing mobilizations to the storage room that was located outside the plant.

The site challenges:

The first week of March 2024, the crew arrived at the plant. I would be lying if I said the scanning work ran smoothly all the time, yet we were always ready to regroup, discuss, and decide on our course of action promptly. Given that the plant was operational and undergoing constant construction, it consistently experienced high foot traffic. As visitors, our commitment was to adapt to this dynamic environment, scan areas with minimal disruption, and closely adhere to our scanning plan whenever possible. Despite our thorough planning to make our work more predictable, the following are some of the challenges we faced:

• The labyrinth: the primary challenge was effectively strategizing scan areas and connection points, especially between levels and platforms at different elevations. The plant was very complex for newcomers, and the field team found themselves recursively looping back to areas they had already scanned.
• Obstructions on the floor: the presence of numerous pallets on the floor where elevated scans were necessary to capture large equipment slowed our progress more than anticipated.
• The weather: the complexity of the interior scanning effort led us to prioritize it over the roof, leaving this area for the end. Unfortunately, heavy rain in the final week forced us to postpone roof scanning by a week.
• The ongoing construction: certain areas presented multiple active crews along with extensive scaffolding, causing significant line-of-sight issues. Based on our experience, safely climbing scaffolding with scanning equipment is time consuming, and the data coverage gets affected due to obstructions regardless. Since the crews could not vacate the area, we collaborated closely with the client and escorts to understand the construction schedule and find times when no other crews would be working nearby, such as early mornings before workers arrived. Despite these efforts, the area took approximately four times longer to complete than initially planned since repeated and fragmented visits were necessary to ensure proper coverage. Additionally, we had to strategically position the scanners to prevent them from being bumped or knocked over and add extra shots to get around scaffolding and barriers while accommodating the active crews in the areas.

• Flooding: water on the floor is a quite common issue in projects of this nature, and it can lead to reflections in the scanned data, making it unusable. To ensure accurate capture, we needed to minimize these reflections as much as possible otherwise, we would be risking ground data. We coordinated with site personnel to revisit the affected locations several times, but unfortunately, the problem persisted. As shown in the pictures below, we had to remove a significant amount of floor data from the point cloud deliverable (pic on the right):

• Narrow and complex catwalks: the tight catwalks made it difficult to achieve adequate and sufficient scan overlap and nearly impossible to control the targets. To ensure precise registration, scans had to be meticulously positioned so that each floor could be accurately aligned with both the floor above and below.

The equipment

About time! I’m sure you’re curious about the equipment we brought! ??

For laser scanning, we deployed three Leica RTC360 terrestrial scanners, along with three lightweight carbon fiber tripods and two heavy-duty extension tripods. To establish control, we utilized the Trimble Focus 35 robotic total station paired with the Trimble R12i RTK GNSS system receiver.

Custom rectangular checkerboard targets were strategically placed throughout the project site and located using the survey control equipment. These stickers were captured in numerous shots distributed evenly throughout the facility in an effor to constrain scans to known locations and provide a quality and accuracy metric during the processing phase.

Additionally, we utilized four precision machined Leica checkerboard 'tilt & turn' round paddleboard targets. Unlike the targets, these were not located by the survey crew (but the scanning one), and had no location values established since they were used only as a portable supplemental registration aid between scan setups.

At one point during our planning phase, we considered bringing a handheld scanner for small and hard-to-reach areas. However, decided against it it because integrating data from both scanners would have been very time-consuming and wouldn’t ensure the accuracy we needed.

Registration challenges:

In all honesty, our rockstar partner managed to register this substantial project smoothly and efficiently. They asked the right questions and consistently prioritized the needs of our modeling team.

The roof was one of the most challenging levels to register since the scan overlap from the level below was extremely limited. While the steam on the rooftop did not significantly impact the field efforts, its volume and density required extensive point cleaning during the registration process to prevent false point overlap. This forced to rely on survey control alone to keep the separate roof areas within accuracy and tolerance.

The facility's size and complexity posed substantial data management and project segmentation challenges. To achieve the high level of detail required for modeling, the field team ensured near-total coverage of all relevant elements, resulting in an unusually high number of scan positions.

Due to the excessive size of the sub-basement, basement, and ground levels, they thoughtfully divided these areas into separated zones to manage data size limitations during both field capture and office registration. Each field “project” could only contain approximately 300 scans before causing significant performance issues and making equipment crashes frequently.

Last but not least, and to maintain file usability, the facility was divided into several separate projects representing each level. In some cases, individual levels of the building approached the theoretical maximum limit for our partner’s scan processing software, leading to unprecedented technical difficulties and exponentially longer processing and export times. Consequently, many levels required further segmentation into sub-areas to produce manageable and usable final data.

The deliverables:

Here are more juicy details for the scanning folks! Our deliverables included colored point clouds with control and 360-degree panoramic views. To support the modeling work, we took one panoramic view at each scan location, adding up to 4,497 scans and photos. Here’s a breakdown by level with the corresponding scan counts:

Equally important for managing large amounts of data, here’s the naming convention we used to keep files organized:

ClientName_AreaCode_Level_FileFormat_Date

Example: XXX_1-B-BASEMENT_RCS_5-29-24

From our experience, including a timestamp is crucial to avoid confusion when dealing with multiple revisions of the same file. However, we’re proud to report that, thanks to incorporating survey control (and to our fantastic partners), once we set up the files with the correct coordinates, all point clouds were accurately positioned with no registration issues (seriously, I’m not exaggerating).

As far as survey control, we set up 155 points with the purpose of ensuring accuracy and facilitating the registration process, most of them represented with the sticker targets.

We used the client’s BIM360 hub for file transfers, which was ideal for centralizing all our deliverables and allowing stakeholders to upload their files to one shared location. Here’s how we structured our deliverables folder and some information about what each file format included:

01-RCS (unified point cloud): These were the primary point cloud files used for Revit modeling. We decimated the files to 5 mm and split them to keep each file under 15 GB.

02-LGS (panoramic views): This format was preferred by our BIM modeling team. LGS files can be opened using the free TrueView application from Leica, which was very convenient. We kept each batch under 25 GB to ensure easy download and manipulation.

03-Survey Reports: These included PDF floor plans showing the approximate locations of the measured points, along with CSV files detailing point attributes.

04-RCP (Recap Files): Although structured point clouds were not required, we provided RCP files as an additional option for accessing panoramic views using Autodesk software.

05-Raw Data (RTC360 Files): This category included various support files for archiving purposes.

The schedule:

Often times, with projects of this complexity, schedules don’t always go as planned, and this one was no exception. We initially estimated that four technicians would complete the on-site work in four weeks. However, due to a mix of expected and unexpected on-site challenges, logistical issues, and weather-related delays, the survey work finally extended to six weeks.

Additionally, aligning our deliverables with the facility's existing grid system also demanded substantial time and effort. We had to determine the files’ origin, rotation, and orientation while ensuring client and owner consensus to avoid future issues. Once the system was already established, we started to rotate and export all files, managing them across multiple machines. Finally, the processes of decimating, cleaning up, and transferring files proved to be significantly more time-consuming than anticipated. Below is a detailed overview of the actual scanning schedule:

Wow, that’s a lot of details, right? I warned you it was going to be a wild ride, and we’re not even halfway through! If there’s anything else you’d like to know about the scanning process, leave a comment and let me know. If you’re interested in how we navigated the BIM process, check out Part 3!