Measuring the point cloud… with a GNSS rover
Takeaways from JTRS Registered Surveyor on the Leica GS18 I GNSS RTK Rover
Author: Renata Barradas
We measure the point cloud.
This is the slogan from JTRS Registered Surveyor, a professional land surveying company in Singapore that provides 3D laser scanning, land survey, aerial mapping and inspection, photogrammetry and imaging services. JTRS is continuously looking for innovative and creative ways to improve the surveying services the company provides.
The company's latest technology leap is being able to measure the georeferenced point cloud and points with its brand new tech acquisition – the Leica GS18 I GNSS RTK Rover.
"The capability of capturing images at the same time with real-time positioning from a single instrument, really changes the way we carry out surveying – It's a reality capture concept," explains Jimmy Tan, owner at JTRS.
Also, with the tilt compensation that comes with it, it helps in getting RTK observations and recording quickly, which is useful when working at night like we have to do at airport runways or MRT viaducts. I don't need an extra pair of hands to hold the torchlight to shine at the bubble while I level the pole."
Beyond measuring the point cloud, the GS18 I has empowered JTRS with a powerful RTK rover that combines fast RTK initialisation, tilt-compensated measurements and Visual Positioning, all in one tool. With GS18 I added to their portfolio, JTRS has been able to provide new services and improve the company's current services.
JTRS mostly uses the GS18 I for control surveys and quality checks in utility and construction projects. The tight accuracies needed range from 50mm to 100mm and for most QC projects within 40mm. For each project, the workflow with this versatile RTK GNSS rover is:
- Capturing the data using either the pole tip or Visual Positioning with the GS18 I and Leica Captivate field software
- Data processing with office software Leica Infinity
- Creating deliverables with: Infinity (to process images to point clouds), Leica JetStream (to publish the point clouds) and 3D Reshaper (to do mesh modelling based on point clouds).
In Tan's words, "With the GS18 I, I just need to point the camera onto the subject that I want to capture while walking. For example, in one of my projects, the time taken to survey the trial pit with the GS18 I was no more than five minutes. The time taken to post-process in the office using Infinity software was 30 minutes. I can produce true colourised point clouds, which I can export to orthophotos and also create digital surface models. It is also possible to create hundreds of topo points from the georeferenced images quickly and efficiently."
Safety and speed in a trial pit and as-built trench survey
Carrying out trial pit or as-built trench surveys can be very challenging. Surveyors usually need to follow the site contractors' workflow and schedule as the trench needs to be backfilled, and the road lane needs to be re-opened as quickly as possible.
When JTRS was tasked with a utility trench documentation, they saw it as an opportunity to put their new GNSS rover into a true test. Besides doing an as-built survey of trial pits and the underground utilities, the GS18 I allowed them to create a 3D point cloud and sequence it into a 3D mesh model.
The freedom of using both the pole tip and Visual Positioning to measure in the field and using simple workflow for processing in the office, pushes the boundary of surveying for JTRS to another level.
Confidence and accuracy in quality control check surveysFor a building and scanning project that included the 3D scanning of 1,200 blocks, JTRS carried the quality check of the georeferenced scanned data with the GS18 I. Once again, the tilt and Visual Positioning technologies on the sensor made it possible to access previously unreachable points.
"In one of our projects with HDB (Housing Development Board), I was able to pick up coordinates of points captured during my walk using Visual Positioning. With the GS18 I, it is convenient and fast to survey and I can get instant results before leaving the site.
When it was not possible to use the pole tip because it was too close to the building's edge and the RTK signal couldn't initialise we used the Visual Positioning method and walked further away from the building where there is RTK signal. Most of the time, we would use both methods if the site condition enables us to do so," describes Tan.
Smoother workflow + higher quality deliverables = confident clients
"Clients are more confident in the quality of the deliverables. With Infinity, I am able to process the images into true point clouds with accurate georeferencing. With Visual Positioning, I can capture two images per second as I walk, and each image comes with global coordinates from a single source – the GS18 I. It is like flying the drone installed with a GNSS antenna and camera, except we are walking," sustains Tan.
Opening new opportunities by measuring the point cloud
"We can further develop point clouds into a 3D mesh model – that's reality capture and it is very helpful in visualisation – many times better than a single point, single line or a 2D drawing. With Infinity you can also create Digital Surface Models. This is good for engineers or designers who can use this TIN model in their design work and easily extract heights and contours, water flows and more." says Tan.
The GS18 I is not only helping to improve the current services JTRS provides but helping the company to provide new services. Being able to create multiple deliverables faster and with fewer resources has led to more project opportunities.
If you want to hear and see more, listen to our webinar with Jimmy Tan.