Leica GS18 T expands sites where GNSS can be used
In 2019, BM Field Co., Ltd., a surveying company in Hokkaido, Japan, added the GNSS RTK rover, Leica GS18 T, into their surveying toolkit and has used it on a wide variety of sites since. This has included irrigation canals, wilderness areas and even a landslide site. Working on these sites is easier because the GS18 T measures accurately with a tilted pole, eliminating levelling work requiring high concentration and extra time. The GS18 T has improved work efficiency, reduced costs and enabled GNSS surveys under more challenging conditions.
Virtual reference station surveying boosted by GNSS
BM Field, headed by Tomokazu Aoyama and based in Sapporo, Japan, is a private surveying company with a reputation for completing surveys in challenging conditions. Their customers are building and surveying companies that work with government bodies across the Hokkaido region.
"We've been involved in many agricultural surveys to gain an understanding of field areas and create land improvement plans. We’ve also conducted disaster prevention surveys to understand landslides and create recovery plans. And so we’ve gained a reputation as an experienced company capable of handling work in forests and on steep and rocky hillsides,” says Aoyama.
Surveying in challenging conditions
BM Field uses Leica Geosystems equipment to help make this challenging work possible. Even before he set up his own business in 2008, Aoyama was using Leica Geosystems’ products.
“Compared to other surveying instruments on the market, they were the most durable ones in their class. Since then, I’ve continued to use Leica Geosystems’ products because of their robustness and reliability. Even now, our instruments get wet in the rain all the time, but the Leica Geosystems’ products just shrug it off,” he says with a smile.
Aoyama purchased the Leica Viva GS08 plus in 2015 as the company’s first GNSS system. The GS08 plus receives signals from multiple satellite sources, including GLONASS and GPS, and signals are rarely blocked by tree branches or utility poles.
Before this purchase, the company did some GPS-based VRS and RTK surveys but had difficulties depending on location and time of day to get reception from the relevant type of satellite. Thinking that multiple satellite systems would expand the range of sites where surveying could be applied, Aoyama invested in a new GNSS system.
“On introduction, the impact was immediate,” he says. “It has greatly improved our on-site work efficiency.”
Tilt measurements eliminate 250 ladder ascents in an irrigation survey
At a 2019 trade show, Aoyama was introduced to the Leica GS18 T GNSS RTK rover. The “T” in GS18 T stands for tilt, referring to its tilt compensation.
“After hearing that it can measure accurately even with a tilted pole, without calibration, and that it is immune to magnetic disturbances, I strongly felt that this is what we needed,” says Aoyama. “And I was just about to work on the perfect project for it.”
The project was the survey of an agricultural irrigation canal with a height of more than 1 metre.
Without the GS18 T, surveyors would have needed to climb down into the canal and level the pole for each measurement. Since they couldn’t walk at the bottom of the irrigation canal, measuring the next point would mean climbing up the ladder with the GNSS system and then back down again to the next position.
The 5-kilometre-long irrigation canal was surveyed at an interval of 20 meters – repeating this method, they would have had to climb up and down 250 times, and it would have been very tough.
“When I tried out the GS18 T, I was impressed. It could take measurements with the tilted pole so there was no need to climb up onto the canal wall and no need to worry about the bubble. Also, there was no need to carry out troublesome calibration before starting work. So we were able to complete the on-site work in an astonishingly short time but with the same results,” explains Aoyama.
The company has taken measurements in locations that defeated conventional equipment, such as places where visibility is limited and in large areas of wilderness. Aoyama feels that with the addition of Galileo, the analytical capabilities of the system have clearly improved.
Aoyama continues to add Leica Geosystems GNSS technologies to his company’s surveying toolbox. In 2020, BM Field acquired the Leica Viva GS16 GNSS smart antenna and have now a system that makes RTK surveying possible with a small number of personnel.
Aoyama explains, “VRS can't be used in the field if there is no internet connection, but with RTK, you don't have to worry about the internet connection. If the GS16 is installed in a location with a good view to the sky and used as a base station, you can carry the GS18 T into thick undergrowth and still conduct a good survey using real-time corrections.”
Another advantage of RTK is that it can save on communication costs. Currently, the company is using RTK for 80 to 90% of its GNSS survey projects.
"By combining VRS and RTK, we've significantly expanded the range of applications for GNSS antennas," says Aoyama.
Surveying overgrown wilderness and other challenging sites
Let’s look at two more examples of sites where the GS18 T has strengthened the surveying capabilities of BM Field.
In the first project, BM Field was responsible for plotting slope details of a field to create a construction plan for under-field drainage.
"The site was a large agricultural field. I walked across it taking measurements at 20-metre intervals, and because there were no trees or utility poles to block the signal, the capabilities of GNSS were immediately apparent,” says Aoyama.
The second project was a disaster prevention survey. It was necessary to understand the current situation of an area before building a retaining fence to provide reinforcement and prevent landslides. In disaster recovery surveying, the boundary between the normal area to be maintained and the area that has collapsed must be clarified. So the GS18 T’s tilt compensation was very useful.
“On a steep slope about 15 metres high, there were many long piles from the old earth retaining fences, but the upper ones were ageing and had tilted diagonally. The underfoot conditions were so bad that if I couldn't measure with the tilted instrument, the job would have been impossible,” says Aoyama.
Measuring using a high pole (left) and a screen of the field software Leica Captivate (right)
Expanding survey and post-survey possibilities with GNSS
Currently, for topographic surveys (including route surveys), Aoyama prioritises the GS18 T and uses the Total Station in locations where the GNSS doesn’t fit the need.
“It all depends on the situation on the site. For example, in the case of the cedar forest in Aoyama prefecture, there were tall trees close together and we couldn’t use GNSS. So, for that project, I created some reference points and then measured these using the Total Station,” explains Aoyama.
However, Aoyama recommends GNSS in locations where visibility is poor, locations where detours must be made and locations where it is inconvenient to bring in heavy equipment.
“For people who say GNSS can’t be used because there are trees, I suggest they try RTK,” Aoyama advises. “Of course, if the site requires millimetre accuracy, I will opt for a Total Station, but if an accuracy of 1-2 centimetres is sufficient, I won’t hesitate to go for GNSS.”
Post-survey office work is also straightforward with GNSS.
The GS18 T and controller at the survey site utilise the 3D field software Leica Captivate in the Leica CS20 controller. After returning from the field, Leica Infinity office software is used to import the measurement data into a PC. Then, a plan view and vertical/horizontal cross-sectional views are created on a surveying CAD system.
“When you use Captivate on-site, it's convenient because you're constantly made aware of the accurate position and tilt of the pole,” reflects Aoyama. “The on-screen 3D viewer is also easy to read because of the sun mark and colour display features.”
Aoyama particularly likes the navigation function that indicates the next stakeout point on the screen with an arrow. Walking in the indicated direction brings you easily to the measurement point. This function is visually and intuitively easy to use and is especially helpful when moving crosswise.
Additionally, Infinity has improved data analysis and saved time from potential rework for BM Field.
“Infinity offers a higher degree of freedom and adaptability than software by other companies," says Aoyama. “For example, you can change the detailed settings between elevation/descent, use/do not use satellite signals, and so on. This means there is scope for some trial and error in the analysis of the data. In fact, thanks to this flexibility, there have been several occasions where we avoided having to redo site measurements.”
Faster on-site work and cost reductions boost competitiveness
Introducing the GS18 T has brought BM Field several benefits, expanding the range of sites where GNSS can be used and increasing on-site work efficiency
As the GS18 T can be combined with the GS16 to perform RTK, it is now possible to conduct GNSS surveys at sites with adverse conditions, including lack of internet connectivity. Additionally, data can be received from a broader range of positioning satellites. This, together with the improvement of data analysis, has enhanced the capabilities.
By using GNSS extensively, BM Field has also increased the range of sites where measurements can be taken with a very small number of personnel, leading to a reduction in costs. Similarly, since it is no longer necessary to keep the pole vertical, far fewer person-hours are required for on-site work.
A plan view created by surveying a 10ha wilderness
“In the product introduction of the GS18 T, it says 'work productivity is increased by 20%. But the increase is much higher than that. As an example, a project which would otherwise have taken 30 days before was completed in 10 days, we are now able to do double or triple the work,” says Aoyama.
This has also brought an increase the profits and differentiates BM Field from its competitors.
BM Field is well regarded by its customers for efficiently implementing both VRS and RTK and their knowledge of implementing GNSS in difficult conditions. This has increased work orders from nationwide construction consultancies in Aomori, Iwate and other areas outside Hokkaido.
As his next move, Aoyama is considering the GNSS receiving antenna Leica GS18 I, which uses Visual Positioning technology.
“I'm always hoping that I'll be able to do more GNSS surveying in adverse conditions that I currently have to give up on. One solution would be the capability to use images to measure point coordinates,” says Aoyama with optimism.Aoyama’s expectations for the future evolution of Leica Geosystems GNSS surveying technology are high, including the potential for BM Field to use these technologies to master new surveying challenges.