Comparing Airborne LiDAR with Bathymetric Data: How Terra Brasil Uses LP360 for Merging, QA/QC, and Deliverables
Published in the Jan/Feb 2025 edition of LiDAR Magazine
Since its establishment in 2009, Terra Brasil has set a high standard of excellence in the fields of topography, bathymetry, and hydrometry in Brazil. Starting with conventional techniques like Total Station surveys and traditional bathymetry, the company has continually evolved, embracing technological advancements to enhance its service offerings. In 2020, Terra Brasil expanded its portfolio to include aerial photogrammetric applications and hydrometry using Acoustic Doppler Current Profilers (ADCPs). The year 2023 marked another significant milestone as the company integrated LiDAR technologies and advanced modeling software into its operations.
Leading the way is CEO and civil engineer Thadeu Ribas Lugarini, who has been instrumental in steering Terra Brasil towards innovation and technological integration. “We were making technical advancements in the company, and the aerial survey market in topography grew significantly with the advent of aerial photogrammetry,” says Thadeu. “So, we decided to incorporate TrueView aerial LiDAR, from GeoCue, as we already had extensive expertise in GNSS systems, drone-based surveys, and cartography.”
Adopting GeoCue’s TrueView LiDAR and LP360 Software
Terra Brasil’s quest for a reliable and efficient LiDAR solution led them to GeoCue. “We were looking for a LiDAR solution,” recalls Thadeu. “We liked GeoCue for its customer service and the LiDAR’s capability to produce realistic and accurate points. Additionally, LP360 provided us with a lot of confidence as it’s software that both generates and processes the point cloud. This allowed us to use a single software for generating and managing the LiDAR point cloud.”
The integration of TrueView LiDAR systems with LP360 software updated Terra Brasil’s workflow. “The LP360 system enabled the generation of the LiDAR point cloud and the Digital Terrain Model in a single package,” explains Thadeu. “But the most satisfying aspect was working with a model that updates automatically after point classification handling. Easy export, import, and point cloud merging—all these factors contribute to making LP360 a comprehensive software solution.”
One of the key features of LP360 that stood out for Terra Brasil was its ability to integrate LiDAR point clouds with bathymetric data seamlessly. “This involves integrating the LiDAR point cloud with a point cloud imported from a TXT table containing elevation and planimetric data from bathymetry,” says Thadeu. “Once merged, all that remains is to work with the digital terrain model.”
To highlight the impact of LP360 on their operations, Lugarini shared three significant hydroelectric projects undertaken by Terra Brasil. These projects demonstrate how the company integrates airborne LiDAR data with bathymetric measurements from lakes and dams using LP360. By leveraging the software’s advanced capabilities, Terra Brasil ensures rigorous QA/QC processes, producing highly accurate models and volume analyses essential for critical infrastructure management. These ventures not only underscore Terra Brasil’s technical expertise but also showcase the remarkable results achievable through cutting-edge geospatial technology.
Case Study 1: Pedra Reservoir Project
The Pedra Reservoir project was a significant undertaking that showcased the capabilities of LP360, even independently of GeoCue equipment. “In the case of Pedra, we did not conduct Drone LiDAR topography,” notes Thadeu. “So, I used LP360 entirely independently of GeoCue equipment, demonstrating that the software can be used for cartographic data generation.”
The process involved integrating bathymetric data with topographic data provided by Eletrobras (Chesf). “First, I received contour lines of the dry area from Eletrobras as the data was provided,” explains Thadeu. “I converted the contours into points spaced every one meter using GIS software. Then, I imported the tabulated points as LAS using LP360’s import system. I applied the same method for the bathymetric points.”
Conducting bathymetry over a 42 km² area presented several challenges. “The challenge was executing lines every 30 meters while maintaining the linearity of the projected line diagonally and following the same standards despite strong waves and winds in the region,” recalls Thadeu. “All these factors complicated navigation and brought significant challenges to our team. But with a lot of effort, we managed to complete the bathymetry after five months in the field to complete the entire service.”
The ability to generate a 3D model and extract volume and area data was invaluable for Eletrobras’s reservoir operations. “The information regarding volume and area data from the 3D model allows for the analysis of volume and area at each elevation of the reservoir,” says Thadeu. “This information is crucial for maintaining the hydrological management of the sluice gates and for energy generation at the hydroelectric plant.”
The final deliverable was comprehensive. “The final deliverable is the digital terrain model in raster format for the entire reservoir of the hydroelectric plant, with elevation information every five meters, which corresponds to the raster pixel, along with the Area-Volume Curve Table, which indicates the volume and area for each elevation of the reservoir at every 10 centimeters,” explains Thadeu. “This includes information on the reservoir’s volume at the maximum elevation (the highest level the reservoir can reach), the normal maximum elevation (the maximum level at which the reservoir is maintained without spilling water), and the normal minimum elevation (the dead volume level).”
Case Study 2: Hydroelectric Plants in Paraná
In another significant project, Terra Brasil utilized the TrueView 540 LiDAR system and LP360 software for hydroelectric plants in Paraná. “In Paraná, we used the TrueView 540 to map the edges of the reservoirs at the Fundão and Santa Clara power plants, which are part of Elejor, hydroelectric plants on the Jordão River,” says Thadeu.
Similar to the Pedra project, bathymetry was conducted using a single-beam echosounder. “We conducted bathymetry with points spaced every two meters along the survey line and 40-meter spacing between lines,” explains Thadeu. “We used LiDAR to map the dry area of the reservoir, and then the 3D model was generated by integrating LAS files from both the bathymetry and the topographic area of the dry land.”
hydroelectric plants in the state of Paraná.
The data provided to the National Water Agency (ANA) was critical for regulatory compliance and operational efficiency. “The National Water Agency regulates the operation of hydroelectric plants dispatched in Brazil through norms and guidelines designed to ensure the correct functioning and operational quality of these plants,” said Thadeu. “One of the controls required by the National Water Agency is the updating of the Area-Volume Curve for these plants so that they can present their data on volume, area, and elevation for operations at maximum maximum elevation, normal maximum elevation, and normal minimum elevation, which are also related to useful volume.”
LP360 facilitated this process seamlessly. “All this data is extracted from the 3D model of the reservoir generated in LP360,” says Thadeu. “Before using this software, I had to work with multiple GIS software to arrive at the digital terrain model. Now, it is possible to work with the generation of the LiDAR point cloud, integration of bathymetric and topographic data, generate the terrain model, and adjust that model all within the same software, LP360.”
The final deliverables were comprehensive and met all regulatory requirements. “The data is shared through the delivery of the digital terrain model, the cartographic products that generated the model, as well as geodetic benchmarks, quality control through control and check points, a local geoidal model that adjusted ellipsoidal altitude to orthometric altitude, bathymetric points, and finally, the spreadsheet with the data for the Elevation x Area x Volume curve, which details the area and volume for each elevation of the reservoir,” explains Thadeu.
Case Study 3: Companhia Siderúrgica Nacional (CSN) Project
The projects with Companhia Siderúrgica Nacional (CSN) in Rio Grande do Sul were particularly significant, especially in light of the recent catastrophic flooding in the region. “The projects with CSN in Rio Grande do Sul started before the flooding in the region,” notes Thadeu. “We updated seven reservoirs for CSN in the state, all of which were completed before the floods occurred.”
After the flooding, Terra Brasil returned to one of the plants for additional mapping. “After the event, we returned to the Canastra plant as it had dried up due to repairs that will be carried out on the plant because of the damage caused by the flooding,” says Thadeu. “We conducted mapping of the dry plant using TrueView 540, which we had previously mapped the dry area with the TrueView 515.”
Using both the TV515 and TV540 systems allowed for comprehensive mapping before and after the reservoir dried out. “In both cases, we used LiDAR mounted on the DJI Matrice 300, supported by GNSS from Trimble,” explains Thadeu. “The flights were conducted at an average altitude of 70 meters, with an average speed of five meters per second.”
The key findings from the topographic comparison are pending, but they are expected to provide valuable insights. “We have not yet conducted the comparison, but the volume of both models will indeed be compared, and the accuracy of the bathymetry can be evaluated, as compared to the drone LiDAR,” said Thadeu.
The final results included updated reports and comprehensive data sets. “We created reports updating the Area-Volume Curves for the seven reservoirs, containing cartographic information on the topography of the dry area, bathymetry, geodetic benchmarks, control sections for sediment monitoring, and digital terrain models for each hydroelectric project,” says Thadeu.
Technical Insights and Challenges
Integrating bathymetric data with LiDAR topography presents several technical challenges. “The biggest challenges were integrating data with varying point densities,” explains Thadeu. “LiDAR provides thousands of points per square meter, while bathymetry with a single-beam echosounder offers points spaced every two meters, with bathymetric lines spaced up to 200 meters apart, resulting in a rich TIN model in the dry topography area and a triangulated model in the wet area.”
LP360 plays a crucial role in performing Quality Assurance/Quality Control (QA/QC) on the acquired data. “Control points are very useful for analyzing the accuracy of the survey,” says Thadeu. “We executed as many control points as possible, while also surveying cross-sections along the edges of the reservoir using a Total Station to assess the accuracy of the LiDAR.”
He adds, “If possible, it is beneficial for the check points to be identifiable on the ground so that any error can be identified. Quality control is generated from the export of the report on the check points, measuring all errors and the average error of the survey.”
The accuracies achieved with GeoCue’s TrueView have been impressive. “The accuracies achieved so far with the use of GeoCue’s TrueView have been very good, with all point clouds exhibiting errors ranging from one to ten centimeters, depending on the flight parameters,” notes Thadeu.
Describing the process of TIN interpolation of LiDAR and bathymetry data within LP360, Thadeu says, “The TIN interpolation process is one of, if not the oldest interpolation methods in surface generation programming. In LP360, I have always had good experiences with TIN, and the export function allows for the creation of a lightweight file that is easy to handle in GIS software.”
He emphasizes the efficiency of LP360 in manipulating point clouds. “As mentioned, LP360 greatly benefits from its ability to manipulate the point cloud through classification and simultaneous surface updates, where the final loading is only done during export,” says Thadeu. “This practice significantly saves time when generating a terrain model.”
Advice and Recommendations
For professionals looking to integrate bathymetric and LiDAR data, Thadeu offers valuable advice. “My advice is to look for software that is efficient for data integration, like LP360, and to always use the same planimetric and altimetric reference so that both pieces of information can be integrated without causing breaks in the model,” he says.
He also shares best practices developed while working with LP360 and TrueView systems. “My practice is always to work with the altimetric reference in ellipsoid, as I mentioned, because it aligns with the reference of the standard GNSS system, where most GNSS devices operate with ellipsoidal data,” explains Thadeu. “Regarding TrueView, I always recommend maximum organization when working with point clouds, as each flight cycle generates a point cloud package. In extensive projects, maintaining organization is crucial to ensure that no flight or cycle is missing from the project.”
Using the Right Technology
GeoCue’s TrueView technology has allowed Terra Brasil to undertake larger and more challenging projects. “GeoCue has enabled us to undertake significant projects with LiDAR, and I would like to thank the team for their partnership and support.” he says. “We are now considering purchasing the TrueView Go, which would be our third acquisition from GeoCue, and it will undoubtedly allow us to execute many more great projects.”
By using GeoCue’s TrueView LiDAR systems and LP360 software, Terra Brasil has boosted their abilities, delivering precise and detailed data for important infrastructure projects. Their story inspires others to embrace LiDAR technology to improve efficiency, accuracy, and impact in their own work.