How to Get Survey-Grade Accuracy from LiDAR Laser Scans!

Summary

In this detailed video, the process of using a terrestrial laser scanner to establish high-accuracy survey control is demonstrated. The speaker discusses their preparation for the GeoE 2025 conference, where they will present comparative analysis between UAS Lidar and terrestrial Lidar point clouds. The video walks through setting up GNSS control points, calibrating the Leica GS05 and P40 scanners, and dealing with environmental challenges like snow. The result is a precise, georeferenced point cloud that will be showcased at the conference, with a discount code for viewers planning to attend.

Takeaways

• 😀 GeoE 2025 is a major geospatial technology conference, and attendees can use promo code 'Rami 100' for $100 off their passes.
• 😀 The purpose of the survey is to create a ground truth dataset to compare with UAV LiDAR point clouds from a previous project.
• 😀 The survey involves seven GNSS-based control points for accurate georeferencing of the terrestrial LiDAR data.
• 😀 Special attention is given to a forested area near a bridge, which poses challenges for UAV LiDAR systems.
• 😀 GNSS equipment like the Leica GS05 is used to establish control points, ensuring high-accuracy positioning for the survey.
• 😀 Multiple control points are set up to ensure visibility for the LiDAR scanner and accurate data acquisition for the entire site.
• 😀 After establishing control points, a Leica P40 laser scanner is used to create high-resolution point clouds for analysis.
• 😀 The snow on the ground will add a slight elevation discrepancy, but scanning is still carried out despite environmental challenges.
• 😀 The Leica P40 scanner can collect up to 1 million points per second, providing dense and high-quality point cloud data.
• 😀 Three setups are used in the field, with careful placement of targets and consistent measurement to ensure accuracy for each scan.
• 😀 The scans are processed to create detailed point clouds of the site, with visualizations including grayscale and colorized data for further analysis.

Q & A

What is the main purpose of the laser scanning project described in the transcript?

The main purpose is to create a high-accuracy ground truth dataset using a terrestrial LiDAR scanner, which can then be compared to UAV LiDAR point clouds from previous surveys.

Which conference is the presenter referring to, and what is its significance?

The presenter refers to GEOE 2025 in Denver, Colorado, a major geospatial technology conference that gathers professionals from surveying, mapping, remote sensing, photogrammetry, and AI/ML fields.

Why are survey control points important in this laser scanning project?

Survey control points provide geodetic coordinates that allow the point cloud data to be accurately geo-referenced, ensuring that all scans can be aligned precisely with each other and with UAV datasets.

How many survey control points were used in this project and how were they observed?

Seven survey control points were used, and all were observed with a GNSS receiver to obtain precise geodetic coordinates.

Which equipment is used for establishing the control points?

A Leica GS05 GNSS receiver mounted on a bipod is used to measure the control points, after which a target is placed for the laser scanner to reference.

What is the Leica P40, and what are its scanning capabilities?

The Leica P40 is a terrestrial laser scanner capable of scanning up to one million points per second, producing dense, high-resolution point clouds suitable for detailed ground surveys.

How does snow affect the laser scanning data, according to the transcript?

Snow adds a small elevation offset, likely 1-2 tenths of a foot, to the ground measurements, slightly increasing the apparent elevation in the point cloud.

What process is followed to scan each setup location with the Leica P40?

The scanner is leveled, a new job is created, targets are identified and measured with their heights, and then the scanner collects the point cloud data, which can also be colorized with images for better visualization.

Why is it important to maintain line-of-sight between the scanner and the targets?

Maintaining line-of-sight ensures that the scanner can detect the control targets from each setup, allowing for accurate geo-referencing across multiple scans.

How does the presenter ensure the quality of GNSS observations for control points?

The presenter takes multiple RTK observations, aiming for high 3D quality with standard deviations under 0.01 feet, and waits until 100 observations are collected for consistency.

What additional uses does the laser scanner's image capture provide?

Images captured during scanning can colorize the point cloud and be used to stitch together a panoramic view of the site, enhancing visual understanding and presentation of the data.

What advice does the presenter give for improving survey conditions?

While scanning in snow is feasible, the presenter suggests repeating the survey in spring without snow for more accurate ground data and better environmental control.