Author: Roger O'Neill
GroundTruth Exploration (GTE) has been delivering drone photogrammetry surveys for years, and as we all know, UAV photogrammetry produces stalwart deliverables that rarely disappoint except in scenarios with significant canopy. GTE wanted to deliver a more reliable terrain modeling service to their clients, and after substantial research, GTE decided to rent a GeoCue True View 410 3D Imaging Sensor (3DIS) for their 2020 summer field season.
About Groundtruth Exploration
GTE collects most of their data for natural resource exploration companies in remote and harsh northern Canada and Alaska. As a result, they are limited to the few warm summer months of the North. The GeoCue True View subscription model gave GTE an affordable method of dipping their toes into the world of LIDAR without spending hundreds of thousands of dollars on a LIDAR sensor for their short season.
The goal of the 2020 season was to develop a methodology to deliver a 4km2 standard bare-earth DEM product for GTE’s existing clients. Right off the bat, they knew that they would face challenges with handling large scale projects, however, despite the long list of difficulties and setbacks (including arson and a mid-flight failure of their M600) they were able to collect some unique datasets.
Capable of Exploring Inaccessible Territory
One of their first successful commercial surveys was for a placer miner in the Klondike Gold fields. This client wanted to determine if there had been any historic mine workings on inaccessible sections of his claims upstream. With the M600 drone and True View 410 3DIS, GTE was able to fly upstream to previously inaccessible claims and collect the necessary data. The finished product was beyond impressive. In the True View EVO software, GTE was able to strip off virtually all canopy and create a bare earth hillshade. In that hillshade they were able to identify distinct anthropogenic features that were most likely the product of the early miners of the Yukon (known locally as the “old timers”).
On an adjacent property, GroundTruth was able to conduct a similar survey in search of a historic copper mine adit that was rumored to exist in the hills above a placer claim. Again, they were able to survey the area of interest without having direct road access, and in the post- processing, they could easily identify the mine. These types of surveys were previously unobtainable with standard photogrammetric methods. For reference, they have included a DEM of the canopy to help demonstrate the canopy penetration of the True View 410.
The Mine adit - White Gold Corp
Large 8km^2 data set - White Gold Corp
DEM Projects Made Easy
Throughout the summer, GTE was also able to collect some large-scale bare earth DEMs for traditional hardrock mining clients. Some of their clients in the hardrock mining industry regularly use LIDAR-derived bare earth hillshades to perform surface lineation analysis. Topographical expressions at the surface of the earth can provide valuable insights about geological structure at depth. Below is a clip of an 8km2 bare earth DEM project that they were able to collect with the True View 410. In the image, you can clearly pick out the trenches, geophysics survey lines, and other subtle topographic features beneath the canopy.
Conducting Surveys Outside of Mining
One project was an archeological survey conducted for the Yukon Government and Trondek Hwech’in First Nations to help highlight the value of a historic caribou hunting camp on the Dempster highway. As a result of the survey, Archeologists were able to confidently establish a management boundary for the site identify at least three previously unreported cultural features and two additional geographic locations that warrant further investigation, and confirmed that the site was located on a former bed of the Blackstone River which may explain why older archaeological materials were not recovered from previous study areas.
Archeological site - Trondek Hwech'in First Nations
Analyzing Landslide Damage
One of the more unique projects of the season was to survey a massive landslide just off the Alcan highway. This project was particularly difficult because it was a remote helicopter access site. Additionally, the drone terrain following software could not rely on the public terrain data set because half of the mountain was missing. During this project, GTE pushed the limits of the True View 410/M600 combination. Over the main scarp of the slide there was so much missing material that the ground surface was outside the range of the scanner, and as a result, the True View 410 had difficulty getting sufficient point density in that section of the slide. The final bare earth DEM had large holes over the main scarp of the landslide due to the lacking point density. GroundTruth augmented this LIDAR survey with a traditional drone photogrammetry survey and was able to fill in the holes with the photo data.
Landslide - Yukon Geological Survey
Direct Comparison of Fixed Wing manned LIDAR vs. True View 410
Towards the end of their season, GroundTruth conducted a direct comparison of a fixed wing manned LIDAR survey at a standard 1m resolution and a True View 410 dataset at 25cm resolution. The True View 410 unit clearly outperforms the manned system in fidelity. Many more of the small surface features are distinguishable in the UAV dataset even in the areas of substantial canopy coverage.
Fixed wing comparison - White Gold Corp
In sum, GTE had an exciting first season as a UAV LIDAR service provider. The season was not without issues, but they were nonetheless able to pull through and provide some excellent results to their clients. GroundTruth is extremely satisfied with the first-class customer support provided by GeoCue. They proved that the True View 410 sensor itself is incredibly robust and can withstand some serious wear and tear in the field.
GTE plans on continuing to develop their UAV LIDAR services. They still feel like there is opportunity to improve upon their UAV LIDAR services by optimizing the post-processing workflow and investing in a more capable drone. GTE looks forward to the 2021 field season where they feel that they will be more prepared to go after the larger datasets.