Hello all, Lindsey asked me to forward this message from Katie White about UAS work going on in the Zealand Valley and possible opportunity for UAS work elsewhere with high tech sensors. Ian
From: Gryczkowski, Katharine - FS - <Katharine.Gryczkowski@usda.gov>
Sent: Monday, March 14, 2022 9:51 AM
To: Rustad, Lindsey -FS <lindsey.rustad@usda.gov>
Subject: UAS on the WMNF Fall 2022
Hi Lindsey,
Thanks for sharing with the WMNF Ecoteam last week. It was nice to hear an update on Hubbard Brook.
It may have been briefly mentioned in the call, but the WMNF is in the planning phases of a project to collect UAS lidar and imagery for an approximately 600-acre area around the Zealand River as part of a watershed restoration project.
The current plan is for a team from the Forest Service Geospatial Technology Application Center (GTAC) to fly the project in late Fall of 2022. This timeline is still dependent on a few variables, but I was asked to reach out to some people who might have
projects in the works that could take advantage of a GTAC crew already traveling to the region and renting equipment next fall. Does anything come to mind? It is my understanding that GTAC has to rent the equipment for a month regardless, so if they can combine
the timing of projects, the total price per project is quite reduced. There a meeting about the Zealand River Restoration UAS project today where some logistics of the project are going to be discussed, so I will mention I reached out to you.
Below are the specifications that the GTAC team provided on the equipment they plan on using:
In an effort to be completely transparent, here are some details about the technologies that will be used as well as and other project and cost considerations from our perspective.
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RCR will be leasing a lidar/RGB imagery sensor to conduct the survey. They plan to lease the
True View 515 from GeoCue. This system provides a PandarXT-32 lidar scanner, with the capability of two returns per beam/pulse, integrated with two RGB 20MP cameras aligned with the lidar scanner track.
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Conducting the acquisition at lower flight altitudes will provide relatively higher density and accurate data. GeoCue recommends acquiring data at approximately 75 meters AGL for standard topographic surveys which should result in about 210 first return points
per square meter for the True View 515 system in ideal conditions. Note that in areas with high vegetation density we would fly flight lines from 2 perpendicular angles to allow for multiple passes from multiple angles on the same spot and resulting in a much
higher point density in the final product. ( for more info see
https://geocue.com/wp-content/uploads/2021/04/210419-01-True-View-515-FAQ-002-TC_.pdf).
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Accuracy and precision of the collected lidar data is expected to be 4cm or less.
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Each RGB camera has a 63 degree field of view (FOV) mounted at a 25 degree angle from nadir. So it does not provide true nadir imagery. The FOV of the two cameras slightly overlap and flying at 50 meters to 60 meters AGL we anticipate getting ~1.5cm to 2cm
resolution imagery for this nadir to oblique imagery depending on the given location across the field of view of each respective camera. Given the requirements to fly at the required altitude to ensure quality lidar data, there would likely not be suitable
geometry in the imagery to create SfM products, but GTAC can assess it more after the fact when the data is available.
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RCR will also lease an appropriate small UAS platform (hexacopter) appropriate for carrying the True View 515 sensor system. We generally lease these platforms one week at a time.
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Due to the leasing requirements for the sensor, a minimum leasing period of one month is required. Based on market research, this requirement is typical. Shorter leasing periods are available from other vendors, but they are typically for higher performance
sensors and at a much higher weekly cost.
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In order to process the lidar data, a GPS base station will need to be operated in the local area of the AOIs and collect simultaneous survey-grade GPS data to be used for differentially correcting the lidar data during the post-processing stage. For this
project, this GPS equipment would be issued to RCR as government furnished property, though there is potential to use a CORs station that is gathering the required information and is within 25 miles of the site. (https://geodesy.noaa.gov/CORS/)
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Additional field time is also programmed as potential “reserve” or “foul weather” days (wind, rain, etc.) that may occur and preclude UAS operations for short or extended periods of time over the several days that will be required in the field to collect data.
In the event this time is not used in the field, we can apply it to other aspects of the project such as providing additional consultation, technical support, value-added processing/analysis of the data, etc.
- Collection of lidar data via UAS is a method we have begun to conduct this year, we have had successful data collection missions for mine subsidence in the Mark Twain NF, a variety of objectives
in Juneau, AK (including a dam survey, coastal shoreline mapping, mapping of heritage sites, etc), and we plan to collect lidar for multiple meadows in Region 5 for meadow restoration and monitoring purposes. The results of these efforts have taught us much
about the process and how to best collect data and create products. If you would like we can review data and lessons learned from these previous data collect missions with you.
Finally, while the products generated from this activity will be accurate to within 4 cm and have detailed resolution, they should not be considered as meeting the requirements for an official survey. To provide
that type of data, we would have to at least conduct this work under the direction of a licensed/certified surveyor
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