Capturing data during leaf-off conditions

Hi Rock Robotic Community, I am new to the Rock Robotic ecosystem and this is my first post. Any assistance is appreciated.
My company will be surveying an area of New Hampshire in mid to late-October. Since the leaves will already be turning and will be dry, how will this impact the results of a LiDAR scan? The area is heavily wooded and mountainous. Our primary concern is the foliage since this survey is for microwave communications, however we don’t have the ability to wait until next Summer. Instead, we plan to assume an additional 1.5 meters in height to account for the foliage. Does anyone have experience with scanning trees without leaves or as the leaves are changing (photoperiodism for you science-types)? We are using the R2A attached to an Easy Aerial Osprey.

1 Like

What the sun light can see, so too does the lidar.

Dry leaves will still block sunlight, so your scan will show trees with leaves.

Scanning without leaves will make nice model.

Fly slow and tight overlap.

You just want the tops of the trees?

I was also thinking about this… with the rock desktop software in the field, you can fly several test patterns and quickly visualize them in the field. This will give you an ability to calibrate your tools to produce the desired survey product and achieve the goals of the data.

Good luck!

1 Like
  1. Leaf Off vs. Leaf On Conditions: Trees without leaves (leaf-off condition) are more transparent to LiDAR pulses than trees with leaves. This means that during the leaf-off season, more laser pulses will reach the ground, providing a clearer picture of the underlying topography. On the contrary, during leaf-on conditions, a significant portion of the LiDAR pulses will be reflected by the leaves, which might obscure the underlying topography. However, given your focus on microwave communications, capturing data during leaf-on conditions might be more beneficial, as it will provide a better representation of potential signal obstructions during the majority of the year.
  2. Changing Leaves and Reflectivity: As leaves change color, their reflectivity can also change. Dry, changing leaves may not be as reflective as green, turgid ones. However, they will still contribute to the overall vertical profile of the forest canopy, which is essential for your microwave communication considerations.
  3. Compensating for Foliage: Adding an additional 1.5 meters to account for the foliage is a general approach and might not be accurate for all tree species or specific tree conditions. Tree species, age, and health can affect how much foliage a tree has and its distribution. The 1.5-meter addition is a buffer but may not represent the actual canopy structure in all areas.
  4. Multiple Returns: One advantage of LiDAR, especially in wooded areas, is its ability to record multiple returns. A single laser pulse can bounce off leaves, branches, and finally the ground, resulting in several return signals. This feature helps in differentiating between canopy layers and the ground.

Thank you for your reply to my question FlyingRadioWaves.
The tree canopy is my primary concern but my intention was to capture the terrain as well. For this project in NH, the hope is to be able to identify a specific tree that is blocking a Microwave Path so that it can be topped or removed. The owner of the property needs the tree identified and wants to see proof before he cuts down the wrong tree.
Also, our client would like to see the results for the entire path since they intend on using us and the LiDAR scanning for additional paths in order to identify future problems due to tree growth.

Thank you RR-Casey.Pryor, I appreciate your detailed reply.
This is good information that I will pass along to my team. I am feeling more confident about what we can accomplish knowing a bit more about what we can expect to see.

1 Like