Mission Planning with the Zenmuse L1/L2 for Lidar and Photogrammetry

This article covers the basics of planning lidar and photogrammetry missions with the DJI M300/M350 drone and Zenmuse L1/L2 sensor.

L1/L2 Lidar

Lidar is a great option if a ground model is needed for a vegetated area. These specific settings will cover recommendations for data capture in vegetated areas, but different settings may be needed depending on the environment.

It should be noted that ideal Lidar data collection settings vary from site to site, and a few key settings should be considered. While our recommendations are a good starting point for a bare earth model, it is good to be mindful of variations in vegetation that necessitate changes in flight and payload settings.

Speed: If a site is mostly grass and weeds, the speed can be set to the maximum (L1 9m/s, L2 15m/s) to decrease data collection time. If thicker vegetation, such as scrub/shrubs and tree canopy cover, is in place, slowing the speed down to 75% or even 50% of the maximum is suggested to allow pulses to reach the surface.

Side Overlap: If you aren’t concerned with the quality of the orthophoto, an overlap of 50% (L1) or 20% (L2) is sufficient for a bare earth model to be exported into a CAD program for design or estimating purposes. If a quality orthophoto is required, default to ideal photogrammetry settings.

Return Mode: The canopy height and density should dictate the data collection settings. Adding triple, quad, or penta return will produce returns through most vegetated conditions. Single and dual should only be used with grass and taller weeds on site.

Return mode dictates the number of times a pulse is sent and received by the sensor:

Lidar Returns Infographic.png

1. To begin, power on the controller to access the DJI Pilot 2 app.

2. Connect to a WiFi network or hotspot to ensure base maps will load to assist with mission planning.

3. From the DJI Pilot 2 main menu, tap Pilot 2.

DJI Pilot 2 Homescreen M300 M350 RTK.png

4. Tap Flight Route

5. Tap the + at the top-right and select Create a Route.

6. Select Area Route.

7. Locate your site by panning around the map and using two fingers to adjust the zoom.

8. Drop a pin to start creating your survey area by tapping on the screen on the boundary of your site.

To move a pin, tap and hold to select it and drag the pin around with your finger. You can delete the selected pin by tapping the trash icon or by double-tapping on the pin.

9. After points are dropped to define the mission's boundary, tap the check mark at the top-left. If the settings don’t appear, tap the double arrows at the top-right portion of the screen to expand them.

10. Navigate through the settings listed below to set up your mission. Remember that our recommendations differ somewhat between the L1 and L2 sensors.

Mission Setting	Set to	Question to Ask Yourself	Reason
Drone / Camera	M300/M350 RTK L1/L2 - LiDAR Mapping	Is this a LiDAR mission or a photogrammetry mission?	Both LiDAR and Photogrammetry missions can be flown with the L1/L2
Collection Type	Ortho Collection	N/A	Select Ortho Collection to collect straight-down photos during the mission
Ortho GSD	Default	Do I need to achieve a specific ground sample distance for this flight?	View the GSD estimate to get a sense of what resolution to expect with the current settings. Keep in mind that manually increasing or decreasing the Ortho GSD value will alter other mission settings such as flight route altitude.
Altitude Mode	Relative to Takoff Point (ALT)	What elevation is your target altitude referenced to?	Unless you are referencing to altitude above Sea Level (ASL) in the EGM96 geoid model, set this to ALT.
Route Altitude	200ft (60m)	How high should I fly relative to the takeoff point?	Collecting LiDAR above 200 feet can impact accuracy of the data
Elevation Optimization	Disabled	Is my terrain or altitude expected to vary during flight?	When enabled, the drone will take a few oblique images at the end of the flight. You do not need these to process your data with Propeller.
Safe Takeoff Altitude	User Choice	How high should the drone be before it can safely fly to the start point?	If there are any vertical obstacles between your takeoff location and the starting location, consider raising this elevation.
IMU Calibration	Enabled	N/A	If this setting is turned on, the drone will fly forward for 30m and then fly backward 30 m at the beginning of each line. This is necessary to generate a highly accurate model.
Speed	L1 - 9m/s L2 - Max Speed Allowable (short vegetation and bare ground ONLY)	Should I slow the drone down?	If a denser point cloud is the goal or if there is more significant vegetation on site, slow the speed of the mission down to 75% or 50% of the maximum.
Course Angle	User Choice	What direction should I fly to cover the survey area?	Adjust for an efficient flight path and minimal lines.
Upon Completion	Return to Home	What should I do after completing the mission?	Safety and not losing your drone. Once completed, the drone will make its way back to the home point automatically.

Advanced Setting	Set to	Question to Ask Yourself	Reason
Target Surface to Takeoff Point	0	Is the terrain I want to survey at a different altitude than my homepoint?	Unless the terrain you are surveying is at a very different altitude than your takeoff point, leave this setting at 0.
Side Overlap	L1 - 50% L2 - 20%	How much should each image overlap with other images?	This will give enough overlap for some missing or poor quality images and still build a contiguous model.
Forward Overlap	L1 - 80% L2 - 70%	N/A	N/A
Margin	0	How much margin do you want to leave around the survey area?	Provided that your flight boundary covers the entire area you wish to survey, you don't need any margin.
Photo Mode	L1 - Timed Interval Shot L2 - Distance Interval Shot	What metric is used to capture images?	Timed interval shot has better results when flying at 9 m/s.
Custom Camera Angle	Disabled	N/A	Keeping this setting disabled will ensure your camera angle stays nadir (-90) and ideal for mapping.
Route Start Point	User Preference	Where do you want your mission start point to be located?	Tapping the points on your mission boundary will allow you to set the start point location and update your flight route. Conserve battery by selecting the most ideal start point relative to the takeoff location.
Takeoff Speed	User Preference	How fast should the drone take off?	Faster takeoff speeds will slightly reduce the battery voltage but may be necessary on active sites.

Payload Setting	Set to	Question to Ask Yourself	Reason
Return Mode	Set to Conditions	Is my site heavily vegetated?	If a site has less vegetation (grass/none), single and dual return will suffice. If a site has denser vegetation, use triple, quad, or penta return for a denser point cloud.
Sampling Rate	L1 - 160KHz L2 - 240KHz	Is a dense point cloud needed?	This value indicates the number of points collected within a given time. The higher this is, the more measured points there will be.
Scanning Mode	Repetitive	Does the site include heavily vegetated areas still? Are there complex structures I'm interested in over accuracy?	Using the repetitive scan mode narrows the frame of view of the sensor, while increasing the accuracy of points. By selecting non-repetitive, the sensor will have a much larger frame of view, but will be less accurate.
RGB Coloring	Enabled	N/A	If RGB coloring is disabled, Propeller will be unable to process the mission data.

Camera Slider Bars	Set to	Question to Ask Yourself	Reason
Image Ratio	L1 - 3:2 L2 - 4:3	How much of the image should I delete?	Utilize the whole sensor.
Image Format	JPG	How should the images be saved?	Images must be in a JPG format to upload to Propeller.
Mechanical Shutter	Enabled	Do I want my camera to use the mechanical shutter?	A mechanical shutter uses the conventional front and rear shutter curtains at the front of the sensor. Not using the mechanical shutter will introduce distortion.
White Balance	Set to conditions	What conditions should I accomodate for?	Adjust the setting to reflect current weather conditions. Setting the white balance incorrectly will result in poor stitching and/or inaccurate coloring of your model.

11. After you have inputted all the settings, tap the save icon.

Before flying the mission, please review our ground control recommendations. If AeroPoints are used for ground control, photos must be submitted with your lidar data.

Some images may be removed in the production of the orthophoto due to poor quality or insufficient overlap. We recommend customers verify that AeroPoint / ground control placements are within the flight boundary to prevent their removal from the overall survey deliverable.

L1/L2 Photogrammetry

The Zenmuse L1/L2 can also be used for standard photogrammetry without lidar. For the best results, we recommend flying distinct lidar and photogrammetry missions rather than combining the data collection in a single flight.

Begin by creating a route as outlined above in steps 1 through 9.

1. Once your mission boundary has been placed, select the L1/L2 Camera Model and Photogrammetry Lens.

2. Adjust the settings based on our recommendations listed in the table below. If you encounter settings in the app not mentioned in this table, leave them at their default.

Mission Setting	Set to	Question to Ask Yourself	Reason
Drone / Camera	L1/L2 Photogrammetry	Which camera are you planning on using for this mission?	The mission parameters will be different for different lens, so make sure this is set accurately.
Collection Type	Ortho Collection	Do I need vertical faces captured in my model?	Select Ortho Collection if you do not need vertical faces to be captured in high detail.
Ortho GSD	Default	Do I need to achieve a specific ground sample distance for this flight?	View the GSD estimate to get a sense of what resolution to expect with the current settings. Keep in mind that manually increasing or decreasing the Ortho GSD value will alter other mission settings such as flight route altitude.
Altitude Mode	Relative to Takeoff Point (ALT)	What elevation is your target altitude referenced to?	Unless you are referencing to altitude above Sea Level (ASL) in the EGM96 geoid model, set this to ALT.
Route Altitude	200-400ft (60-120m)	How high should I fly relative to the takeoff point?	The height is a balance between how quickly you would like to complete your survey (higher makes it faster) and the ground sampling distance that you need.
Elevation Optimization	Disabled	Is my terrain or altitude expected to vary during flight?	When enabled, the drone will take a few oblique images at the end of the flight. You do not need these to process your data with Propeller.
Safe Takeoff Altitude	User Preference	Are there obstacles in my takeoff area?	Set the Safe Takeoff Altitude to be higher than the tallest obstacle in your area.
Speed	Max Speed Allowable*	How fast should I fly?	*Unless you're trying to reach the required 10min mission time, increase the speed to minimize overall flight time. In low light conditions, reduce the speed and the shutter speed to ~1/800.
Course Angle	User Preference	What direction should I fly to cover the survey area?	Adjusted with the slide. Fewer turns means more area covered per battery.
Upon Completion	Return To Home	What should I do after completing the mission?	Safety and not losing your drone. Once completed, the drone will make its way back to the home point automatically.

Advanced Setting	Set to	Question to Ask Yourself	Reason
Target Surface to Takeoff Point	0	Is the terrain I want to survey at a different altitude than my homepoint?	Unless the terrain you are surveying is at a very different altitude than your takeoff point, leave this setting at 0.
Side and Front Overlap Ratio	~80%	How much should each of the images overlap each other?	This provides enough overlap for if some images are missing or poor quality, while still building a contiguous model. The lower the detail on the surface below, the higher your overlap should be. If you have a large area to survery, you can look at reducing the horizontal overlap (no lower than 60%) to increase the area you can cover per battery.
Margin	0	How much margin do you want to leave around the survey area?	Provided that your flight boundary covers the entire area you wish to survey, you don't need any margin.
Photo Mode	Distance Interval Shot	What metric is used to capture images?	Distance shooting allows the drone to capture images with consistent overlap.
Custom Camera Angle	Disabled	N/A	Keeping this setting disabled will ensure your camera angle stays nadir (-90) and ideal for mapping.
Route Start Point	User Preference	Where do you want your mission start point to be located?	Tapping the points on your mission boundary will allow you to set the start point location and update your flight route. Conserve battery by selecting the most ideal start point relative to the takeoff location.
Takeoff Speed	User Preference	How fast should the drone take off?	Faster takeoff speeds will slightly reduce the battery voltage but may be necessary on active sites.

3. Tap the save icon to save your settings.

4. Navigate to the camera settings by tapping the live camera view. The map and camera view will switch places.

5. Adjust the camera settings as described in the table below. When you encounter settings in the app not mentioned in this table, leave them at their default.

Camera Setting	Set to	Question to Ask Yourself	Reason
Mode	S (Shutter Priority)	How should the exposure be controlled?	To avoid motion blur. Shutter priority tells the camera that a fixed shutter speed must be used. The camera can adjust the exposure with apeture and ISO.
Auto Exposure (AE)	Unlocked	Can the camera auto-adjust exposure?	In order for the camera to be able to adjust the exposure with aperture and ISO, this needs to be unlocked.
Shutter Speed	1/1000	How fast should the shutter close?	1000 is usually a good place to start for sunny conditions. In low light conditions, reduce the shutter speed to ~800 and lower the speed.
Focus Mode	AFC	N/A	PLEASE NOTE: The drone may automatically switch to Manual Focus (MF) at the start of each mission. This is expected, and no user input is required.

Camera Slider Bars	Set to	Question to Ask Yourself	Reason
Image Ratio	L1 - 3:2 L2 - 4:3	How much of the image should I delete?	Utilize the whole sensor.
Image Format	JPG	How should the images be saved?	Images must be in a JPG format to upload to Propeller.
Lock Gimbal While Shooting	Enabled	Do you want the gimbal to lock in place while it takes a photo?	Leave this on its default setting. This will help prevent blurry images.
Mechanical Shutter	Enabled	Do I want my camera to use the mechanical shutter?	A mechanical shutter uses the conventional front and rear shutter curtains at the front of the sensor. Not using the mechanical shutter will introduce distortion.
Dewarping	Enabled	Should dewarping be applied by the camera?	This will help improve the accuracy of your data. Disabling this setting can lead to lower accuracy.

Note that in winter, or low light conditions, there are special considerations to make. You may need to slow down the flight speed of the craft (to less than 10m/s) and adjust the shutter speed to 1/800 or 1/500 to allow enough light to hit the sensor.

Failure to do this can result in a high ISO and will reduce the quality of the images you capture.

6. Double-check your settings in the Preflight Checklist and ensure Dewarping is turned ON for best results. The Preflight Checklist will appear when you start your mission.

Check the airspace on your site before you arrive, and remember to charge your AeroPoints and drone batteries before your mission.

I still can't do it!

We wrote these articles to equip you with everything you need to get the job done on your own, but we understand that sometimes this isn't sufficient.

If you're stuck, the Propeller hardware support team may be able to help. You can contact them by emailing hardwaresupport@propelleraero.com.au.

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Mission Planning with the Zenmuse L1/L2 for Lidar and Photogrammetry

L1/L2 Lidar

L1/L2 Photogrammetry

I still can't do it!