Quick Start Guide: Phantom 4 RTK Data Collection


Propeller’s powerful tools rely on consistent globally accurate data. When surveying your site, the only way to obtain accurate data is through good ground control distribution and consistent flying practices.

Following these settings using a Mavic 3 Enterprise and AeroPoints should yield good results for basic data capture.

Certain edge cases require more thought and preparation.

Aside from the interference warning generated from being inside a building, verify no other warnings are posted in the status bar.
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Pre-flight preparation

Check flying restrictions for your site and follow the law.
Resources:

Charge the batteries for your drone and controller using the battery charger that came with your drone.

Ensure you have a recommended SD card in the camera.

Check for firmware updates that may be available by turning on and connecting the controller to the internet. 

  • Open the DJI Pilot app, then select the Status button in the top right corner to access the Health Management System to see which components need firmware updates.

Set the units and maps for your region.

Go to the GS RTK home screen

tap the menu, then

settings

Change the units to your preference.

Change map type to “Mapbox” from “Amap.”

Power down the drone, followed by the controller after adjusting the settings and updating firmware.

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Before leaving the office: Mission planning

Flight mission planning is easier if completed with an internet connection.

  • Using the on-screen map on the controller, or
  • Importing a KML file of the survey area into the app

1. Find out what coordinate reference system (CRS) your site is using. 

You'll require additional information if the site has a local calibration. If you aren’t sure, the project surveyor or engineer should be able to provide the CRS used.

2. Plan where you are going to launch the drone.

Launch from a higher elevation to avoid having insufficient overlap over the elevated parts of your site, which can result in holes in your model.

3. Plan your AeroPoint placement.

  • AeroPoints need a clear view of the sky and not be in the path of vehicles or machinery for the entire flight.

  • If you’re using a local grid system or are not covered by the Propeller Corrections Network, an AeroPoint must be placed on a known point.
  • The known point still needs a clear view of the sky and should rest on a flat surface (not sitting on/near a ledge).
  • Using a site rover, you can create a known point by recording the center of the AeroPoint (once it’s placed on the ground).
  • When processing the AeroPoint survey, you can input the rover recordings as the known point.

The Propeller PPK solution requires at least one AeroPoint to be placed.

If you have more than one AeroPoint in your survey, you can select which are used as ground control points (GCPs) and which are used as checkpoints to validate the model’s accuracy. 

For larger sites (>150 acres, or about 60 hectares), we recommend using at least three AeroPoints as GCPs.

4. If you’re using the controller to plan your mission, tap 

  • Plan

  • 2D Photogrammetry (for most sites) 

For linear missions, such as corridor surveys, tap Plan, followed by Linear Flight Mission.

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

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

You must drop at least three to produce a survey area.

To move a pin, tap on it again to select it, then either use the wheel on the right or drag it around with your finger. 

You can also delete the selected pin by tapping the trash icon.

7. Display and adjust the mission settings by tapping the white tab with arrows on the right.

 

Small area to cover?

  • Make sure that your mission/each battery lasts at least 10 minutes. 
  • Reduce speed, increase overlap, or

  • pause the mission towards the end of the mission.

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Before leaving the office: Settings

Setting Set to Question to ask yourself Reason
Height

260–400 feet (80 - 120 m)

How high should I fly compared to the take-off point?

The height is a balance between how fast you would like to complete the survey (higher makes it faster) and the ground sampling distance that you need (lower makes it better). This range satisfies this balance.

Speed *Max Speed Allowable How fast should I fly?

*Unless you’re trying to reach the required 10min flight time, increase speed to minimize the overall flight time. In low light conditions, reduce the speed and the shutter speed to ~1/800.

Shooting Mode 

Distance Shooting

What metric is used to capture images?

Distance shooting allows the drone to capture images with consistent overlap.

Finish 

Return To Home

What should I do after completing the mission?

Safety and not losing your drone. 

Once completed, the drone will go back to the home point automatically.

Go to Camera Settings

Photo Ratio

3:2

How much of the image should I delete?

3:2 deletes nothing, utilizing the whole sensor.

Everything else deletes data.

White Balance

Set to the conditions of the day.

What conditions should I accommodate?

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.

Gimbal Angle 

-90

Where should the camera point while flying?

All good surveys are built from images facing directly down (nadir). 

These can then be complemented by angled shots (obliques).

-90 is facing straight down, and 0 is horizontal facing the drone's flying direction.

Shutter Priority  

Enabled ~ 1000

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 aperture and ISO.

1000 is usually a good place to start for sunny conditions.

In low light conditions, reduce the shutter speed to ~800 and the speed.

Distortion Correction 

Disabled

Should the camera apply the distortion correction?

Leaving the distortion correction off allows the photogrammetric software to undistort the images. The software usually does a better job of this.

For any non-surveying purposes, leave it enabled.

Advanced settings (under Camera Settings button)

Side and Forward Overlapping Rate (%)

~75%

How much should each of the images overlap?

This provides enough overlap for some images to be 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 survey, you can reduce the horizontal overlap (no lower than 60%) to increase the area you can cover per battery.

Margin 

MANUAL 0

How much margin do you want to leave around the survey area?

You don't need any margin if you have covered the entire area you would like to survey accurately.

Course Angle

Adjust the flight direction with the yellow pin.

What direction should I fly to cover the survey area?

Fewer turns mean more flight time per battery.

The yellow pin on the screen can adjust the course angle after the flight plans have been produced. 

For linear/narrow surveys, use the Linear Flight Planning mode instead of 2D Photogrammetry.

 

  Onsite: Ground Control Placement

Lay out ground control and checkpoints. If you are using AeroPoints, we recommend laying them out before conducting your preflight checks.
  • Ensure you have placed your AeroPoint(s) at least five minutes before you start flying. 
  • If you do not have a known point on site, you must leave the AeroPoint 2 on for at least 10 minutes. If you are using AeroPoint 1s or a mixed fleet, they must be on for at least 45 minutes.
  • Do not turn off the AeroPoint before you finish flying.
Proper AeroPoint placement reminder
  • A clear view of the sky in all directions. Avoid power lines, walls, and trees.
  • To be on a relatively flat surface with a maximum of 20° from horizontal.
  • To remain unmoved during data capture. Avoid areas with foot traffic, if possible.
  • To be turned on to collect data. A solid green light will show next to “Logging” when on (applicable for AeroPoint 2 only). 
  • Record where you have put each AeroPoint, so they can be easily recovered at the end of the survey flight.

If you need to place an AeroPoint on a known point

  • Place the AeroPoint stencil precisely over the known point.
  • Spray-paint the corners.
  • Place the AeroPoint on top of the painted stencil.

 

  Onsite: Preflight Checks

  • Check that the batteries for the drone and controller are fully charged.
  • While the drone is off, ensure that the propellers aren’t damaged and that the frame arms are unfolded.
  • Check that a suitable SD card is securely inserted into the drone. Regularly format the card through the DJI Pilot App.
  • Remove the plastic and foam gimbal braces.
  • Place the drone in an unobstructed, flat area. No obstacles should be above or near the drone, and no traffic in the landing area at any time.
  • Turn on the controller and the drone. Always power the drone on after the controller.
  • Calibrate the compass if prompted to do so.

Tip: Ensure you are far from metal objects or magnets.

  • Ensure the home position is right by tapping Fly, followed by the map in the bottom left.
  • If you turned the drone on indoors or under anything, reset the home location by tapping on the menu in the top right-hand corner.
  • Send the mission to the drone by tapping the page icon on the left-hand side, then selecting from the Plan or KML File menu.
  • Check the settings and that they match the conditions of the day.
  • Activate any airspace certificates you have unlocked through Aircraft Settings (3 white dots on Top Right) and GeoZone Unlocking.

 Onsite: Flying the Drone

  • Confirm that the drone is ready by checking the status bar.
  • Start the mission.
    • Tap Invoke followed by Start. A checklist will come up, and ask for your confirmation before launching.

  • Check for any obstructions or low flying aircraft.
  • If it’s safe to take off, start the mission.

Tip: If you need to pause your mission, you can quickly change the mode switch from P-F. The mission can then be resumed from the GS RTK app.

 

  Onsite: Post Flight Checks

  • Turn off the drone and remove the batteries. The batteries will be warm but should not show signs of puffing or excessive heat.
  • Reattach the plastic gimbal bracket
  • Remove the SD card from the drone.
  • Check the image quality if possible.
    • Open a couple of the images to ensure they are sharp and clear and not over- or underexposed.
  • Ensure that your images cover the desired area and that no major issues are detected.

Please refer to this tutorial for more detailed information on uploading images from your Mavic 3 Enterprise to the Propeller Platform.


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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