Capturing images with the camera pointed exactly 90 degrees downward, or at nadir, is crucial for minimizing distortion and ensuring the highest quality data. In this blog post, we’ll explore the importance of maintaining a nadir camera angle, tips for achieving this both with and without software flight assistance, and strategies for reducing distortion when turning the drone.

The importance of a nadir camera angle

Keeping your drone camera at nadir is essential for several reasons:

  1. Minimal distortion: When the camera is pointed straight down, the resulting images have minimal geometric distortion, making them easier to stitch together into accurate orthomosaics and 3D models.
  2. Consistent data quality: Maintaining a consistent nadir angle ensures that your images have uniform scale and resolution across the entire mapping area, facilitating analysis and comparison.
  3. Reduced post-processing time: Images captured at nadir require less post-processing to correct for distortion, saving you time and effort in the data analysis phase.

Tips for maintaining a nadir camera angle

  1. Use a gimbal: Most modern mapping drones come equipped with a 3-axis gimbal, which helps to stabilize the camera and maintain a consistent angle. Ensure that your gimbal is properly calibrated and functioning correctly before each flight.
  2. Set the camera angle in your mission planning app: Many mission planning apps, such as DJI GS Pro and Pix4D Capture, allow you to set the desired camera angle for your mapping mission. By default, this should be set to 90 degrees (nadir) for most mapping applications.
  3. Fly in calm conditions: Strong winds or turbulence can cause the drone to tilt or roll, affecting the camera angle. Whenever possible, fly in calm weather conditions to minimize this effect.
  4. Maintain a consistent altitude: Flying at a consistent altitude helps to ensure that your camera remains at nadir throughout the mission. Use your drone’s altitude hold function or a mission planning app with terrain following to maintain a constant height above the ground.
  5. Use a nadir sensor: Some specialized mapping drones, such as the senseFly eBee X, come equipped with a nadir sensor that automatically detects and corrects for any deviations from the nadir position.

Minimizing distortion when turning the drone

Even with a nadir camera angle, turning the drone can introduce some distortion into your images. Here are some strategies for minimizing this effect:

  1. Use a mission planning app with automatic turns: Many mission planning apps can automatically calculate smooth, wide turns between flight lines to minimize the impact on image quality. This feature is sometimes called “terrain-aware turns” or “optimized turns.”
  2. Increase the overlap between flight lines: By increasing the side overlap between adjacent flight lines (e.g., to 70% or more), you can ensure that any distorted images captured during turns are compensated for by the surrounding overlapping images.
  3. Fly longer flight lines: Where possible, plan your mission with longer flight lines and fewer turns. This reduces the number of images captured during turns and minimizes the overall impact of turn-related distortion.
  4. Pause image capture during turns: Some drones and mission planning apps allow you to automatically pause image capture during turns. By not capturing images during these maneuvers, you can eliminate the most severely distorted photos from your dataset.

Managing nadir angle with and without software flight assistance

If your drone and mission planning app support autonomous flight, maintaining a nadir camera angle is relatively straightforward. Simply set the desired camera angle in the app, and the drone will automatically adjust the gimbal to maintain this angle throughout the flight.

However, if you’re flying manually or using a drone without autonomous capabilities, you’ll need to take a more hands-on approach:

  1. Adjust the gimbal manually: Use your drone’s manual gimbal controls to set the camera to a 90-degree angle before takeoff. Monitor the camera feed throughout the flight and make adjustments as necessary to maintain nadir.
  2. Fly smoothly and avoid sudden movements: Sudden changes in pitch, roll, or yaw can cause the camera to deviate from nadir. Fly smoothly and deliberately, avoiding jerky or abrupt maneuvers.
  3. Use a visual reference: If your drone has a live video feed, use the on-screen grid or a piece of tape on your screen as a visual reference to help keep the horizon level and the camera at nadir.
  4. Practice in a safe environment: Before attempting a mapping mission with manual flight, practice maintaining a nadir camera angle in a safe, open area. Develop a feel for the controls and how the drone responds to wind and other environmental factors.

Whether flying autonomously or manually, keeping your camera at nadir is a critical skill for any drone mapping scientist.

The good news is, as long as you’re out there in the field learning the skill, at least you’re not at a desk–it takes a lot to make a bad day spent outside flying a drone around. 🙂

Want more tips and a complete guide on how to plan and execute a drone mapping mission? We’ve got you.