Collecting with DJI Drones
Collecting with DJI drones is fast and easy using the Hivemapper Studio mission planner. Follow these steps to get started flying and mapping anywhere in the world.
1. Enable Video Captions on your DJI deviceDJI drones are capable of recording GPS metadata alongside your video files that Hivemapper can use to help generate and georegister your maps. You can enable Video Captions from the camera settings menu in DJI GO.
Once enabled your drone will begin producing .SRT files alongside your video files or embed the GPS data directly into the video files. To confirm your drone is correctly recording this file you can open your video file in VLC Media Player and confirm the existence of a subtitle track.
2. Download Litchi flight controller app
Litchi is a mission planning app that allows users to plan missions and fly their drone autonomously. Hivemapper Studio will create custom mapping missions that can be executed using this app. Setup an account and download the mobile app on the device you use to control your DJI device.
3. Plan a mission using Hivemapper Studio
In Studio you can quickly navigate to any location on the planet and generate a custom mapping mission that can be flown with your DJI drone via the Litchi app.
To plan a mission go to studio.hivemapper.com and navigate to the area on the map you would like to map. You will see the world is divided up into tiles. Each tile covers .1 sq km’s and contains about 2 km of flightpath your drone will need to fly to complete it. You can select up to 6 tiles in a single mission or whatever your drone can complete in a single battery. Select your tiles and press Generate flight path.
Studio will then prompt you to set a launch point. Setting a precise launch point is required to safely use Litchi’s above ground feature. You can always move your launch point later, however selecting a launch point now will help studio generate the most efficient path for the area. Move your launch point marker to your predicted launch location and press Launch from here.
In addition to downloading a copy of the flight path to your computer, Studio will present you with a link to open the flightpath in Litchi. Open your flightpath in litchi. If you are satisfied with your mission be sure to save it to your own account so it can be located and opened on your mobile device.
When you arrive at your location connect your drone to your mobile device and load the mission in Litchi. Verify that you are located close to waypoint 1. Check for obstructions overhead and hit the play button when ready to execute the mission. Press RTH at any time to call the drone home or enter sport more to immediately regain control. When your drone completes the mission or reaches its low battery return home level the drone will safely return home.
How to Fly
Hivemapper intelligently searches your video for any usable frames, so when it comes to collection even random, unplanned missions have the ability to generate accurate maps. Here are some tips to help you get the most out of your collection:
1. Basic Concepts
Cover every surface from multiple angles. If a spot is not captured by the video from multiple perspectives, we can’t locate it in 3D space. Think of the camera’s field of view as a paintbrush, where strokes are required from multiple angles to get paint into all the little nooks and crannies of the ground.
Keep the camera angled down. Ignore everything you know about framing and shot composition. Hivemapper works by tracking objects and how they move in relation to each other. The sky has no tracking points and objects farther down the horizon will be too far away to accurately track.
Avoid quick rotations and hovering in place. - Remember - we need multiple perspectives and turning the camera in place does not do that. Instead fly forward while turning slowly or, for quicker turns, turn sideways while moving around a point of interest. Always keep moving for best results.
2. Height and framing
The altitude at which you should fly is determined by the 3D details which you hope to capture, your camera’s lens setup, and recording resolution. Below are a few examples of what your image should look like depending on what details you are trying to map. Examples are from a DJI Phantom 4 camera with a 24mm lens (35mm equivalent).
Wide - With this POV you will be able to map large structures like houses and large trees and bushes in detailed 3D. Items as small as cars will also appear in 3D and produce Change Detection results, however they will likely appear as simplified blobs or fused to neighboring objects making them harder to identify. You should not expect to find narrow objects like fences, utility poles, or minor changes in plant growth, mapped in 3D. This example was shot at 400ft AGL.
Medium - With this POV you will able to map most objects and structures at least a foot wide in 3D. That means, on buildings, you should see details like new solar panels or new AC equipment show up in Change Detection. You should be able to detect plant growth and stationary cars with a high degree of detail. Changes on the ground such as growing piles of dirt or excavation can also been seen at this level in relatively high detail. This example was shot at 280ft AGL.
Close - With this POV you can map even small objects, under a foot wide, in 3D. You should choose this level if you hope to map narrow objects like fences and utility poles. Random smaller objects like supplies or traffic cones can also be mapped as well as subtle changes like plant growth or terrain shifts. This example was shot at 150ft AGL.
Orbits are excellent for mapping a single object or area. Orbiting an object or area multiple times while shifting your altitude and orbit radius will yield even greater results. This type of collection is ideal and will generally produce the most detailed and reliable results. This collection pattern is also easily achievable at any altitude.
Just like mowing a lawn, the idea here is to cover every bit of ground with minimal overlap. A lawnmower style collection is best when you are trying to map large areas as efficiently as possible. If using DJI consumer drone’s we recommend reading more about this type of collection through our autonomous collection guide. A lawnmower flightpath is best suited to aircraft flying under 2000ft AGL.
GPS Metadata Support
Many video cameras produce metadata containing information about their location and camera settings. This metadata is helpful for building accurate maps. Hivemapper automatically extracts metadata from a wide variety of cameras. Video cameras produce this metadata in different formats.
Here is a list of our favorite drone cameras and their possible metadata formats:
|DJI||Mavic 2 Pro/Zoom|
|DJI||Mavic Air 2|
|AAI||Shadow 200 RQ-7B|
Hivemapper recommends using these camera settings for building maps:
Automatic Exposure - Most mapping locations will have considerable fluctuation in lighting; having both overexposed sunny areas to very dark shadowy areas. For that reason we recommend using automatic exposure to ensure all frames are correctly exposed. High shutter speeds are not an issue however shutter speeds below 1/50 may result in lower quality maps due to motion blur and should be avoided if possible.
Resolution/Frame-rate - Hivemapper samples a few frames a second so practically any video frame-rate gives Hivemapper more than enough data for a high quality reconstruction. Hivemapper can, however, use any additional resolution you can throw at it when processing in high quality mode. If your equipment offers a trade off between resolution and framerate we recommend favoring resolution.
Default (standard) picture profile - We recommend using your camera's standard picture profile. Hivemapper does not currently benefit from some of the more robust, flat pictures profiles like LOG or Cinema-D, etc. Any additional brightness or sharpening modifications should be disabled.
Format - Hivemapper works with any resolution using a modern video format including with Infrared video (IR.) If you experience any issues uploading a specific format please contact us at firstname.lastname@example.org.