Litchi Waypoint Mission to DJI Fly Hyperlapse Mission Converter Instructions BETA!!!

Instructions

This application will convert a Litchi waypoint mission into a DJI Fly hyperlapse JSON file.

In page one of Litchi Waypoint Mission to DJI Fly Hyperlapse Mission Converter:
1. Provide a name for this hyperlapse mission. If no name is provided, the basename of the input file will be used.
2. Set the time interval between photos. For fast-moving objects such as cars, use a small value of 1 or 2 seconds. For slow-moving objects such as clouds, use a larger value of 10 to 20 seconds.
3. Set the desired hyperlapse duration in seconds.
4. Enter the geoid height. This value may be obtained by entering the GPS coordinates of the mission into the Geoid Height Calculator. Since this value changes slowly over distance, this application will remember this value for future conversions.
5. Specify a Litchi CSV file to be converted.
6. Generate the hyperlapse mission and review the resulting parameters.
In page two of Litchi Waypoint Mission to DJI Fly Hyperlapse Mission Converter:
1. Review the displayed mission plot and mission data.
2. Download the ZIP file.
3. Uncompress the ZIP file to extract a hyperlapse mission folder.
On the device running DJI Fly:
1. Navigate to the hyperlapse folder.
2. Copy the created hyperlapse mission folder created by Litchi Waypoint Mission to DJI Fly Hyperlapse Mission Converter to the hyperlapse folder on the flying device running DJI Fly.
When ready to execute the hyperlapse mission in DJI Fly:
1. Select the hyperlapse function
2. Select the waypoints option
3. Open the hyperlapse mission created with this utility
4. Verify the hyperlapse mission parameters (such as interval and duration)
  - Each waypoint image will contain a waypoint number. Example: "Waypoint 3".
5. Start the hyperlapse

DJI Fly Hyperlapse

DJI Fly hyperlapse waypoint missions can be created and then saved on the flying device. One disadvantage of this process is that the hyperlapse mission must be created with the drone in the air. This web application enables the conversion of a Litchi waypoint mission (in CSV or KMZ format) into a DJI Fly hyperlapse mission stored in JSON format.

DJI Fly hyperlapse missions are stored in the "Hyperlapse" folder on the device running the DJI Fly application. Each hyperlapse mission is located in its only sub-folder and is comprised of a JSON file containing the mission parameters and two or more PNG image files that are displayed with each waypoint in DJI Fly.

This application produces a ZIP file that must be uncompressed. The contents of the ZIP archive can then be copied to the "Hyperlapse" folder of the flying device. Unlike regular waypoint missions, there is no need to create a "dummy" hyperlapse to be overwritten. The new hyperlaps mission can simply be dropped into place in the "Hyperlapse" folder.

See the notes below for important information about hyperlapse heights.

Notes

Hyperlapse Heights are a Problem
- The Mystery of DJI's Hyperlapse Altitude Date I have been unable to replicate DJI's target height in the JSON file when converting Litchi waypoints over to DJI's native Hyperlapse format. Getting the flight heights to match up has proven to be incredibly difficult, and I have been unable to identify an online source that matches DJI's altitude data. Instead of using the usual height-above-takeoff at each waypoint (which are stored in the JSON file), DJI's software appears to use a proprietary mix of GPS and onboard sensor data. DJI's algorithm has not been published and has proven to be difficult to reverse-engineer. The end result is that converted Litchi paths will consistently face vertical discrepancies, simply because I have not identified how DJI calculates the "altitude" value in the hyperlapse JSON data. If you would like to help, design and fly a native DJI hyperlapse mission. Then send me the original hyperlapse JSON file and either an AirData or PhantomHelp flight log so that I can analyze the data.
- My Best Approximation: For reasons that are unclear, the height of DJI hyperlapse missions are determined by an "altitude" value instead of the usual "height above take-off" value. I have been unable to identify exactly how that altitude value is calculated. The closest I have come is to calculate it as an offset to the height above the WGS84 ellipsoid. This height can be computed as the height AGL plus the orthometric height (Google elevation) plus the difference between the geoid height and the ellipsoid. In order to calculate this, a call to the Google elevation API is made and the geoid height must be provided. Fortunately, the geoid height can be queried on-line. Even with this calculation, the resulting drone height AGL may vary by a number of meters. Please use caution when flying a hyperlapse mission close to ground.
- Height Repeatability: The altitude of DJI Fly hyperlapse missions has been found to be inconsistent. For reasons that remain unclear, saved hyperlapse waypoint missions will sometimes/often fly at an altitude different (usually higher) from their originally intended height. This issue has been reported by multiple users, yet DJI has not formally acknowledged it. As a result, caution is strongly advised when re-flying saved hyperlapse missions, including those generated with this utility. More information is available.
It is unclear which DJI drones support this hyperlapse format. I know the newer drones such as the Mavic 3/4 series, the Air 3 series, and the Mini 4/5 Pro do. If you successfully use this utility for other drones, please let me know.
When creating a waypoint hyperlapse manually, DJI Fly imposes several undocumented constraints on the allowable distance and heading changes between waypoints. When creating a waypoint hyperlapce using this utility, those contstraints appear to be relaxed. Instead, DJI may silently adjust one or more parameters to make the mission execute.
It has been reported that when the hyperlapse mission is executed, a duplicate hyperlaps mission is created. I have not experienced this so it is unclear what may have caused that.