Works with Propeller PPK is a vendor-agnostic format that aircraft vendors can implement for out of the box compatibility with Propeller PPK.

An example data set is available here.

• Clarify roll / pitch / yaw coordinate frame

• Initial version of specification

Captured data is stored into one directory per flight. Each flight directory contains:

• 1 JPEG file for each image captured
• 1 RINEX format GNSS observation file covering the full period from takeoff to landing
• 1 flight metadata CSV file containing GNSS timestamps and additional metadata for each image

Each file in the flight directory is prefixed with the flight directory name so the mapping is not lost if flight folders are merged. This prefix can be any string, but we suggest a sequential ordering.

Propeller PPK will validate that each flight directory uploaded meets the following requirements

Flights/
    Flight01/
        Flight01_0001.JPG
        Flight01_0002.JPG
        Flight01_0003.JPG
        ...
        Flight01_GNSS.obs
        Flight01_metadata.csv
    Flight02/
        Flight02_0001.JPG
        Flight02_0002.JPG
        Flight02_0003.JPG
        ...
        Flight02_GNSS.obs
        Flight02_metadata.csv
    Flight03/
        Flight03_0001.JPG
        Flight03_0002.JPG
        Flight03_0003.JPG
        ...
        Flight03_GNSS.obs
        Flight03_metadata.csv

Images should captured at the native sensor resolution and aspect ratio without any cropping and saved in JPEG format. Images must be at least 12-megapixels.

Images must be named with the flight prefix and a unique (within the flight) 4 digit incrementing number and end in the .JPG extension, e.g. Flight01_0123.JPG.

Propeller PPK uses the following EXIF headers. Other headers are permitted and will be ignored.

Propeller PPK will validate that each flight directory uploaded meets the following requirements

GNSS observation data for each flight must be stored in RINEX version 3.04 format. The GNSS observations must:

• Cover the period from aircraft take off to landing
• Have no gaps between epochs of > 1 second
• Have a constant sample rate of 5 - 20 Hz
• Include signals for:
  • GPS L1
  • GPS L2
  • GLONASS L1
  • GLONASS L2
  • Galileo E1
  • Galileo E5

Other signals can be included and may be used in future but will be ignored otherwise.

To ensure accurate GNSS solutions every epoch must contain at least 16 GPS, GLONASS and Galileo satellites. With dual-band measurements with a signal-to-noise ratio (SNR) of > 35 dBHz. It is acceptable to have an initialisation window of up to 60 seconds at the beginning of the file that does not meet these requirements.

RINEX files must contain at least 2 minutes of observations after initialisation when processed using an AeroPoint 2 as the GNSS reference or 10 minutes when processed using the Propeller Corrections Network or an AeroPoint 1.

Propeller PPK uses the following RINEX headers. Other headers allowed by the RINEX specification are permitted and will be ignored.

Propeller PPK will validate that each RINEX file uploaded meets the following requirements

The flight metadata file contains additional information required to map each image to a PPK coordinate, as well as some aircraft specific metadata used to validate the uploaded data.

Each flight metadata file must be stored in Microsoft Excel style CSV format with:

• File encoding: UTF-8
• Field delimiter: ,
• Line ending: \r\n
• Quote character: "
• All string fields may contain up to 255 characters of valid Unicode

Manufacturer,Propeller
Model,DemoUAV
Serial number,AJ34NF12
Firmware version,1.75.24a_rev2
Propeller PPK version,1.0
Image,Timestamp (s),GPS week number,Antenna offset north (m),Antenna offset east (m),Antenna offset up (m),Roll (degrees),Pitch (degrees),Yaw (degrees),Approximate Longitude (degrees),Approximate Latitude (degrees),Approximate altitude (m)
Flight01_0001.JPG,105277.650307,2192,0.025,-0.030,0.190,0.00,-90.00,94.20,146.64916670,-35.85037326,280.124
Flight01_0002.JPG,105281.932945,2192,0.011,-0.018,0.193,0.00,-90.00,98.70,146.64947564,-35.85041480,280.044
Flight01_0003.JPG,105284.443190,2192,0.004,-0.003,0.195,0.00,-90.00,98.70,146.64975396,-35.85045122,280.071
...

The file is comprised of:

1. A header section, containing flight / aircraft specific information
2. A body containing image specific information

Headers must be encoded in Microsoft Excel style with:

• Fields containing , wrapped in " quotes
• " characters in fields encoded as ""

For example the field a string containing , and " should be encoded as "a string containing , and """

The body section must start with the static header row

Image,Timestamp (s),GPS week number,Antenna offset north (m),Antenna offset east (m),Antenna offset up (m),Roll (degrees),Pitch (degrees),Yaw (degrees),Approximate longitude (degrees),Approximate latitude (degrees),Approximate altitude (m)

This is used to delimit the header and body sections and give human-readable context.

The body section must contain one entry for every image captured.

The image focal plane to GNSS antenna phase center offset components are measured relative to the global ENU coordinate frame where:

• Antenna offset north (m) is positive when the GNSS antenna phase center is more north than the image focal plane
• Antenna offset east (m) is positive when the GNSS antenna phase center is more east than the image focal plane
• Antenna offset up (m) is positive when the GNSS antenna phase center is above the image focal plane

The GNSS antenna to image focal plane offset north / east / up components should be calculated using a lever-arm given the aircraft's geometry and roll / pitch / yaw values for each image.

If this is not possible and roll / pitch values are typically small (< 5 degrees) and the image sensor is mounted directly below the GNSS antenna a constant vertical offset may be supplied for the Antenna offset fields.

Propeller PPK will validate that each RINEX file uploaded meets the following requirements