Open Photogrammetry Format (OPF) Specification

Primary Authors: Grégoire Krähenbühl, Klaus Schneider-Zapp, Bastien Dalla Piazza, Juan Hernando, Juan Palacios, Massimiliano Bellomo, Mohamed-Ghaïth Kaabi, Christoph Strecha

Welcome to the OPF Specification! Here you will find the official documentation and resources for the Open Photogrammetry Format (OPF).

What is OPF?

OPF is the specification for a standardized file format designed for photogrammetry data. The specification is open and free and aims at making it easy to store, exchange, and collaborate on photogrammetric data between different parties and software products. Typically, a project is made of a “project container” file (.opf) which references the other project components, such as the files storing the camera parameters or point clouds.

Features

  • Based as much as possible on simple human readable JSON files, leverage efficient binary formats where a text-based representation would be impractical (for example for the point cloud data)

  • OPF organizes photogrammetry data in a structured manner, allowing for easy access and retrieval of information.

  • The data model includes information on both input and output of the photogrametry process:

    • The input data include information about input cameras (camera list, input camera parameters), coordinate reference system, control points, scale and orientation constraints, etc.

    • The output data include information about camera calibration (sparse point cloud, calibrated cameras) and the dense reconstructed point clouds.

  • Efficient Storage of point clouds: The point cloud format for ATPs (sparse point cloud) and dense point cloud included in this specification is based on the open standard GlTF and is designed to be memory-mappable and spatially partitioned, enabling both efficient processing and progressive rendering of massive point clouds. The format retains information on the point visibiliy on images, normals, custom attributes, and more.

  • Flexible Extension System: OPF is designed to be highly extensible and customizable, allowing for easy expansion of data representation as needed.

  • OPF will be improved on an on-going basis to support additional photogrammetric outputs.

  • OPF is a stable format: it has strict schema semantic versioning rules, giving strong compatibility guarantee and peace of mind for the implementers. JSON schemas are provided for validation.

Content of the specification

Existing tooling

We try to maintain here a non-comprehensive list of tools that implement the OPF specification. If you have a tool that implements OPF and you would like it to be listed here, please reach out to us!

Citation

If you use the OPF specification in your research or projects, we kindly request that you cite it as follows:

The Open Photogrammetry Format Specification, Grégoire Krähenbühl, Klaus Schneider-Zapp, Bastien Dalla Piazza, Juan Hernando, Juan Palacios, Massimiliano Bellomo, Mohamed-Ghaïth Kaabi, Christoph Strecha, Pix4D, 2023, retrived from https://pix4d.github.io/opf-spec/

License

Copyright (c) 2023 Pix4D SA

This specification, including but not limited to: all markdown files, json schemas and any automatically produced HTML and PDF files are licensed under the Creative Commons Attribution 4.0 International License (CC BY-SA 4.0).

All scripts and/or code contained in this repository are licensed under Apache License 2.0.

Third party documents or tools that are used or referred to in this specification are licensed under their own terms by their respective copyright owners.

Contact

If you have any questions, feedback, or suggestions regarding the OPF specification, please feel free to reach out to us or create an issue here: https://github.com/Pix4D/opf-spec/issues. We would love to hear from you! To report issues related to specific Pix4D product support, please reach out through Pix4D support pages https://support.pix4d.com/hc/en-us

Thank you for your interest in OPF! We hope it helps streamline and enhance your photogrammetry workflows.