At Google, Ceres is used to:
Matterport, uses Ceres for global alignment of 3D point clouds and for pose graph optimization.
The Autonomous Systems Lab at ETH Zurich uses Ceres for
Camera and Camera/IMU Calibration.
Large scale optimization of visual, inertial, gps and wheel-odometry data for long term autonomy.
OpenPTrack uses Ceres for camera calibration.
The Intelligent Autonomous System Lab at University of Padova, Italy, uses Ceres for
Camera/depth sensors network calibration.
Depth sensor distortion map estimation.
The Applied Research Laboratory at Pennsylvania State University uses in their synthetic aperture Sonar beamforming engine, called ASASIN , for estimating platform kinematics.
Colmap is an open source structure from motion library that makes heavy use of Ceres for bundle adjustment with support for many camera models and for other non-linear least-squares problems (relative, absolute pose refinement, etc.).