In-Flight Geometric Calibration For Formosat-8 Frame Sensor Using Preflight Simulated Images

Tee-Ann Teo, TSUNG-HAN WEN, K.H HSU, M.C WU, Y.S LEE

Research output: Contribution to conferencePaperpeer-review

Abstract

The geometric quality of direct georeferencing relies on high-quality geometric calibration. In addition, in-flight geometric calibration plays an important role in refining the laboratory calibration parameters. This study aims to develop an in-flight geometric calibration method using pre-flight simulated Formosat-8 (FS8) satellite images. The proposed in-flight geometric calibration methods include (1) refinement of focal length and principal points in focal plane; (2) estimation of instrument biases between instrument orientation and AOCS (Attitude and Orbit Control Subsystem) reference frame. The pre-flight simulated FS8 frame images are a set of sequential images. The simulation sampling rate is 12 frames per second and the total number is 721 images. These highly overlapped simulated images generate a large number of tie points by image matching technique.
The ground control points and independent check points are simulated by orbital and attitude data from satellite metadata. This study utilizes photogrammetric bundle adjustment as a core technique in geometric calibration. In the refinement of focal length and principal points, self-calibration bundle adjustment is used to calculate the refined focal length and principal points from tie points between images. The experimental results showed that, the relative accuracies of focal length and principal points reached 1/1200 and 1/120, respectively. As the fieldof-view (FOV) of FS8 frame sensor is small than 1degree. The relative accuracies were relatively larger than normal angle frame camera (e.g., FOV > 50deg). In estimating instrument biases, calibration bundle adjustment with tie-points and control points is utilized to solve camera orientation parameters. The instrument biases are determined from the solved camera orientations and the orientation from AOCS. The experimental results showed that, the accuracies of calculated instrument biases reached 1pixels accuracy on ground. In summary, this study developed in-flight geometric calibration method for FS8 frame sensor using preflight simulated images. The proposed method can be deployed to FS8 geometric calibration operation system.
Original languageEnglish
StatePublished - Nov 2021
EventInternational Conference on Astronautics and Space Exploration(iCASE) - Hsinchu, Taiwan
Duration: 16 Nov 202118 Nov 2021
https://www.nspo.narl.org.tw/activity/iCASE/2021/

Conference

ConferenceInternational Conference on Astronautics and Space Exploration(iCASE)
Country/TerritoryTaiwan
CityHsinchu
Period16/11/2118/11/21
Internet address

Keywords

  • Formosat-8
  • frame sensor
  • geometric calibration
  • instrument biases
  • bundle adjustment

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