In‐orbit geometric calibration and validation of ZY‐3 three‐line cameras based on CCD‐detector look angles

Abstract

A simple and feasible orientation method for the three-line cameras of the ZiYuan-3 (ZY-3) satellite is introduced. The method calibrates the CCD-detector look angles in the attitude determination reference (ADR) coordinate system rather than modifying the laboratory-calibrated orientation parameters, which are not necessary for the geometric calibration. Additionally, the unknown parameters of the model are virtually uncorrelated. Experimental results show that the direct georeferencing accuracy of ZY-3 nadir images have been improved from the kilometre level to better than 9 m in planimetry, and that of the forward-andbackward stereopair was also raised to better than 18 m in plan and 4 m in height. After a bundle adjustment using four ground control points, a higher accuracy of about 3Á4 m in plan and 1Á6 m in height was achieved.

Geometric Calibration of Ziyuan-3 Three-Line Cameras Combining Ground Control Points and Lines

“…In this paper, the point-based geometric calibration model established by Cao et al (2015) is employed and used. Based on the point-based geometric calibration model, the line-based geometric calibration model of the ZY-3 TLCs is established.…”

Geometric Calibration of Ziyuan-3 Three-Line Cameras Combining Ground Control Points and Lines

“…It is very difficult and even impossible to calibrate the look angles of each CCD detector, since a very large number of ground controls are necessary. For this reason, the look-angle model in Cao et al (2015) is used in the actual procedure of the geometric calibration of the ZY-3 TLCs. The mathematical expression of the model is as follows: (1) For each GCP, according to Equations 3 and 8, two error equations are established by using the image-space and objectspace coordinates of the GCP.…”

“…The base-to-height ratio formed by the FWD and BWD cameras is about 0.8. Similarly, serval feasible and effective geometric calibration approaches for the ZY-3 TLCs were developed, as referred in (Cao et al, 2015;Chen et al, 2015;Wang et al, 2014;G. Zhang et al, 2014;.…”

“…However, these orientation parameters have very strong correlations between each other, so that it is very difficult to separate them. In order to avoid the strong correlations in the geometric calibration of the ZY-3 TLCs, Cao et al (2015) used the CCD-detector look angles in the attitude determination reference coordinate system to describe the comprehensive effects of the orientation parameters   …”

Improve the Zy-3 Height Accuracy Using Icesat/Glas Laser Altimeter Data

“…D'Angelo (2013) evaluated the ZY-3 performance for DSM and orthophoto generation on two scenes east of Munich, and the overall RMSE between ZY-3 DSM and LIDAR reference is 2.0 m. Tang et al(2015) evaluated the overall vertical RMSE of DSM without GCPs was 5.56m. Cao et al (2015) examined the geometric calibration and validation of the ZY-3's CCD linear array sensors. Although ZY-3 has very high accuracy for direct geo-locations without GCPs (Ground Control Points), use of some GCPs is still indispensible for high precise stereo mapping, especially in order to improve the elevation accuracy.…”