Method for determining the footprint center of a satellite laser altimeter based on marked waveforms by CCRs

Earth and Space Science

et al. 2020

The Gao Fen 7 (GF-7) satellite is China's first submeter, high-resolution Earth observation and remote sensing satellite for natural resource monitoring, land surveying, and other industrial applications in China. The GF-7 laser altimeter system is the successor of the ZiYuan3-02 (ZY3-02 satellite) laser altimeter. The key objective of the GF-7 laser altimetry system is to provide high-precision ground elevation control points that assist in optical imaging to achieve 1:10000 mapping in China. This paper introduces the GF-7 laser altimeter system payload specifications, mission objectives, in-orbit calibration plan, data products, and service policy. In the future, the GF-7 laser altimeter system will also serve multidisciplinary and professional applications through its precise elevation measurement capabilities. In addition, it will play a vital role in Earth observation, climate change monitoring, and environmental protection.

f ()(, x, y) = \sqrt{()(, x - a_{i}) + ()(, y - b_{i})} - r_{i}

where ( x , y ) is the laser footprint centroid coordinate, ( a i , b i ) is the i th CCR ground coordinates, and r i is the i th CCR energy radius.…”

Section: In‐orbit Calibrationmentioning

confidence: 99%

“…The least squares method is used to solve the optimal position of the laser footprint center. Then the coordinates of the optimal position are brought into the formula (1) to complete the GF-7 laser altimeter geometric calibration (Ma et al, 2018).…”

Section: In-orbit Geometry Calibration Based On Corner Cube Retroreflmentioning

confidence: 99%

Overview of the GF‐7 Laser Altimeter System Mission

Tang

Earth and Space Science

et al. 2020

“…5. According to the echo waveform of the triggered CCR, CCR ground coordinates, satellite orbit and attitude, atmosphere, tide, and other data, the geometric calibration based CCR is completed based on the calibration model [14], [15]. This field test is used to verify and analyze the laser echo energy and calibrate the ranging.…”

Section: B Laser Data Processing 1) Ranging Data Processingmentioning

confidence: 99%

Design and Data Processing of China's First Spaceborne Laser Altimeter System for Earth Observation: GaoFen-7

Guo-qin

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

et al. 2020

The GaoFen-7 (GF-7) satellite, which was launched on November 3, 2019, is China's first civilian submeter stereo mapping satellite. The satellite is equipped with the first laser altimeter officially in China for earth observation. Except for the laser altimeter, the GF-7 spaceborne laser altimeter system also includes two laser footprint cameras and a laser optical axis surveillance camera. The laser altimeter system is designed and used to assist improving the elevation accuracy without ground control points of the two line-array stereo mapping cameras. This article details the design of the GF-7 spaceborne laser altimeter system, its ranging performance in the laboratory, and its data processing method. The type of data products is also released. These data will play a vital role in the application of geography, glaciology, forestry, and other industries.

“…Airborne infrared camera imaging calibration require strict synchronous exposure of spaceborne laser and airborne camera , and can only be implemented at night when the moon is below the horizon (Magruder et al, 2010;Schutz, 2001). The CCR calibration method mainly relies on the waveform to extract the echo energy, and the atmosphere and reflectivity of ground objects will introduce errors (Ma et al, 2018;Magruder et al, 2006). The attitude-maneuver calibration method requires high-agility satellite platform, and will introduce additional high-frequency attitude noise (Luthcke et al, 2000;Luthcke et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Pointing Bias Calibration of Gaofen-7 Laser Altimeter Based on Single Laser Footprint Image

ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci.

et al. 2020

Abstract. The GaoFen-7 (GF-7) satellite is successfully launched on November 3, 2019, and its laser altimeter system is officially and firstly employed as the main payload for earth observations in China, which includes two sets of laser altimeters and laser footprint cameras. The Laser Footprint Image (LFI) is used to capture laser spots on the ground. In order to make up for the shortcomings of high cost field work for the traditional laser altimeter ground detector-based calibration method, this paper proposes a novel laser altimeter calibration method based on LFI. Firstly, the spaceborne laser calibration model and the Laser Footprint Camera (LFC) geolocation model are established. Secondly, the image coordinates of laser spot centroid are extracted from LFI, and the ground location of is obtained by ray intersecting with the reference Digital Surface Model (DSM). Finally, the centroid of laser spot is considered as Ground Control Point (GCP), and the pointing bias of GF-7 laser altimeter is calibrated by the Least Squares Estimation (LSE). The ALOS Global Digital Surface Model “ALOS World 3D-30m” (AW3D30) is used to evaluate the elevation accuracy of GF-7 laser altimeter before and after the calibration. The results indicate that elevation accuracy of the GF-7 laser altimeter is improved significantly after calibration. The proposed method can be effectively applied for high-frequency geometric calibration of GF-7 laser altimeter.