Abstract
The Gaofen-7 (GF-7) satellite is equipped with two area array sensor footprint cameras to capture the laser altimeter spot. In order to establish a direct correspondence between the laser data and the stereo image data, a new method is proposed to fit the center of the spot using the brightness difference between the spot image and the footprint image. First, the geometric registration between the spot image and the footprint image is completed based on feature matching or template matching. Then, the brightness values between the two images are extracted from the corresponding image position to form a measurement, and the least squares adjustment method is used to calculate the parameters of the brightness conversion model between the spot image and the footprint image. Finally, according to the registration relationship, the center of the identified spots is respectively positioned in the footprint images, so that the laser spots are accurately identified in the along-track stereo footprint images. The experimental results show that the spot error of this method is less than 0.7 pixel, which has higher reliability and stability, and can be used for a GF-7 satellite footprint camera.
Highlights
The geometrical positioning accuracy of surveying and mapping satellites is mainly limited by the attitude performance of the satellite platform which affects the precision of orientation parameters [1].Due to the base-to-height ratio, platform stability, and other factors, the vertical accuracy of optical stereoscopic mapping is difficult to meet application requirements [2]
We propose a method that first completes the geometric registration between the spot image and the footprint image, combines the brightness difference of the corresponding pixels to adaptively calculate the conversion model parameters and obtain the spot center position based on the results
A schematic diagram showing the installation of the laser altimeter and the footprint camera of GF-7 is illustrated in Figure 1, wherein the pointing of the laser altimeter is substantially parallel to the visual axis of the footprint camera
Summary
The geometrical positioning accuracy of surveying and mapping satellites is mainly limited by the attitude performance of the satellite platform which affects the precision of orientation parameters [1].Due to the base-to-height ratio, platform stability, and other factors, the vertical accuracy of optical stereoscopic mapping is difficult to meet application requirements [2]. The geometrical positioning accuracy of surveying and mapping satellites is mainly limited by the attitude performance of the satellite platform which affects the precision of orientation parameters [1]. Integrating the stereo imagery and laser altimeter data has the potential to generate better geometrical positioning accuracy [3], especially for areas where it is difficult to obtain ground control points. Non-conjugated points are generated by back-projecting the laser ground points to the stereo images [3]. These deviations have caused great difficulties in constructing a combined adjustment model of laser data and stereo image data. 295 covering the XinJiang areas areas in China were were collected. 95 of effective three-exposure data data was collected in orbit
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