Feature extraction is an important step in image feature matching. And the repeatability of features is particularly crucial. The perspective deformation of images can decrease the repeatability of features. This paper introduces a feature extraction method which can improve the repeatability of features when notable perspective deformation exists. First, initial feature points are extracted by the classical Harris algorithm. Then a local support region is extracted for every initial feature point. Affine rectification parameters can be calculated based on the shape of the support region. Then the image patch around a feature point is resampled using these affine rectification parameters. The final feature points are extracted and described on the resampled image patches. The repeatability of the final features is much better than initial features thanks to the affine rectification. And the feature descriptors obtained on the resampled image patches are better to be used in image matching.
As an advanced technology, satellite remote sensing has been applied in a variety of fields and has brought numerous social benefits. This paper introduces a new operational satellite imagery processing system and conducts a case study using it by processing ZY-02C and ZY-3 satellite imagery. By way of this case study, this paper proposes a workflow involving the key generation technologies with fully automatic generation of advanced remote sensing products, such as the digital elevation model (DEM), the digital orthophoto map (DOM), and the high-resolution color-fused image. The proposed workflow in this system tackles the key practical issues related to the domestic satellite imagery process, such as low processing efficiency, low utilization, poor integration, etc. This system utilizes the following key generation technologies: automatic registration between the satellite imagery and the existing multi-geographic data, strip aerial triangulation of three-line array satellite images, multi-sensor image registration and fusion, dense matching of photogrammetric point clouds, and automatic correct splicing of wide range images. The proposed process system consists of two parts. The first part is the creation of a geographic information production mode with no manual intervention. This mode aims to improve the accuracy and efficiency of mass domestic satellite images to produce highly precise orientation by using global public basic geographic information databases like Map World, Google Earth, etc. The second part is the design of a workflow to ensure the stability of the production time and quality of domestic satellite imagery's advance product generation. Finally, this paper also discusses the accuracy of the process of image orientation and the precision of advanced products such as high-resolution color-fused image (ZY-02C), DEM (ZY-3), and DOM (ZY-3). The results show that the products of the proposed process system meet the requirements in both efficiency and quality, and the proposed process system is ready for future real-time domestic remote satellite imagery generation.
For the purpose of improving the efficiency of GIS data-updating over urban areas, a new approach of aerial
triangulation (AT) with ground control points auto extracted from the existing AT results is introduced in the paper. The
existing AT results mean the existing aerial imagery with interior and exterior orientation parameters. Through a multi-views
image matching between the new aerial photos and old photos, enormous ground control points could be auto
extracted and their ground coordinates could be calculated by the forward-intersecting of old aerial photos. The
efficiency and accuracy of the method have been tested and analysed with several actual aerial imagery blocks. The
experiment results presented in this paper shows that the method could not only extract enormous GCPs automatically
which lead to a greatly improvement of the efficiency of AT over urban areas, but also achieve the same level of
accuracy of the old AT results.
A new ortho updating method by means of the aerial triangulation which Ground Control Points (GCPs) are auto
matched from the existing ortho photos and DEM has been introduced in the paper. In this new method, a two steps automatching
arithmetic have been used: the one is used in auto matching between the adjacent aerial photos in order to auto
transferring tie points of the block; the other is used to matching the tie points with the existing ortho photos by the aid of
DEM, if the matching succeed, the ground coordinates of the tie points could be obtained and then it could be used as a
GCP in the aerial triangulation. Therefore, the ortho updating method presented in the paper could not only extract tie
points, but also could extract enormous GCPs to calculate the Exterior Orientation parameters (EOP) of the aerial images
with high accuracy and high reliability.