Abstract
Abstract. At 48 years of age CORONA-KH-4B images are important for actual urban planning in Bangladesh, where no old maps or aerial images exist, indicating locations of former water courses that are no longer visible, but causing problems for the stability of building ground.CORONA KH-4B images are available for very low cost or even free of charge. A forward and a backward-looking panoramic camera with a nadir angle of approximately 15° enabled a stereoscopic coverage. Taken from a height of 154km, an image covers approximately 220km × 14km up to 17km with a height to base relation of 1:1.85. The ground sampling distance (GSD) varies with the incidence angle from 1.77m in the centre of the image up to 2.18m in Y-direction and 2.69m in the X-direction at the ends of the images. These nice conditions of the old images are affected by geometric problems of the panoramic images. A geometric bending can be improved by a correction based on the available sidelines, nevertheless deformations dominantly in the longitudinal direction only can be determined based on ground control points. A group of neighboured images have similar deformations, allowing the determination of a correction grid, describing the systematic image errors. This improved the geometry strongly, but could not eliminate all individual and local geometric problems. The high morphologic quality of the CORONA images, but limited absolute height accuracy has been improved by merging with the highly accurate TDM90 height model. For ortho images a fitting of neighboured images was required.
Highlights
The required geometric handling of the declassified panchromatic CORONA images, which can be downloaded from the USGS Earth Explorer, is poorly described in the literature due to the priority of CORONA for reconnaissance and not for the generation of height models and ortho images. (Schneider et al 2001) and (Dowman et al 2012) explain the method for using a part of the CORONA image, but no literature is available for the precise handling of the full images. (Auelmann 2015) gives detailed information about the configuration and imaging condition of the CORONA satellite
ground control points (GCPs) have been extracted from Google Earth which has at least a relative accuracy of ~ 1.5m
CORONA images are optimal for the reconstruction of the situation 48 years ago for which at least in Bangladesh has no geo-referenced information as base of urban planning to avoid unstable building ground
Summary
The required geometric handling of the declassified panchromatic CORONA images, which can be downloaded from the USGS Earth Explorer, is poorly described in the literature due to the priority of CORONA for reconnaissance and not for the generation of height models and ortho images. (Schneider et al 2001) and (Dowman et al 2012) explain the method for using a part of the CORONA image, but no literature is available for the precise handling of the full images. (Auelmann 2015) gives detailed information about the configuration and imaging condition of the CORONA satellite. In addition the standard image overlap in flight direction of CORONA is limited to 6% in the centre and 20% at the end of images (figure 2), and dynamic imaging with a rotating optics causes systematic errors that may change from image to image. It is difficult to identify GCPs in images with a time difference of 48 years This causes bigger problems than the accuracy of Google Earth. The required geometric transformations and the method of determining the systematic errors are described, as well as the improvement of generated height models and the remaining part of the systematic image. The double-blind peer-review was conducted on the basis of the full paper
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