EXPERIENCES WITH DIGITAL CAMERAS FOR EARTH OBSERVATION Dieter Fritsch Institute of Photogrammetry, University of Stuttgart, Keplerstrasse 11, D-70174 Stuttgart, Tel. +49,711,121,3386, Fax +49,711,121,3297, email: Dieter.Fritsch@ifp.uni-stuttgart.de Abstract The paper reviews the methods of digital imaging for photogrammetric purposes. Currently, two architectures compete with each other: the full frame CCD array and the linear array CCD. It seems, that in a long term the full frame will overcome the deficiencies of low spatial resolution and small image format. But it is no question that for the time being three-line imaging is the leading concept for Earth observation. Two systems will be presented which are based on this architecture. The Modular Opto-electronic Multispectral Stereo Scanner (MOMS) of 2nd generation was designed for Earth observation from space, and the Digital Photogrammetric Assembly (DPA) as an airborne digital imager. Both systems have been flown over some testsites, resulting experiences and results are presented. 1. INTRODUCTION Aerial photogrammetry and optical remote sensing is evolving from the exclusive use of film- based optical sensors to fully digital electro-optical and active electronic sensors with multispectral capabilities. These sensors can be roughly categorized as frame-based when large area charge couple devices (CCDs) are used for the imaging process, or as line scanners (pushbroom imagers) when several CCD line arrays are arranged in the focal plane of an optical camera system. It is out of question, that the frame-based digital data acquisition has some advantages over the pushbroom principle because of its stable geometry for the full image frame. In close range photogrammetry the use of digital still cameras automatically involves the frame- based approach. For this application, a great variety of digital cameras is offered by vendors of photographic equipment. The frame-based CCDs vary with resolutions of VGA standard (640x480 pixels - for instance the Apple Quick Take 150) to professional photographic systems (Kodak DCS200 and DCS420: 1524x1012 pixels, and the Kodak highest resolution portable digital camera DCS460: 3060x2036 pixels). The Kodak DCS200 was the first high resolution stillvideo camera on the market. It consists of a modified Nikon 8008s camera body with a 14 mm x 9 mm CCD sensor (Kodak KAF 1600, 1524 x 1012 pixels, 9 μm x 9 μm pixel size) in the imaging plane. The camera is offered alternatively with a B/W and color CCD sensor, respectively. Digital images can be stored on a 2 MB DRAM or optionally on a 80 MB internal harddisk, which offers storage capability for 50 uncompressed images. The digital images are transferred from the internal camera harddisk into a computer via a SCSI interface. To operate the DCS200 is equivalent to those functions of a modern automatic SLR camera. Experience using the DCS200 and DCS420 for photogrammetric close- range applications are given by C.S. Fraser et al. (1995) and A Grün et al. (1995). Relative accuracies well in excess of 1:100,000 were verified, with the precisions for combined networks