NATIONAL GUIDELINES FOR DIGITAL CAMERA SYSTEMS CERTIFICATION
Keywords: Mapping standards, camera calibration, accuracy guidelines, digital photogrammetric sensor, photogrammetric test field, radiometry, spatial resolution
Abstract. Digital camera systems are a key component in the production of reliable, geometrically accurate, high-resolution geospatial products. These systems have replaced film imaging in photogrammetric data capturing. Today, we see a proliferation of imaging sensors collecting photographs in different ground resolutions, spectral bands, swath sizes, radiometric characteristics, accuracies and carried on different mobile platforms. In addition, these imaging sensors are combined with navigational tools (such as GPS and IMU), active sensors such as laser scanning and powerful processing tools to obtain high quality geospatial products. The quality (accuracy, completeness, consistency, etc.) of these geospatial products is based on the use of calibrated, high-quality digital camera systems.
The new survey regulations of the state of Israel specify the quality requirements for each geospatial product including: maps at different scales and for different purposes, elevation models, orthophotographs, three-dimensional models at different levels of details (LOD) and more. In addition, the regulations require that digital camera systems used for mapping purposes should be certified using a rigorous mapping systems certification and validation process which is specified in the Director General Instructions. The Director General Instructions for digital camera systems certification specify a two-step process as follows:
1. Theoretical analysis of system components that includes: study of the accuracy of each component and an integrative error propagation evaluation, examination of the radiometric and spectral response curves for the imaging sensors, the calibration requirements, and the working procedures.
2. Empirical study of the digital mapping system that examines a typical project (product scale, flight height, number and configuration of ground control points and process). The study examine all the aspects of the final product including; its accuracy, the product pixels size on the ground (spatial resolution), its completeness (missing pixels and striping affect), its radiometric properties (e.g., relative edge response) and its spectral characteristics (e.g., histogram spread, bands misalignment).
This methodology was tested on a number of medium to large format digital cameras. The certification process is a basic stage in the mapping chain in Israel. This article provides the details of the Director General Instructions for digital camera systems certification, the methodology for certification and the tests that were carried out.