Georeferencing of close range photogrammetric data

Abstract

The paper presents some general approaches for indirect georeferencing of close range photogrammetric data being acquired for various applications by the imaging systems of different types either independently or in integration. Various digital metric or non-metric cameras and terrestrial laser scanning systems, which register the objects to determine their shape and location, can be located either on the MMS moved vehicles or on the terrestrial stable stands. Various factors, such as objects’ location, dimension and shape as well as the form of data required and type of the photogrammetric imaging systems have the major effect on the approach to be used for georeferencing of photogrammetric data. In case of dynamic collection of imaging data, direct georeferencing is required. In this case, the GPS/INS systems of adequate accuracy for direct georeferencing of registered data, have to be ensured. Such systems allow to orient all collected data (cloud of points or discrete points for the objects) in the uniform coordinate system which can be later re-transformed to the final reference system in post processing stage. In case of imaging by the conventional metric or non-metric cameras located on the terrestrial stable stands, indirect georeferencing of data is usually executed in the post-processing stage. In many of close range applications, data collected by one or more photogrammetric acquisition systems located in various positions around the object, are integrated. This requires determination of orientation of all sets of photogrammetric data in the same reference system, which for close range applications is usually arbitrary selected. The indirect georeferencing approaches of close range imagery data require always a few control data, mostly points, either for a block of images or for each separate image/model. The methods are classified into two general groups: (1) multi-image exterior orientation, including self calibration, for orientation of images of similar or different scale and geometry taken by the metric and/or non metric cameras, in simultaneous adjustment of all photogrammetric data, and (2) the sequential. orientation of each image or model. The spatial location of control data for orientation of the block or separate model / image is determined either by the field survey or from the set of data already georeferenced, which were collected earlier by close range photogrammetric methods. In this paper, some approaches of indirect georeferencing of photogrammetric data for the selected objects, obtained only from imagery taken by metric and nonmetric cameras or in integration with data from terrestrial laser scanning, are presented