Error analysis of exterior orientation elements on geolocation for a Moon-based Earth observation optical sensor

The Moon is a potential new platform for Earth observation.The advantages of its large-scale observational scope,long temporal duration,and multi-layer detecting of the Earth will undoubtedly advance our understanding of the Earth system.To carry out the observations from a Moon-based optical sensor,the geolocation error caused by exterior orientation elements need to be investigated.This paper analyses the error effects of exterior orientation elements on geolocation for an optical sensor.To estimate the error,we present a geometric image model and utilise some parameters to measure the image offsets.Through a large number of numerical simulations,the results demonstrate that the image offsets are not obvious influenced by the distance and observation angle at mid-high latitude of the Moon and have linear correlation with the increasing errors of the exterior orientation elements.Further,the relationship between the spatial resolution and errors of exterior orientation elements are revealed.Finally,the error characteristics for Moon-based Earth observation are discussed.It is expected that the conclusion drawn in this paper could support the study of a Moon-based Earth observation optical sensor.

Transformation Method of Exterior Orientation Angular Elements Obtained via Position and Orientation System Under Gauss-Kruger Projection Coordinate System

Data obtained via airborne position and orientation system （POS） is in WGS 84 global geocentric reference frame, while the national coordinate reference system for topographic mapping in China is generally Gauss-Kruger projection coordinate system. Therefore, data obtained via a POS must be transformed to national coordinate system. Owing to the effects of earth curvature and me- ridian deviation, there are some errors in the process of angle transformation from roll, pitch, and heading （φ,θ,ψ） obtained directly via a POS to the attitude angles of images （φ,ω,κ） needed in photogrammetry. On the basis of effect theories of earth curvature and meridian deviation on exterior orientation angular elements of images, a method using a compensation matrix to correct the transformation errors from attitude angles obtained via the POS to exterior orientation angular elements of images is proposed in this paper. Moreover, the rigorous formula of the compensation matrix is deduced. Two sets of actual data obtained via a POS AV 510, which are different in scale and terrain, are selected and used to perform experiments. The empirical results not only indicate that the compensation matrix proposed in this paper is correct and practical but also show that transformation accuracy of exterior orientation angular elements obtained via the POS based on compensation matrix is relevant to the selection of vertical axis （a projection of central meridian） of Gauss-Kruger projection coordinate system; the proper vertical axis should be the Gauss-Kruger projection of the central meridian of projection zone in which the survey area locates. However, the transformation accuracy of exterior orientation angular elements is irrelevant to the choice of origin of coordinate system; it is appropriate that the origin of coordinate system locates at the center point of the survey area. Moreover, transformation accuracy of exterior orientation angular elements achieved based on the compensa- tion matrix deduced in this paper is higher than that obtained via the existing POS processing software.