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TitleAn evaluation of sun angle computation algorithms
AuthorTeillet, P M; Lasserre, M; Vigneault, C G
Source10th Canadian Symposium on Remote Sensing/10e Symposium canadien sur la télédétection; vol. 1, 1986 p. 91-100
Alt SeriesEarth Sciences Sector, Contribution Series 20040587
Alt SeriesRESORS 1057229
Meeting10th Canadian Symposium on Remote Sensing - 10e Symposium canadien sur la télédétection; Edmonton, Alberta; CA; May 5-8, 1986
AbstractSun angle computations were studied in the context of remote sensing. For general-purpose use involving readily available, low-precision formulae, errors due to the choice of algorithm are very much less than errors due to location uncertainty and seasonal variations. High-precision determinations of solar illumination angles become important if accurate shadow areas are to be derived from digital terrain information.
An error analysis was carried out to assess and rank the principal sources of uncertainty in the solar position as they might occur in the framework of LANDSAT image data. The concept of uncertainty ellipses is used to illustrate errors in sun angle due to finite solar diameter, finite scene acquisition time, within-scene location variations, and the use of values from an inappropriate epoch. Using a digital elevation model for the Anderson River area in British Columbia, and analysis was carried out to show the strong effect of errors in sun angle on the determination of shadow regions.
Issues dealing with computer implementation of sun angle algorithms, solar information provided with image data tapes, and the influence of atmospheric refraction on apparent solar position are also examined.

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