In: Wagner W., Szekely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
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higher resolution using bi-cubic interpolation prior to the actual 
image correlation performs better than both interpolation of the 
correlation surface using the same algorithm and peak 
localisation using curve fitting. Correlation peak localisation 
using Gaussian and polynomial algorithms are inferior in such 
applications. 
Therefore, we conclude that more precise and accurate 
displacement measurements are obtained by interpolating the 
available images to a higher resolution using bi-cubic 
interpolation prior to matching. In such approaches, one can 
gain over 40% reduction in mean error by interpolating the 
images to up to 1/16 th of a pixel. Interpolating to a more detailed 
sub-pixel resolution than 1/16 th of a pixel does not add much. 
Or in other words, when matching low-resolution images using 
normalized cross-correlation with intensity-interpolation based 
sub-pixel precision, 40% or better accuracy increment can be 
achieved compared to pixel-precision matching of images in 
reference to the same original resolution as the interpolated one. 
When real low-resolution images are used together with varying 
sizes of the matching entities, as opposed to the approach used 
in this study, even better precision and accuracy might be 
obtained as the noise due to resampling will not be present, and 
template and search window sizes will be adjusted with the 
pixel size. 
It should also be noted that although the relative performances 
of the algorithms is expected to be valid at least for other spatial 
domain matching approaches and for other applications, the 
magnitudes given here are strictly only valid for the similarity 
measure and test sites used in this paper. Futher research is 
needed for their validity outside the conditions described in this 
study. 
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ACKNOWLEDGEMENTS 
The research was conducted at the Geosciences department of 
the University of Oslo and financially supported by the 
Norwegian Research Council (CORRIA project). The authors 
are very grateful to both institutions.