User Manual - pancroma

high pixel brightness in one image corresponds perfectly to low pixel brightnessin the other. A coefficient of zero means that there is no correspondence at allbetween the two images.Iterative InterpolationPANCROMA TM offers an implementation of the Franklin Approximationinterpolation algorithm as a stand-alone utility. The Franklin Approximation,implemented using the Iterative solver (with an initial estimate computed usingthe Laplacian convolution mask) has many advantages over other interpolationmethods. The algorithm may be used for general interpolation tasks, for examplethe interpolation of elevation contour lines into digital elevation models (DEMs).To use the utility, open a JPEG or BMP input file by selecting ‘File’ | ‘Open’.Then select ‘Pre Process’ | ‘Iterative Interpolation’ | ‘JPEG/BMP’. The imageprocessing data input box will automatically open. Default values for Laplacian,Iterative and Thin Plate interpolation counts will be entered. Accept these orinput your own values. The interpolation will be computed when you click‘Process Image’.Input file size is limited to 3000 X 3000 rows and columns or equivalent due tothe large amount of RAM required for the Iterative solver data structures. Atpresent, the utility is only implemented for JPEG and BMP input files. Contact usif you wish to input alternative formats.Landsat 7 Image RegistrationPrevious sections have discussed the PANCROMA TM image registration utilitiesdesigned specifically for subsetting and co-registering sets of Landsat band filesfor gap-filling and cloud masking. These utilities, although powerful, have certainlimitations. They always are combined with subsetting and row and columnrationalizing steps. They automatically select ground reference points usingcommon UTM latitude and longitude coordinates. When rescaling, they alwaysrescale the larger scale image down to the size of the smaller scale image.Sometimes you may need a general image registration utility that merely alignstwo images without cropping or subsetting either of them. You may wish to useground control points rather than latitude and longitude, and you may wish tointerpolate the smaller image to that of the larger scale. PANCROMA TMpreprocessing image registration utility can do this.Image registration is the process of aligning two images of the same area of theearth such that they correspond to each other on an exact pixel-by-pixel basis.This can be thought of as holding two image transparencies up to the light – ifproperly registered the land and water features will overlap exactly. It is rarelypossible to produce a perfectly exact match. However, it is generally possible toproduce very close matches for certain classes of images. One example is174