problems, is proposed and described in detail. The method is successfully applied to estimate crystalline homogeneity of a square indium-arsenide plate epitaxially-grown on gallium-arsenide substrate. To this end, the specimen is tested in nine areas around points forming a square grid. It is demonstrated that whole specimen may be regarded as a single large crystalline grain consisting of crystallites separated by small-angle boundaries. The crystallites occur as rode-like cuboids elongated in the direction perpendicular to the plate surface, with different areas of the sample and with base sizes not much differing. The mean-absolute second-order strain is very small and almost constant in the whole sample. The first-order strain also appears and, effectively, the structure of the crystalline layer is tetragonal with unit-cell parameters being smaller parallelly and larger perpendicularly to the layer surface and varying slightly in the layer. The results are presented in tables and figures and commented.