Tham khảo tài liệu 'mobile robots -towards new applications 2008 part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Learning Features For Identifying Dolphins 431 This idea is reinforced by Cesar and Costa 1997 that explain how energy curvature diagrams of multi-scales can be easily obtained from curve graphics Cesar 1996 and used as a robust feature for morphometric characterization of neural cells. That is the curvature energy is an interesting global feature for shape characterization expressing the quantity of energy necessary for transforming a specific shape inside its most down energy state a circle . The curvegram which can be precisely obtained by using image processing techniques more specifically through the Fourier transform and its inverse provides a multi-scale representation of digital contour curvatures. The same work also discusses that by the normalization of the curvature energy with respect to the standard circle of unitary perimeter this characteristic gets efficient for expressing complex shapes in such a way it is invariant to rotation translation and scale. Besides it is robust to noise and other artefacts that imply in image acquisition. Just recently Gope et al 2005 have introduced an affine curve matching method that uses the area of mismatch between a query and a database curve. This area is obtained by optimally aligning the curves based on the minimum affine distance involving their distinguishing points. From all observed works we could see that the major difficulties encountered by researchers is in the comparison between several individuals photographed in different situations including time clime and even different photographers. These and other issues insert certain subjectivity in the analysis done from picture to picture for a correct classification of individuals. Photo analysis is based mainly in the patterns presented by the dorsal fin of the animals. That is identification has been carried out mostly by identifying remarkable features on the dorsal fin and visually comparing it with other pictures following a union of affine features. .