DARWIN - Dolphin Photo-identification Software Adaptations to Digital Camera Acquisition and Increased Matching Accuracy. Computation of Error between Outlines. Map the unknown to the database fin by using a three point affine transformation.
Adaptations to Digital Camera Acquisition and Increased Matching Accuracy
Computation of Error between Outlines
Algorithms for Outline Mapping
Results and Conclusions
Preliminary testing of the two approaches utilized a database of dorsal fin images for 200 individuals. A test set of fifty different dorsal fin images of known individuals were matched against the database. On average, both methods ranked the correct fin in the top 17% of the database. Using the “Quick & Dirty” method, the median rank was in the top 5%; using the “Optimal” method the median was in the top 8%. However, we have observed that the transformations produced by the “Optimal” method produce a more accurate alignment – thus further refinement of the error metric is needed.
These results suggest that the registration methods presented herein show significant promise in perspective correction of dolphin dorsal fin images. The iterative nature of the alignment algorithm makes it less sensitive to the original designation of the outline or subsequent identification of feature points. In any case, the process has the ability to improve the registration of outlines considerably. The improved registration suitably corrects for perspective distortion and makes fin outline comparisons easier and aids in the subsequent retrieval of appropriate images.
Dorsal Fin Identification
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3. Active contours  are employed
to accurately position the points comprising the outline onto the actual edge of the fin.
4. Feature points along the outline are identified and used to perform a registration of the two fins.
5. Error between the registered outlines is computed and used to rank order the fins in terms of similarity.
This research was supported by the National Science Foundation under grant numbers DBI-0445126 and IIS-9980031. Additional funding was provided by National Marine Fisheries Services and Eckerd College. Dorsal fin images courtesy of Eckerd College Dolphin Project.
Figure 2:The tracing window allows the user to perform a sketch based query of the database of dorsal fins. This window is also used to add new dorsal fin images and associated sighting data to the database.
K. R. Debure, J. H. Stewman, S. A. Hale, Eckerd College, St. Petersburg, FL
Automatic Outline Generation
DARWIN is a computer program that automates the photo-identification of dolphins from photographs of dorsal fins. This program allows researchers to query a database of previously identified dorsal fin images with a digital image of an unidentified dolphin's fin. The system responds with a rank ordered list of database fin images most closely resembling the query image. In this way DARWIN assists researchers to prioritize their search of database images, and potentially reduces the time required for identification.
As digital cameras rapidly replace traditional film cameras for the acquisition of data in the field, adaptation of the software in response to the changing needs of the user community is critical. Compatibility with appropriate image formats, efficient handling of higher resolution image data, and automation and streamlining of data entry can facilitate the processing of increasing quantities of field data. The automated generation of the outline is one example of an effort to reduce data entry requirements.
In addition, to further increase the matching accuracy and the realistic utility of the DARWIN software, the most successful aspects of a quantitative dorsal fin matching approach have been incorporated within a broad hierarchical approach using qualitative distinctions between fins. This recently enhanced software (1) facilitates subset searches of the database based on damage
category (missing tip, etc), (2) selects more intuitive transformations for alignment, and (3) more closely emulates the manual photo-identification process.
DARWIN is a computer program which aids marine mammalogists in the identification of dolphins and in the management of a database of observational information. DARWIN graphically presents the digitized dorsal fin images and associated textual sighting information.
Figure 1:Following a query of the dorsal fin database, DARWIN presents a list of database images which most closely resemble the unknown fin image.
Figure 3:Upper and center left: Automatically generated dorsal fin outlines. Upper and center right: Common feature points (the start of the leading edge, the end of the leading edge, the tip, the most prominent notch and the end of the trailing edge) are identified along the outline. Bottom left: Original outlines of the database and unknown fin are superimposed before alignment. Bottom center: Outlines are partially registered following an affine transform based on a triplet of feature points. Bottom right: Fully registered outlines after an iterative alignment approach.