# Presentation: 230211

## Representation and Retrieval Issues in DARWIN:

**Representation and Retrieval Issues ****in DARWIN:**

- Kelly R. Debure, Eckerd College, St.Petersburg, FL

- Digital Analysis and Recognition of Whale Images on a Network

## Background

-    Identification of individual animals is necessary for the study of behavioral and ecological patterns
- Artificial markings
- Manual photo-identification based on natural markings

## Photo-Identification

- Dolphin dorsal fins with distinctive natural markings

## The DARWIN Project

- Goals:

## The DARWIN Project

- Goals:
- provide access to a database of digital images of dolphin dorsal fins

## The DARWIN Project

- Goals:
- provide access to a database of digital images of dolphin dorsal fins
- storage and retrieval of observational data which accompanies each fin

## The DARWIN Project

- Goals:
- provide access to a database of digital images of dolphin dorsal fins
- storage and retrieval of observational data which accompanies each fin
- enable access to images and data across a network

## The DARWIN Project

- Goals:
- provide access to a database of digital images of dolphin dorsal fins
- storage and retrieval of observational data which accompanies each fin
- enable access to images and data across a network
- reduce the tedium of manual cataloging and access of individual dorsal fins

## The DARWIN Project

- History:
- Initially implemented in 1996 by undergraduate student Mark Allen under the direction of John Stewman
- Originated as and remains a collaborative effort with the Eckerd College Dolphin Research Group headed by John E Reynolds, III
- Originally implemented on a PC under Windows, ported to Unix in 1998 by undergraduate student Dan Wilkin
- Evaluated by Kim Urian, curator of National Marine Fisheries Service Mid-Atlantic Bottlenose Dolphin Photo-ID Catalog

## Query Generation

- Currently, the user searches for an unknown fin in a database of previously identified fins using a semi-automated sketch based query mechanism.

## Query Generation

-   user traces a broad outline of the leading
-      and trailing edges of the dorsal fin with
-      the cursor

## Query Generation

-   user traces a broad outline of the leading
-      and trailing edges of the dorsal fin with
-      the cursor
-   center of trace initializes the positions of a
-      series of evenly spaced points positioned
-      along the fin edge

## Query Generation

-   user traces a broad outline of the leading
-      and trailing edges of the dorsal fin with
-      the cursor
-   center of trace initializes the positions of a
-      series of evenly spaced points positioned
-      along the fin edge
-   active contours move the points from the
-      initial locations to the actual edge of the fin

## Query Generation

-   user traces a broad outline of the leading
-      and trailing edges of the dorsal fin with
-      the cursor
-   center of trace initializes the positions of a
-      series of evenly spaced points positioned
-      along the fin edge
-   active contours move the points from the
-      initial locations to the actual edge of the fin
-   an outline of the dorsal fin is produced

## Query Generation

- Currently, the user searches for an unknown fin in a database of previously identified fins using a semi-automated sketch based query mechanism.
- The outline is transformed into a representation suitable for efficient comparison with outlines in the database

## Query Generation

-    query method is somewhat labor intensive
-    automate generation of initial outline
-    increase sensitivity to deep concave structures

## Outline Representation

- From a computational standpoint, the ability to reduce the representation of a dorsal fin outline from a sequence of Cartesian coordinates to a representation of distances along fixed distance increments greatly simplifies the comparison of outlines.
-   Reduces the complexity of the computation of the error
-      measure
-   Solves some of the problems of comparison, namely
-      translational differences between the fin outlines

## Centroid Signature Representation

- From an outline comprised of Cartesian coordinates a centroid signature is computed as follows:
-   Calculate the centroid (cx,cy) as the average x and y
-       values of the outline coordinates.
-   From the centroid, construct a ray at 0 degrees that
-       intersects the outline of the fin at (x1,y1).
-   Compute the distance from (cx,cy) to (x1,y1) and store
-      the distance as the signature value for that angle.
-   Increment the angle by one degree, and repeat the
-      process for each of 360 degrees.

## Centroid Signature Representation

## Centroid Signature Comparison

- Rotation angle clockwise (degrees)

- Normalized distance of fin outline from centroid (pixels)

- Rotation angle clockwise (degrees)

- Signature error

##  Original Representation Scheme

- Centroid signature representation scheme is effective in reducing the dimensionality of the matching problem.  However...
-   Match measurement based upon overall fin
-      shape instead of fin damage
-   Correction of rotational differences was iterative in
-      nature and computationally intensive.
-   Normalization of the average distance from the
-      centroid to the outline to correct scale differences.

## Computation of Relative Chain Code

- From an outline comprised of Cartesian coordinates the relative chain code is computed as follows:
-   Compute the length L of the line segments which result
-       when the outline is partitioned into 180 segments of
-       equal length.
-   Compute the point (x1,y1) at which an arc of length L,
-       originating at the bottom most point, (xo, yo), of the
-       leading edge, intersects the outline.
-   Compute the bearing from (x0, y0) to (x1, y1), and store
-       the difference between the current and previous bearing.
-   Repeat the process for each segment

## Relative Chain Code Representation

## Relative Chain Code Comparison

- Signature error

- Line segment index

## Slide 25

## Outline Representation Improvements

-    Distance between key points effectively used in the
-       computation of a scaling factor.
-   Rotational differences do not significantly impact the
-      resulting chain values.
-   Efficiency/speed greatly improved

## Representation Shortfalls

- Ignores surface scarring such as rake marks

## Representation Shortfalls

- Lack of significant notch causes scaling error

## Representation Shortfalls

- Fails for severely mutilated fins

## DARWIN TEAM

- Mark Allen
- Dan Wilkin
- Zach Roberts
- John Stewman
- Kelly Debure
- John E. Reynolds, III

## Representation and Retrieval Issues in DARWIN:

**Representation and Retrieval Issues ****in DARWIN:**

- Kelly R. Debure, Eckerd College, St.Petersburg, FL

- Digital Analysis and Recognition of Whale Images on a Network