Fig 1.
Location of study area in the eastern Canadian Arctic (inset) with a panchromatic WorldView-3 satellite image (catid: 1040010061AFA400) used in this study to develop an algorithm to semi-automate identification of beluga whales.
The top right inset shows an example of a beluga whale and calf at a scale of 1:500. (Reprinted under a CC BY license, with permission from Maxar Technologies, original copyright 2020).
Fig 2.
Examples of (a) the original panchromatic WorldView-3 satellite image (no stretch) and (b) the same tile of the satellite image after a high-pass filter was applied. Both images are at a scale of 1:250. (Reprinted under a CC BY license, with permission from Maxar Technologies, original copyright 2020).
Fig 3.
Example of image segmentation.
The image on the left represents the original image showing the location of the whales, while the image on the right illustrates the segments produced by the OBIA method (using an EDGE segment algorithm with a scale level of 90) and a FAST LAMBDA merge algorithm with a merge level of 40). (Reprinted under a CC BY license, with permission from Maxar Technologies, original copyright 2020).
Table 1.
The eleven ‘best’ candidate OBIA algorithms used in this study to identify beluga whale locations.
The segment algorithm was EDGE and the merge algorithm was FAST LAMBDA for all of the eleven algorithms listed.
Fig 4.
Examples of OBIA of beluga whales for two tiles from the original WorldView-3 satellite image.
Both images are at a scale of 1:250. Arrows indicate multiple segments of the same whale. (Reprinted under a CC BY license, with permission from Maxar Technologies, original copyright 2020).
Table 2.
Accuracy assessment matrix for the eleven candidate algorithms for the training tile (20AUG05_R3C2) and the test tile (20AUG05_R2C3).
Observer #1 visually identified a total of 32 whales in 20AUG05_R3C2 and 190 in 20AUG05_R2C3, while observer #2 detected 34 and 193 whales respectively. The total number of identified whales (total count) are those identified by both observers. The time required to identify the whales in each image is included in the last column (average time for the candidate algorithms).
Fig 5.
Examples of issues with the detection of beluga whales in the WorldView-3 satellite imagery: (a) grouped whales, (b) whales below the surface, and (c) multiple segments for each whale. Arrow indicates submerged whale in the image. (Reprinted under a CC BY license, with permission from Maxar Technologies, original copyright 2020).