Remote estimation of grey seal length, width and body mass from aerial photography

Twiss, S.D.; Pomeroy, P.P.; Thomas, C.J.; Mills, J.P.

Remote estimation of grey seal length, width and body mass from aerial photography

Twiss, S.D.; Pomeroy, P.P.; Thomas, C.J.; Mills, J.P.

Authors

Dr Sean Twiss s.d.twiss@durham.ac.uk
Associate Professor

P.P. Pomeroy

C.J. Thomas

J.P. Mills

Abstract

High-resolution images of two UK grey seal breeding colonies were derived from multi-temporal aerial photography and geo-referenced in a GIS using ground control points obtained in the field with sub-meter DGPS. Lengths and widths of seals were digitized from these images. Elevations at seal locations were determined using sub-meter DEMs, allowing measurements to be adjusted for proximity to the camera. Mass estimates of seals were computed from these measures using models developed from direct field measurements. Comparisons of estimates derived from the images and actual masses of seals measured in the field indicate that this method provides a consistent index of relative body size. Seasonal patterns of changes in remotely determined size and mass estimates and inter-colony comparisons mirrored patterns observed from direct field measurements. Our work permits the remote estimation of seal body size for any sample of seals without the intrusive complications and sample limitations of direct field measurements.

Citation

Twiss, S., Pomeroy, P., Thomas, C., & Mills, J. (2000). Remote estimation of grey seal length, width and body mass from aerial photography. Photogrammetric engineering and remote sensing, 66(7), 859-866

Journal Article Type	Article
Publication Date	Jul 1, 2000
Deposit Date	Mar 17, 2014
Publicly Available Date	Sep 1, 2015
Journal	Photogrammetric engineering and remote sensing.
Print ISSN	0099-1112
Publisher	American Society for Photogrammetry & Remote Sensing
Peer Reviewed	Peer Reviewed
Volume	66
Issue	7
Pages	859-866
Keywords	Halichoerus-Grypus, North-Rona, Site fidelity, Scotland, Success, Size, Dipersion.
Publisher URL	http://www.asprs.org/PE-RS-Journals-2000/PE-RS-July-2000.html