Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model
Abstract As camera trapping has become a standard practice in wildlife ecology, developing techniques to extract additional information from images will increase the utility of generated data. Despite rapid advancements in camera trapping practices, methods for estimating animal size or distance fro...
Published in: | Methods in Ecology and Evolution |
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Online Access: | http://dx.doi.org/10.1111/2041-210x.13880 https://onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13880 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/2041-210X.13880 https://besjournals.onlinelibrary.wiley.com/doi/am-pdf/10.1111/2041-210X.13880 https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13880 |
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crwiley:10.1111/2041-210x.13880 2024-06-23T07:56:22+00:00 Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model Leorna, Scott Brinkman, Todd Fullman, Timothy Office of Polar Programs 2022 http://dx.doi.org/10.1111/2041-210x.13880 https://onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13880 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/2041-210X.13880 https://besjournals.onlinelibrary.wiley.com/doi/am-pdf/10.1111/2041-210X.13880 https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13880 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#am http://onlinelibrary.wiley.com/termsAndConditions#vor Methods in Ecology and Evolution volume 13, issue 8, page 1707-1718 ISSN 2041-210X 2041-210X journal-article 2022 crwiley https://doi.org/10.1111/2041-210x.13880 2024-06-04T06:38:08Z Abstract As camera trapping has become a standard practice in wildlife ecology, developing techniques to extract additional information from images will increase the utility of generated data. Despite rapid advancements in camera trapping practices, methods for estimating animal size or distance from the camera using captured images have not been standardized. Deriving animal sizes directly from images creates opportunities to collect wildlife metrics such as growth rates or changes in body condition. Distances to animals may be used to quantify important aspects of sampling design such as the effective area sampled or distribution of animals in the camera's field‐of‐view. We present a method of using pixel measurements in an image to estimate animal size or distance from the camera using a conceptual model in photogrammetry known as the ‘pinhole camera model’. We evaluated the performance of this approach both using stationary three‐dimensional animal targets and in a field setting using live captive reindeer Rangifer tarandus ranging in size and distance from the camera. We found total mean relative error of estimated animal sizes or distances from the cameras in our simulation was −3.0% and 3.3% and in our field setting was −8.6% and 10.5%, respectively. In our simulation, mean relative error of size or distance estimates were not statistically different between image settings within camera models, between camera models or between the measured dimension used in calculations. We provide recommendations for applying the pinhole camera model in a wildlife camera trapping context. Our approach of using the pinhole camera model to estimate animal size or distance from the camera produced robust estimates using a single image while remaining easy to implement and generalizable to different camera trap models and installations, thus enhancing its utility for a variety of camera trap applications and expanding opportunities to use camera trap images in novel ways. Article in Journal/Newspaper Rangifer tarandus Wiley Online Library Methods in Ecology and Evolution 13 8 1707 1718 |
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Wiley Online Library |
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English |
description |
Abstract As camera trapping has become a standard practice in wildlife ecology, developing techniques to extract additional information from images will increase the utility of generated data. Despite rapid advancements in camera trapping practices, methods for estimating animal size or distance from the camera using captured images have not been standardized. Deriving animal sizes directly from images creates opportunities to collect wildlife metrics such as growth rates or changes in body condition. Distances to animals may be used to quantify important aspects of sampling design such as the effective area sampled or distribution of animals in the camera's field‐of‐view. We present a method of using pixel measurements in an image to estimate animal size or distance from the camera using a conceptual model in photogrammetry known as the ‘pinhole camera model’. We evaluated the performance of this approach both using stationary three‐dimensional animal targets and in a field setting using live captive reindeer Rangifer tarandus ranging in size and distance from the camera. We found total mean relative error of estimated animal sizes or distances from the cameras in our simulation was −3.0% and 3.3% and in our field setting was −8.6% and 10.5%, respectively. In our simulation, mean relative error of size or distance estimates were not statistically different between image settings within camera models, between camera models or between the measured dimension used in calculations. We provide recommendations for applying the pinhole camera model in a wildlife camera trapping context. Our approach of using the pinhole camera model to estimate animal size or distance from the camera produced robust estimates using a single image while remaining easy to implement and generalizable to different camera trap models and installations, thus enhancing its utility for a variety of camera trap applications and expanding opportunities to use camera trap images in novel ways. |
author2 |
Office of Polar Programs |
format |
Article in Journal/Newspaper |
author |
Leorna, Scott Brinkman, Todd Fullman, Timothy |
spellingShingle |
Leorna, Scott Brinkman, Todd Fullman, Timothy Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model |
author_facet |
Leorna, Scott Brinkman, Todd Fullman, Timothy |
author_sort |
Leorna, Scott |
title |
Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model |
title_short |
Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model |
title_full |
Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model |
title_fullStr |
Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model |
title_full_unstemmed |
Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model |
title_sort |
estimating animal size or distance in camera trap images: photogrammetry using the pinhole camera model |
publisher |
Wiley |
publishDate |
2022 |
url |
http://dx.doi.org/10.1111/2041-210x.13880 https://onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13880 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/2041-210X.13880 https://besjournals.onlinelibrary.wiley.com/doi/am-pdf/10.1111/2041-210X.13880 https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/2041-210X.13880 |
genre |
Rangifer tarandus |
genre_facet |
Rangifer tarandus |
op_source |
Methods in Ecology and Evolution volume 13, issue 8, page 1707-1718 ISSN 2041-210X 2041-210X |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#am http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/2041-210x.13880 |
container_title |
Methods in Ecology and Evolution |
container_volume |
13 |
container_issue |
8 |
container_start_page |
1707 |
op_container_end_page |
1718 |
_version_ |
1802649424082501632 |