AragoJ: A free, open‐source software to aid single camera photogrammetry studies

Aleixo, Francisco; O’Callaghan, Seán A.; Soares, Luís Ducla; Nunes, Paulo; Prieto, Rui

doi:10.1111/2041-210x.13376

Cited by 8 publications

(10 citation statements)

References 47 publications

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“…Low distortion lenses help alleviate these problems, but often at a financial cost. In some cases, specific lens-camera combinations can be paired to further reduce distortion through physical and electronic corrections, and through software workflows that correct camera distortions [162]. Distortion can be alleviated using software post-flight, but will not produce results as good as with a low-distortion lens.…”

Section: Individual Samplingmentioning

confidence: 99%

Operational Protocols for the Use of Drones in Marine Animal Research

Raoult

Colefax²,

Allan

et al. 2020

Drones

100

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The use of drones to study marine animals shows promise for the examination of numerous aspects of their ecology, behaviour, health and movement patterns. However, the responses of some marine phyla to the presence of drones varies broadly, as do the general operational protocols used to study them. Inconsistent methodological approaches could lead to difficulties comparing studies and can call into question the repeatability of research. This review draws on current literature and researchers with a wealth of practical experience to outline the idiosyncrasies of studying various marine taxa with drones. We also outline current best practice for drone operation in marine environments based on the literature and our practical experience in the field. The protocols outlined herein will be of use to researchers interested in incorporating drones as a tool into their research on marine animals and will help form consistent approaches for drone-based studies in the future.

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Section: Individual Samplingmentioning

confidence: 99%

Operational Protocols for the Use of Drones in Marine Animal Research

Raoult

Colefax²,

Allan

et al. 2020

Drones

100

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“…focal length, sensor size) of the camera trap used to collect images is necessary to estimate animal sizes or distances accurately and precisely. Other methods and tools have been used when the physical specifications of cameras are known (Aleixo et al, 2020; Berger, 2012; Meise et al, 2014); however, many camera trap manufacturers do not report this information. For example, the physical sensor size and focal length of the Reconyx Hyperfire 2 HF2X cameras that we used were not reported by the manufacturer nor available in image metadata.…”

Section: Discussionmentioning

confidence: 99%

“…Optical distortions are unique to each specific set of technical camera specifications and lens characteristics, but in general, error size will increase as the position of the object moves away from the centre of the image and as the dimension being measured covers a larger portion of the image (e.g. if the animal is very close to the camera such that the dimension being measured covers most of the image; Aleixo et al, 2020; Neale et al, 2011). Typically, the wider the camera field‐of‐view, the greater effect these factors have towards the edges of the image (Figure S1; Kannala et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…Based on the field‐of‐view of most camera traps (<50 degrees; Trolliet et al, 2014), optical distortions are unlikely to be a major issue for most wildlife camera trap applications; however, there are multiple ways to account for this if extremely high precision and accuracy are necessary (e.g. barrel distortion correction; Aleixo et al, 2020; Kannala et al, 2008). While specific project conditions and objectives will likely determine the desired level of accuracy and precision in estimated animal sizes and distances, being aware of these limitations and considerations will help ensure the best possible results are achieved when applying the pinhole camera method.…”

Section: Discussionmentioning

confidence: 99%

“…Our main goal was to identify and describe a simple and generalizable method of deriving either animal size or distance from the camera directly from camera trap images to support growing analytical approaches and camera trap applications. Broadly, extracting information about the physical three-dimensional scene captured in two dimensions of an image is often referred to as the field of photogrammetry (Aleixo et al, 2020;Kannala et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

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Estimating animal size or distance in camera trap images: Photogrammetry using the pinhole camera model

Leorna

Brinkman

Fullman³

2022

Methods Ecol Evol

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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.

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