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Measuring distances using digital cameras


Kendal, D, Measuring distances using digital cameras, Australian Senior Mathematics Journal, 21, (2) pp. 24-28. ISSN 0819-4564 (2007) [Refereed Article]

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This paper presents a generic method of calculating accurate horizontal and vertical object distances from digital images taken with any digital camera and lens combination, where the object plane is parallel to the image plane or tilted in the vertical plane. This method was developed for a project investigating the size, density and spatial distribution of shrubs growing as hedges.

The geometry of objects projected on to parallel and oblique image planes was used to develop an equation for calculating horizontal and vertical distances from image pixel counts. Images of a grid were taken with a variety of digital cameras at different focal lengths, image-object distances and vertical tilt angles. The equations were also tested by taking a set of photos of shrubs in hedge field experiment.

The results show a very strong correlation between calculated distances and physical measurements across a range of cameras, focal lengths, distances and vertical tilt angles. A small constant error was found in two of the three cameras tested suggesting that effective image size may vary from published sensor dimensions in some cameras. Cameras should be calibrated to check for any constant error before using the equations described in this paper.

Item Details

Item Type:Refereed Article
Keywords:image analysis, distance measurement
Research Division:Built Environment and Design
Research Group:Urban and regional planning
Research Field:Land use and environmental planning
Objective Division:Environmental Management
Objective Group:Terrestrial systems and management
Objective Field:Terrestrial biodiversity
UTAS Author:Kendal, D (Dr Dave Kendal)
ID Code:124660
Year Published:2007
Deposited By:Geography and Spatial Science
Deposited On:2018-03-02
Last Modified:2018-04-16

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