The HemiView canopy image analysis system provides the hardware and software needed to acquire and analyse hemispherical images of forest canopies.

Specification

 

Image file types	BMP, JPG, TIF, Photo CD.
Lens distortion	Can be specified as a polynomial relating zenith angle and radial distance.
Direct light model	Simple atmospheric transmission, with user defined settings.
Diffuse light model	Uniform or Standard overcast sky.
Data output	Excel compatible spreadsheet built-in.

Outputs

 

Sky Geometry	Centroid, solid angle and pixel count for each sky sector.
Gap Fraction	Proportion of visible sky by sector.
Leaf Area Index	By sky sector or overall value.
Solar Radiation	Direct and diffuse, above and below the canopy, in energy or molar units.
Site Factors	Direct, indirect (diffuse), global.
Time series and Sunflecks	Visibility of the solar disc (penumbral effects) and solar irradiance on chosen days, sampled at user-defined intervals or summarised as a sunfleck sequence.
Optional cosine correction	For any orientation of intercepting surface.
Overall values	Most outputs can be tabulated by sky sector, or aggregated into a single overall whole sky or annual value.

Features

 

Interactive graphical alignment tool	Precise registration of images with the hemispherical co-ordinate system. Compensates for magnetic declination.
Responsive image classification	Threshold intensity discriminates visible and obstructed pixels. The classified image view is updated in real-time.
Multiple and split views on any image	Classified and colour / grey scale views, or separate sections of a large image can be viewed side by side.
Negative images	Photographic negatives can be viewed and analysed as positives.
User-defined number of diffuse sky regions	Enables use of custom ranges of zenith and azimuth angle.
Leaf Area of a Single Tree	Excel spreadsheet provided with instructions for calculating single tree LAI using HemiView outputs.
Analysis of partial images	Unwanted parts of images can be ignored by the analysis.
Configurable for site, lens, solar model	User-defined site, lens and solar model characteristics can be applied to any image by selecting from a list.
Pre-defined lens characteristics	Lens equations are provided for current and previous lens types supplied by Delta-T Devices
Results output to Excel compatible workbook	Additional calculations can be performed using standard spreadsheet formulae. Alternatively, workbooks can be saved for further analysis using Excel. Results can be appended to existing workbooks.
User-defined output configurations	The user can define multiple custom output configurations which can be applied to different images.

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