The Digital Gravelometer is based on proven technology that has been published in the highly respected academic journals Water Resources Research and Mathematical Geology. Links to these academic papers may be found at Loughborough University’s Physical Geography Resources Gateway.
For full details of the technology used you should follow the link above or view the documentation, but in essence the software applies the following procedure to each image:
- Convert to grayscale
- Correct for radial lens distortion
- Correct for the camera axis not being perpendicular to the surface
- Identify individual grains
- Select those grains within a defined area
- Measure the selected grains
- Correct the results to make comparable with square-hole sieves (if required)
- Calculate the desired grain-size distribution parameters and statistics and output the results
The identification of the individual grains (step 4) is itself composed of a series of image-processing stages that are designed to be highly robust, producing excellent results on images of sediments with a diverse range of physical properties without the need for reparameterization. Nevertheless, should the user desire, the parameters used within the grain-identification procedure may be modified.
Whilst it is not essential to understand the details of the technology in order to obtain reliable grain-size information, users will benefit from taking the time to do so, particularly if they wish to adjust the grain-identification parameters.
Full details of the image-processing methods are included within the documentation.