The purpose of this report is to examine and investigate the use of the High-Resolutions Digital Stereo Photography in measuring erosion as well as the use of digital photography to analyse surface texture.
Both these procedures have the ability to rapidly analyse and produce data that may be applicable to all types of geotechnical relevance. The process of photogrammetry and the surface texture computation involve the use of software analysis. These computer aided software enable the user to produce results relatively quickly as opposed to traditional laboratory tests and field sampling.
The applicability of the photogrammetry software to large surface areas is a promising direction in terms of assessing and determining the performance of particular processes. Processes such as rehabilitated landforms and earthworks, with particular reference to the cost effectiveness, re-vegetative purpose as well as regulation compliances associated with particular areas.
The initial objectives were to acquire information and data on the specific sites. The sites that were selected were previously investigated in past project theses. These theses should respectively be used as a comparison in order to measure the amount of erosion that has occurred in the previous year.
Three sites were located at the ClayPave Sales office location near Dinmore. The first site was used previously; however this year the site has been covered with a large amount of course material making it unusable for this project. Site 2 and 3 were located on a wide waste slope which consisted of gullies and ridges. The sites displayed various forms of erosion and were analysed by using both the photogrammetry process as well as the particle distribution process.
The site images were obtained by photographing the selected areas from a baseline with a corresponding focal point. This raw image was then analysed using Siro 3D and a set of coordinates were obtained at the end. This data was then exported into the Surfer 7.0 program and converted into a grid file which was then effectively used to model contour maps and 3D wireframe images. This particular grid file was used to compute the total volume of the selected area within a site.
By calculating this volume, a comparison could then be made to the previous year’s results. However, due to inconsistencies and loss of data for the previous year, a complete photogrammetric analysis was done for the previous year as well as 2008. The same area was selected to perform this task and the results achieved,
produced a volume. This volume was then subtracted from last year’s to generate a volume loss for 2008. The erosion loss rate was slightly higher compared to last year’s, but this can be attributed to the higher than average rainfall that occurred in Amberley near the site location.
A particle size distribution was completed for both sites. Two methods were chosen, including a laboratory test and a computed test. Split Desktop was the software used to produce the particle size distribution data. Photos were taken of both sites and an analysis on the surface layer, and sub surface layer was completed. The lab test was done by taking a sample of soil from site 3 and running it through a series of sieves, thus getting a distribution of size for that specific location. The results demonstrated that the computed particle size distribution was not as accurate as the lab tests in determining the finer particles.
An accuracy test was also performed for the Siro 3D software. Site 2 was chosen as the test parameter. Initially when the photographs were taken, two separate photos of site two were taken from the same baseline. The same process was used in determining the volume of Site 2. The test illustrated an error of 0.81% thus proving that the Sirovision software was quite accurate.
The principal recommendations arising from the results include that there must be acknowledgement of the capabilities and limitations of photogrammetry. Also the use of photography based particle size distribution is recommended only for use as a preliminary estimate of soils. Overall both processes provide some form of relevant information in terms of erosion loss and are definitely site specific and user manipulated.