Terrestrial Photogrammetry: Deploy Reclamation-wide, Develop Capabilities, Explore Applications for 3D Measurements
How can the Bureau of Reclamation (Reclamation) take advantage of photogrammetry technology and establish a miltidiscipline photogrammetry analysis team to speed up and improve the quality of data acquisition?
How can close range (terrestrial) photogrammetry technology be deployed throughout Reclamation so all offices have the opportunity to understand and use this new technology?
How can terrestrial photogrammetry methods for geologic mapping and characterizing rock structures advance the state of knowledge and methods for evaluating the potential for rock erosion and estimates of stream power at Reclamation structures?
How can terrestrial photogrammetry obtain volume measurements for in-place density calculations for various types of soils?
How can cheaper software process photographs and generate 3D models for measurement data?
Need and Benefit
Though this is a new proposal, it will build upon past research on terrestrial photogrammetry. This past year photogrammetry techniques were successfully deployed for the first time in the hydrualics laboratory and have been adopted for rapid and accurate modeling and measurement capabilities. Using a helium balloon for the first time was a huge success for use by the Flood Hydrology Group to develop models for streamflow effects. Terrestrial photogrammetry was successfully used in a tunnel for the first time at the Guernsey South spillway tunnel to obtain a scaled model and accurately obtain concrete erosion volumes. Camera equipment has been loaned to other disciplines and offices. This research has been tremendously successful and has led to the possibility of applying this technology to more diverse problems and programs. The technology is relevant to any situation in which where a measurement is required.
Reclamation is a recognized leader in using terrestrial photogrammetry to accurately obtain geologic and other data and create 3D models for use in analysis.
Because of the rapid acquisition of data with readily obtained photographs, terrestrial photogrammetry is revolutionizing how measurements are made in the field. Because of this, Reclamation is poised to use this technique for virtually every construction job to obtain as-excavated and as-built geology and topography; to monitor ongoing changes at dam sites using difference calculation modules in the software; and to expose and expand these measurement and modeling capabilities to other disciplines and other agencies.
Rock erosion research has been an important topic for many years. Significant research money has been spent in this direction with limited success. A few of the most important reasons for past failures in this area are:
- The high cost to construct large-scale models to simulate the rock and hydraulic conditions that are of interest and the relatively poor simulation that these models provide.
- The Rock Erosion Index/Stream Power method has some fundamental flaws in its formulation. The basic concept is sound, but requires some corrections to the formulation of the estimates for stream power and the rock erosion index.
+ Our hydraulics lab has found errors in the Stream Power estimates
+ Our geotechnical engineers have found weaknesses in the Rock Erosion Index estimate
The Rock Erosion Index is primarily a 2D system, and the primary factor affecting rock stability (Removability: a 3D geometric evaluation of the block shapes and the surface topology) is not included in the index. This is very different than the way rock stability issues are typically evaluated in virtually every rock stability problem Reclamation evaluates.
By obtaining data from sites that are undergoing the conditions for erosion we do not need to wait for remote flood events or build expensive, inadequate models that do not reflect reality. We would correct the stream power estimates and include rock block removability. This approach saves money and improves the reliability of the results. This program is anticipated to take several years to complete and it will not provide enough data to address a large variety of flow and rock conditions, but it would be a step in the right direction and should lead to a better understanding of this issue and a model for additional work that could lead to real progress in solving this very difficult issue. This work would be valuable to all entities that have issues with rock erosion, and it is not limited to Reclamation's dams. This approach provides a model for others to follow in an attempt to develop the data needed for addressing other flow and rock conditions.
Using photogrammetry to obtain volume for in-place density calculation would eliminate sand required to obtain volumes and allow for easily obtaining in-place density at remote sites.
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