I have refrained from commenting in many instances in past posts: But I will now bring a few to light.
How can a person demonstrate competency in a subject discussion when acting as if they are "joining in" on a technical discussion "on par", when the statement of using LIDAR infers incompetency in the subject matter at hand? (Post 3659) jpal: "A high res 3D profile of the dam should be generated from terrestrial Lidar"
The best digital processing of LIDAR data has a resolution of 3.9 inches (even without the additional grass vegetation modulation of the data since it is "reflected light based readings"). To detect any "differential settlement" profiles in a one, two, or multiple year span (two separate readings to compare against), you must have millimeter accuracy. Only satellite Interferometric Synthetic Aperture Radar (InSAR) has the ability to measure to millimeters. I would say that a millimeter range near 0.03937 inches is much more definitive than 3.9 inches (99x).
Learn what you are talking about before joining in as if you know.
PavewayIV revealed this insight "clue" in that he was unable to find LIDAR mappings of a dam (post 3573). That's because you cannot get the accuracy to measure the precision settlement that is necessary from the course LIDAR method. (see Svartevatn dam measured using Satellite InSAR with rates defined in millimeters).
Another subject:
You wanted to discuss a technical array of microprocessor based sensors to emplace in the new spillway. Fine. When presented with very detailed and technical challenges to high-reliability systems regarding modern day microprocessors, supporting supply electronics, and the C++ compilers & execution code tree verifiability... No response. I didn't even bring up the survivability issues with arresting ESD life & degradation protection from lightning discharges that undoubtably occur from thunderstorms that could strike near the spillway.
If a person wants to enter into a discussion at a level that they come across in detail to discuss - Learn what you are talking about - or if you need help, engage to ask questions to come up to speed.
This is one of of the best threads ever on FR. Thanks for sticking around and providing your insight.
Hi EarthResearcher333.
Regarding issues you raised in post 3717:
LIDAR
The LIDAR used for the “Google car” and many other autonomous vehicles has a stated accuracy of 2cm http://velodynelidar.com/hdl-64e.html , although it does sample millions of times a second, yielding a point cloud resolution better than that for flat surfaces like roadways. Measurement of the large cobbles on the upstream slope of the dam would be noisy, but this could be partially mitigated by oversampling. As you say, the grassy downstream slope would be more of a issue, especially with the Green Spot grass at varying heights.
However, I think such a point cloud resolution should be sufficient to investigate if there are substantial settlement discontinuities across the dam. This would not have the resolution of InSAR, but would be faster/cheaper/more available for a preliminary investigation. Either measurement technique would have to tie into the same survey monuments used for the 1975 DWR Settlement Report cited in post 3624 (or others as available) to determine the past time rate of settlement.
Microprocessors
I suggested the use of an array of microprocessor based moisture sensors to determine if the Green Spot moisture is correlated with reservoir elevation. These are COTS items commonly used in California during the drought - simple and cheap enough that they can be quickly installed. To me, the most critical question is “Dose reservoir water seep through the face of the dam”, and these embedded micro controllers would help determine that question one way or another.
I also suggested that some type of access to instrumentation be embedded in the new spillway as it is being constructed so as to better diagnose problems before they manifest. In lieu of dragging chains over the spillway in the hope that a trained ear will pick up subtle changes over the years, perhaps it might be better to have embedded microphones detect any acoustic changes as a function of spillway flow? My post was more concerned with the types of detection that might be useful, rather than how to write C code to collect the data.
Lighting can fry any outdoor electronics, but that’s not real common in that area of California. However, critical instrumentation should be accessible and replaceable if it fails for any reason.