MrMaker

Hi, Sandor, Stu. Any updates on this? Wasn't the next experiment supposed to happen last December? Regards

How did you estimate this non-uniform area to be in the 50cm range? If this is only an idea to explain the "bottom of the boat seems to disappear" part, you need additional data to analyse that. The common conception would be that the bottom of the boat disappears due to the water curvature, and not refraction. I don't think that what Sandor wants to measure is the bottom of the boat, though, as that would lead to a rather different experiment, tools and planning. I would leave this "bottom of the boat" analysis to a different moment. Additionally to the NUDTZ existance, and existing only below 50cm hypothesis, there is clearly something other than your NUDTZ taking place at 1.35m+. The trembling laser, the laser going down and reflecting back up, etc, needs to be explained and measured. From everything that I read I though this NUDTZ idea was to explain all the erratic laser behavior during the whole experiment. Anyway, add to my list of suggestion to forget about NUDTZ and think only about getting all the data the correct way. As someone mentioned here, try to formulate hypothesis after you get the data correct, not before. That's great. Don't forget any suggestions, I'd say. If you are willing to share the next experiment setup, before or after you discuss with the university specialists, I think a lot of people will be happy to keep debating it. I don't know about the others, but the amount of challenges (math, physics and resources) to get this "simple" experiment up and running are huge, and it's very interesting to debate what's the best way to do all of that.

Hi, Darkstar. As I see it, the experiment was a POC and what Sandor is trying to do here, coming to this forum, is getting ideas and suggestions on how to get it right the next time. If the intentions are not these, then we are just wasting our time here (oh well, isn't that what an internet forum is all about anyway? ) If he is currently presenting the POC as "100% proof" of anything, he is only hurting his credibility, causing the next experiment to be taken less seriously, and the uphill battle to be harder. I see you bring a weight and lots of emotions from the 1000 posts in the other forum, but this forum is trying to be as fair as possible, given the information posted in this forum only. By saying that people here cannot see what are his beliefs, cannot see that the experiment was not accurate, cannot see that the data interpretation and presentation was biased, you are also saying that people here are clueless, what is kind of rude to be honest. People here are showing Sandor that the amount of calculations and advanced math and physics needed to get it right is much more than what was used in the POC, and this point is well understood, at least it seems so. You say: "Please consider beginning by trying to convince Sandor that just because a camera on the boat can SEE the laser looking back at the dock that this doesn't constitute a valid measurement of the beam center.". In this forum Sandor agreed a couple of times that the board needs to be improved for a second experiment, what seems to be an agreement that he understands that the estimation with the camera only is not enough. The possible misrepresentation of the LIDAR paper, the title of the video, their belief, etc, I believe are not part of the discussion. Worst case scenario, if people think he is not being honest, they will stop answering to the thread and it will be forgotten, right?

I saw the "trembling laser" video. That's a bizarre effect indeed. It looks like it's mainly going left to right only, but the light that is hitting the board is "dancing" in on itself. There is a big bright area (around 30cm wide I'd say), but there is also a huge area hitting the board that is even bigger than the board itself. Very intriguing. Do we have any optics nerd here in the forum? Regarding the beam distortions, those are a huge risk to your data set. If something like that happened during the night, there is no way to know what may have happened during the day. With this new information, I would say that you need to measure the beam spot every 100m or so. 500m may not be enough. It's too much refraction, reflection or whatever optic distortion is going on there, to guarantee the accuracy of the data. Different doubt though: you mentioned reflection, but that would mean that the laser hit the water at one point, is that correct? If that's the case, the laser was either pointing downwards or the crazy refraction effects forced it downwards. Are you taking notes of all Mordred's, Stu's, mine and others' suggestions? That's quite a lot

That's great. You should also seek the support of a good optical physicist. He can help you with the whole refraction and dispersion issues. As mentioned by Mordred, the more the better. You should have a static (in relation to the boat) camera pointing to the board. The camera on the shores are good only to "prove" that you are not fabricating data to the most skeptic ones, and you should keep using that. Your idea of an additional boat making extra measures is great, as you can keep one pilot in the "board boat" and the rest of the crew and measuring tools in the other boat. Regarding time and distance readings, the GPS and Clock from the camera at the "board boat" should be enough. Again, if you are concerned about proving to others that you are not fabricating data, just film and document the whole thing, like you did before. Double check all info before publishing to avoid misunderstandings. Finally, regarding the material - opaque or reflective - maybe you need additional POCs to find out what is better. What matters is that you should be able to clearly and easily find the limits of the beam spot. I think that measuring it after it went trough a semi-transparent material may cause small disruptions, but maybe I am being too cautious. I have no idea how it can move only sideways. Like I mentioned before, these refraction behavior that you saw there would be a very interesting paper all by itself Important to notice is that I think you saw that only during the night because it was more visible at that time. Maybe it was also happening during the day. Anyway, you need to find a way to control that, and if it's not possible to control, you will need to measure that. If this is happening, you will need your boat to be static (as much as possible) and measure several times during some 2min. We've been talking about measuring this or that, but I would say you need to document first and measure later. Mordred's suggestion of a "reference grid lines both horizontal and vertical" should be strongly considered. That's great that you have the resources. Consider the stabler boat you can find. Also, take Water and Air temperature readings with no movement from the boat. You shouldn't measure anything while the boat is moving, or you will need also to add all the speed and small inclinations to the board readings to the data set, adding unnecessary complexity. Finally, I don't think the board will be the best indicator for refraction. The board may help you with the refraction analysis, but it will not indicate the refraction all by itself. I didn't get this point exactly, sorry. You need a board that goes all the way from the bottom of the boat to 5m or 10m. You don't want to move the board up during the experiment (I didn't understand if that's what you want to do) or to have the board starting at 1.5m. And please go through Mordred list of suggestions in post #127, they are very very interesting. Thanks again for all the answers

Thanks again for the clarifications, Sandor. It's good to know that you want to enhance the experiment, that's always a good practice. Regarding the board, I wouldn't use a semi-transparent material anymore. This may be causing extra refraction and disrupting your data. I would suggest using an opaque material, taking the measures where the laser hits, and not on the other side. I would also strongly suggest you to not use any reflective material as a mean to capture the data. You want the light to be absorbed, not reflected. The reflective one is probably a good idea to help finding the beam, but not measuring it. I agree with your point that 3.45m - 1m is also not looking good for the GE model, but I was intrigued by the "moving laser" effect you mentioned. If a laser can move up to 2m left and right, I think it's possible it may be also moving up and down by the same amount. A well collimated laser (lets say 40cm at 5km) may cause the top and bottom limits of the laser to be 2.4m off, and a not well collimated laser (let's say 2m at 5km) may cause the top and bottom limits to be up to 4m off. I had no idea that this NUDTZ effect, like you call it, could have such a big impact. Very interesting. Only a quick correction, the beam center is always ~0 nm, not 1m. . But anyway, you need to be 100% sure about what the beam size and beam dispersion are. From the pictures you sent, I was making a wild estimation of 2.05m at 5km, but it could easily be 40cm or 4m, there is no way to tell. The images, as you mentioned, are from too far away. My suggestions, some of them already mentioned in the thread: Put your laser higher than 1.25m. The refraction at this height is causing too much variation to the data. Use a different board material, preferably opaque. Definitely a higher board. Do you think you can make it at least 5m? Can you get a bigger boat so that bigger structures can be mounted there? 10m would be cool Validate the beam dispersion. Measure the top and bottom of the laser spot at 10m, 100m, 500m, 1km, 2km. After that, you go back and start the experiment. This is only a calibration round. Same water and air temperature Perpendicular board as it's easier to measure heights. If possible, pre-mark the heights there so that you don't need to measure it during the experiment. More measuring: Top and Bottom of the laser spots every 500m. This will give you 24 measurements every time you run the experiment. Don't switch measuring tools (from board to jacket). I know it's too much to ask, but you have an uphill battle ahead of you.

Maybe it's happening? I don't know .... And I am silly, I always read NUDTZ and giggles because it looks like NUDEZ ... It's probably not helping my image here in this forum, but I am what I am. ;-)

So, it's like non-uniform-micro-refraction-artifacts that would cause the beam to change chaotically, making it impossible to predict the real direction of the beam? I think this concept is being used to try to explain why the beam is apparently bending upwards. It's interesting and would be a paper in itself. They should also explore that in the next experiment.

That's very interesting. So, disregarding refraction, with the point of view at 1.25m, everything higher than 55cm would be visible on the other side of the lake. Oh the power of math

Thanks for the reply, Sandor. I checked your online folder. In C2.jpg and C3.jpg you can see almost the whole circumference of the beam spot. I would estimate the diameter at around 20cm, maybe 30 cm at least as the top of the spot is not visible. That would mean a 20 cm minimum spread at 400m to 600m distance. Please let me know if I am wrong here as this is the basis for my whole analysis Image below is C2.jpg for reference. https://drive.google.com/file/d/0B2gyF12ygRBjZUhnMWRPZXhza2M/view?usp=sharing With a 0.08 mRad collimator, the expected diameter should be around 7cm to 8cm at 400m (I am estimating a 4cm initial beam size, again, let me know if I am wrong), but I can see it's a little bigger than that. I think the refraction is disrupting your beam a lot, or maybe the laser was not well calibrated. In the C18.jpg image you attached, the beam is not hitting the white board anymore, so we need to work with math only. With a 0.08mRad, at 5.038m distance, the spot diameter would be around 44cm. But at 400m, it looked like the spot was already at 20cm, so at 5km distance I would estimate it to be 205cm, or 2.05m. It's consistent with the animated gif you posted, as we can see the beam hitting the reflective jacket several times as the boat moves horizontally. The laser could be hitting the jacket anywhere in the 2m spot I think. With all that said, I am happy that you are planning to get a 0.003mRad collimated laser in the second experiment, but you need to make sure that it's well calibrated, as the 0.08 mRad you used in this first experiment was not doing well. Or if the disruption was caused by refraction only, this also needs to be taken care of.

What is a NUDTZ? I googled it and couldn't find any definition other than a small 3 lines Wiki article. Is it like refraction?

That's the main point. I want to understand how he measured beam height greater than 1.35m. His method is not specified. I also want to understand how he estimated the height of the beam as the spot size is getting bigger and bigger over distance. We are spending a lot of time discussing about possible reasons for the set of results, but I think the set of results are estimated, and not measured, at least taking into account what was shown in the video.

I can notice from your video in Youtube that your measuring white board is around 1.35m high. How did you take your measures starting in row 15 in your table as those are all higher than 1.35m? After 12min in your video the laser is not hitting the white board anymore ... I also noticed the beam diameter in the white board getting bigger and bigger. At around 14min the circle is nice and small. At around 19:10, the circle is barely recognizable. How did this "spread" impact your measures? How did you estimate the correct beam height as it was not nice and small anymore? Great structure you put there by the way.