Simple, well expressed informative. Excellent. I wish more YT information videos were presented with this degree of focus on the message, rather than the presenter.
Dear Tod Sir ... thank you & in the hindsight the Surveyors Association. RU-vid can't be better than this. A similar uploads on "Total Stations" would be helpful. GBU Sir !!.
Sir i dont know you but i am very much thankful to you as during my graduation time no one taught us about levelling the way you taught amazing short and valuable videos thankyou sir for making such nice videos thanks alot once again
In the UK, we call the horizontal plane swept out by the instrument "the plane of collimation" and, of course, we don't use staves in foot/inch measurements but the normal metric "E" staff in which each "E" is 50mm high with 10mm thickness of the three arms of the "E". The next 50mm is three blocks of 10mm depth, spaced 10mm apart. The whole thing is then repeated on the next 100mm or 1/10 of a metre. Then the metre figure is marked and in the next metre, the "E"s are on the other side of staff face and so on.
Calibrated, older style dumpy levels can be just as accurate in the field for measuring elevations as automatic levels. Automatic levels though take much of the human error out of the picture, as the compensator has a big working range that keeps the hz line of sight true. The part of your video where you're showing the circular bubble moving straight back and forth in and out of the bullseye is how you test the repeatability of a compensator to maintain a level line of sight. So, when an operator is using one of these instruments in the field, if the compensator is working and repeating as it should, typically anywhere within the bullseye is level enough. The compensator does have limits, but they are typically way outside the bullseye straight back and forth as again you showed on your video. So, the ease of use is a big reason why they are so accurate in the field as they eliminate much of the human error you would have with leveling error associated with traditional dumpy-type levels. The difference in accuracy is huge between a circular bubble on an automatic level and a higher precision vial on a dumpy level. But, the automatic level bubble only has to be so accurate as the all the leveling accuracy of the instrument is delivered through the function of the compensator. A dumpy level vial like the one in your video is like a 20-30 second bubble which of course translates to how level the instrument is in actually 4 directions, not just 2. And, of course this translates to the dumpy levels accuracy for measuring elevations. Both instruments are calibrated to repeat within a few arc seconds in a survey instrument repair shop's collimator. The automatic level though simply through it's design and ease of use delivers more consistent accuracy over the long run. It's still the gold standard for measuring elevations in the field at +/- 1/32" per 100 ft., with a calibrated instrument. Laser levels are more like +/- 1/8" per 100', and have some operator error introduced into the picture with how the operator goes about using the laser receiver.
@@jayadams35 no, I meant it as a joke! But we have found that long occupation static GPS obs give fantastic results when used in conjuction with a reliable geoid. In one case over 10km the GPS and leveling differed by only 6mm.
There is only one comment I have to make. When Todd is explaining rise/run, he suggests a layman should measure the distance between the two points. If the is measured along the ground, it would be the hypotenuse of the triangle. It must be the horizontal distance, aka the run. An example of this, if you have a 45 degree slope and measure the slope distance between two points, say 100 feet apart horizontally, you will measure 141 feet, the sine or cosine of 45 degrees along the slope. Other than this, this was a good video. Please note, that land surveyors measure the horizontal distances for land surveys, therefore, you could call them “flat-earthers”.
You don't calculate angles with a theodolite, you measure them, both horizontal and vertical. That is what a theodolite is for. You can then do the calculations back in the office with a computer, pocket calculator, slide rule or book of log tables using the angles you have measured with the theodolite.
If you plot a plane that’s perfectly perpendicular to plumb on the shore of a 10 mile wide lake. How much will the center of the water deviate from the objectively level plane?
The center of the water will not deviate from the objectively level plane. This is because a plumb line, used to determine verticality, is perpendicular to the surface of the water. Therefore, a plane that is perfectly perpendicular to plumb will also be parallel to the surface of the water in the lake.
Nothing is 100% perfect in this world but errors must not be fatal even when they are accomulated yet again all professional errors must be field specific depending on what you are measuring and for that purpose (negligible error).
So, level is horizontal. 3:12 3:37-so horizontal is gravity? Why not just say perpendicular to horizontal? 7:30- so if you can extend the horizontal line, at which point does one differentiate between elevation and earth curve?
1. One word can have different meanings in different contexts, in that case indeed, because he meant a fictional straight line at the level of that tripod. 2. Because in that context it's synonymous, horizontal at coordinates where that guy was standing, or any coordinates is perpendicular to the direction of gravity in that place. 3. There isn't a magical border up to which it doesn't differentiate and then it drops drastically, it does it continuously at very small rate, so it can be ignored until you're surveing terrain for few kilometers long bridge or something, for example the joined effect of refraction and curvature at the distance of 400m isn't greater than 1cm.
Would you kindly do a video of measuring the curvature of the Earth, to put the flat Earth theory to rest.. I posit that could be done with two theodolites. The second, place at a distance acceptable for the optics and accuracy, would have it's orifice centered by the first theodolite. The second shooting back at the first should strike above the orifice of the first by double the calculated curvature, which is 1.5 thousandths of an inch per linear foot distance. The curvature would be quite easy to see as this method would accurately double the measurement. Thank you from New Zealand.
Because with this method you would have to run with that level from place to place and do that insane ammount of times at bigger distances to cover it, when with laser level you can do that with one measurement.
You say at the start that measuring the horizontal distance is "easy" and one can use a tape measure. How is it easy to measure the horizontal distance, of say, 100m with a tape measure? I would say that was impossible.
@@smith-mundtnews1406 If you define "level" as perpendicular to the direction on gravitational pull, then you're absolutely right. The "must be contained" part is absolutely meaningless, it must be contained to not do what? Disappear from the existence? I can pour out a glass of water on my floor right now and it's still here, so I don't really know what you're trying to communicate here. Just blindly repeating the same meaningless mantra all flerfs say, for "free thinkers" who aren't "sheep" you surely like to say the same exact things 🤔
