Distance measurement Definition and 19 Threads

Length measurement, distance measurement, or range measurement (ranging) refers to the many ways in which length, distance, or range can be measured. The most commonly used approaches are the rulers, followed by transit-time methods and the interferometer methods based upon the speed of light.
For objects such as crystals and diffraction gratings, diffraction is used with X-rays and electron beams. Measurement techniques for three-dimensional structures very small in every dimension use specialized instruments such as ion microscopy coupled with intensive computer modeling.

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  1. F

    I Uncertainties accumulate when measuring longer lengths?

    Hello, It is clear that as distance being measured increases, more graduations are needed to represent a unit of measure for such distance. Each graduation in a measuring device is subject to uncertainty and error, and these errors and uncertainties accumulate with the increase in the number of...
  2. F

    I Looking for the most suitable distance for binary clustering

    Hello everyone. I have a pandas dataset in python which has n+1 columns and t rows. The first column is a timestamp that goes second by second during a time interval, and the other columns are the names of the people who log in the server. The t rows of the other columns indicate if the person...
  3. mncyapntsi

    Intro Physics homework help - distance and velocity

    I have tried this problem over 4 times and keep getting the exact same answer, which is incorrect. Could someone please help by pointing out what I did wrong, or letting me know if I am actually on the completely wrong path? Thanks! Have a wonderful day :)
  4. A

    I CMB creation, distance measurement question

    How do we know it;s redshift for certain? because unlike with stars the CMB doesn't have spectral lines nor other "similar" objects to compare to as it is everywhere and the same. From what I understand first came the theory and model of the Big bang, then Hubble saw that distant galaxies are...
  5. T

    A How much does peculiar velocity affect distance measurement?

    I'm a PhD student who's taken GR, so I have studied gravity and cosmology, and we have the underlying assumption of homogeneity and isotropy, but since this assumption comes from how we've calculated the distribution of galaxies in the visible universe I want to make sure I really understand it...
  6. S

    Non-coherent spread spectrum for distance measurement

    Hi,I’ve heard of a technology that enables to measure the distance of a satellite to the ground station by using non-coherent spread spectrum. Can anybody tell me what’s the name of this technology?Senmeis
  7. F

    A A question about coordinate distance & geometrical distance

    As I understand it, the notion of a distance between points on a manifold ##M## requires that the manifold be endowed with a metric ##g##. In the case of ordinary Euclidean space this is simply the trivial identity matrix, i.e. ##g_{\mu\nu}=\delta_{\mu\nu}##. In Euclidean space we also have that...
  8. C

    Camera which measures distance?

    Hi all, I'm having trouble finding something online which isn't a very complicated device, but I don't know if it has a specific name, which would help me in a google search. I have a motor in an MBE which moves the sample, and I need a camera which can read to a computer what the distance is...
  9. T

    Measuring aperture size through Lumen intensity -- Advice.please

    Greetings everyone. I'm working on a project that requires the very accurate measurement of distance varying between 0.500'' and 0.050''. I need to measure the distance within at most 0.010'' tolerance and give the value digitally. The read-rate is once every second. I'm on a very tight budget...
  10. R

    What methods are used to measure cosmic distances?

    How do astronomers measure cosmic distance, say 7 billion light-years? http://www.space.com/17399-gamma-ray-photons-quantum-spacetime.html
  11. N

    Light Years: Subjectivity and Distance Measurement

    Light years-I just don't understand how something as subjective as visibilty, is used as a major indicator of distance. Isnt that subjective. What if some species had a million times the eye power than us humans, wouldn't they view the distance of let's say stars very differently because it...
  12. S

    Measuring Distance on a Cylinder - Ideas & Opinions Wanted

    Hi all I have assigned a task to measure distance at two points separated 200 mm apart on a cylinder having diameter about 300 mm dia. The distance from point and measuring point will be 150 mm and that of for second point will be 150.05mm.I have an idea of using two lasers mounted 200 mm...
  13. ¡

    RF Distance Measurement Techniques (ToF+Interferometry)

    I am trying to design a system to measure the distance between two RF transceivers with as small of a resolution as possible. Time-of-flight measurement is nice and easy to do, but it has a poor resolution with low frequency timers. I am thinking of using a low-cost mcu that will probably have a...
  14. I

    Distance measurement by means of optical interferometry

    Hi, I have been assigned to a new task in my job where I have to investigate on measuring the distance to an object by means of optical interferometry (Michelson interferometry). I have been looking for info on the subject but have not been really lucky. I have been able to obtain the...
  15. N

    Ultrasonic in distance measurement

    Hi tehre, this is my firs post here! I'm designing a complex system using a 40kHz ultrasonic transducers in distance measurement for waste container level detection. Now I have a big problem because the hot season change the air properties in temperature and humidity. Anyone may help me...
  16. R

    Ultrasonic distance measurement and ghost echoes

    hi everyone, while doing a project on ultrasonic distance measurement, i came across the phenomenon of ghost echoes. The ultrasonic waves are emitted and made to reflect on a surface( of which the distance to the source is to be found). This reflected waves are detected, and time for b/w the...
  17. P

    Basic Time and Distance Measurement Help

    Vroom-vroom! As soon as a traffic light turns green, a car speeds up from rest to 50.0 mi/h with a constant acceleration of 8.60 mi/hs. In the adjoining bike lane, a cyclist speeds up from rest to 20.0 mi/h with a constant acceleration of 14.5 mi/hs. Each vehicle maintains a constant velocity...
  18. S

    Measuring Distances in Microns/Nanometers for Small Objects

    How are distances on the order of microns or nanometers measured for objects like say a bacteria or a very small component of a device where distance measurement through interference of light isn't very feasible?
  19. C

    Distance measurement with laser

    How would go about measuring distance with a laser? I'd like to construct a zero-contact method of measuring distance much like the commercial units designed to allow digitizing of a model as a retrofit on a 3-axis CNC. My understanding is that they position the X-Y and then determine the Z...
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