Post by aliveandkicking on Apr 17, 2015 5:41:57 GMT
I have just been learning that surveyors of large projects must take into account the curvature of the Earth and refraction in air along the line of sight where the refraction error can be safely assumed to be 1/7 of the curvature error. At a 5 mile distance the elevation error caused by curvature is over 14 feet. Such a very large error could make a canal or drainage project an embarassing failure. On smaller distances curvature can be ignored. The curvature error over a 300 foot distance is only 0.002 of a foot.
Today surveyors can use speed of light to measure distance over 50km at +/- 10mm accuracy. Angle and distance can be known so accurately that mm deformation of the earths crust can be measured automatically by vulcanologists with minimal surveying abilities using automatic stations with the results emailed automatically to their offices.
Additionally below survey heights of 2m, temperature at the ground can create errors for large distances due to the effect of temperature upon refraction of the air.
Refraction error means we see more of the horizon than without it. If refraction error was the same as curvature error we would not see objects dip below the horizon.
Surveying instruments have been so accurate for many decades that when surveying large projects, if the Earth was flat all of these surveyors and equipment manufacturers would have to know the Earth was flat and be part of a conspiracy.
In principle though it would be simple for somebody not in the industry to make their own measurements.
Today surveyors can use speed of light to measure distance over 50km at +/- 10mm accuracy. Angle and distance can be known so accurately that mm deformation of the earths crust can be measured automatically by vulcanologists with minimal surveying abilities using automatic stations with the results emailed automatically to their offices.
Additionally below survey heights of 2m, temperature at the ground can create errors for large distances due to the effect of temperature upon refraction of the air.
Refraction error means we see more of the horizon than without it. If refraction error was the same as curvature error we would not see objects dip below the horizon.
Surveying instruments have been so accurate for many decades that when surveying large projects, if the Earth was flat all of these surveyors and equipment manufacturers would have to know the Earth was flat and be part of a conspiracy.
In principle though it would be simple for somebody not in the industry to make their own measurements.
