We have a review comment on a survey that the radius used to calc a curve was wrong. The curve information was given as Darc=12 00 R=477.5 so I had calc'd the curve with a 477.50 radius. Now the reviewer is saying that the radius used should have been 5729.65/12 or 477.47' . I see that 5730/12 = 477.5 which is where I think the 477.5 comes from (this is from a 1949 highway map). Which radius is the correct one? I'm willing to concede that 477.47' might be technically correct but how many surveyors would bother to calc the radius vs just use the printed number?
Check this [msg=54075]Thread[/msg].
In the days of slide rules and trig/log tables, 477.5' was most likely the value used for the radius; in this day and age with super-whiz-bang calculators and computers, 477.464829276' would probably be used.
In my opinion, I believe you are using historically correct data in your calc's and should hold. Just my opinion.
The only superior evidence is that which you haven't yet found.
They would have rounded to the nearest tenth back in the day anyway. This guy is arguing exact calculations on a road right-of-way that wasn't staked out to that precision. (by the way, the chord-distance you would pull for every 100' of arc would be the same number to the nearest hundredth using either radius value. (99.82 I get)
I might use my calculated radius, or maybe just what is "given". The fact is we are arguing minutia over something ran 65 years ago.
Thanks to Mike Bend. That is an excellent thread. Thank you Doug for linking it.
for starters- the proper constant is 5729.58 -> (5729.578) -> (180/pi*100), not 5729.65-
otherwise- see the thread-