Ma Be wrote: >Hmm... Do I sense some... confusion here? >One side is saying it's the tangent, the other it's the sine.
No confusion. I am just stating UK practice. See the three measures in parallel at: www.planning.odpm.gov.uk/mpg/mpg7/05.htm See the following definition (although it is capable of misinterpretation): www.scotland.gov.uk/consultations/transport/rcmf-07.asp Some maps indicate road gradient by symbol. Examples are in one of the links I posted before. As Joseph suggests, without symbols, it is easier to calculate tangent than sine. For small angles, sine approximates tangent. Gradients of up to 14% (1 in 7 or 8 degrees) give about the same results whether calculated with sine or tangent. A determined google search indicates that US terminology is identical to UK. See the following US government pages: http://newton.dep.anl.gov/askasci/gen99/gen99425.htm http://draco.acs.uci.edu/rbfaq/FAQ/9.3.html (beware of URL line wrap)
