Quentin
QUOTE: Originally posted by Hugh Jampton Well that doesn't seem logical to me. Surveyors measure the distance from the theolodite to the measuring stick along the ground (the hypotenuse) [they used to use a 66' chain] and sight to the height on the measuring stick (the opposite side), which makes the sin easier to calculate. To calculate the tangent they would have to mesure the distance from the theolodite to the measuring stick exactly horizontal (the adjacent side), which seems a load of hassle because of sag in the line and the difficulty of getting it level [perhaps nowadays laser measuring equipment does this simply, but railroads were built before the advent of these]. I'm not a surveyor, but I know some, and I'll certainly ask next time I see them, but if I were going to do it I'd certainly opt for the easy method.
QUOTE: Originally posted by ajmiller I didn't know what a theolodite was, but when I looked it up online, it asked me if I ment theodolite which is defined as: a surveying instrument for measuring horizontal and vertical angles, consisting of a small telescope mounted on a tripod. It's a synonym of transit. I always thought that transit was a strange name since to me transit means transportation system.
Dave H. Painted side goes up. My website : wnbranch.com
QUOTE: Originally posted by tree68 Boy - we better not get into degrees of curvature....
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
QUOTE: Originally posted by Modelcar ...Let me take a new stab at our question...with this data. That being: "How does one relate a % grade to an angle in degrees".... * A 45 degree slope is a 100% grade. Us 45 as your constant and multiply by percent grade expressed as a decimal. Example: Convert a 20% slope to degrees 45 degrees times .20 = 9 degrees. Example: Convert a 9 degree slope to a percent. 9 degree / 45 = .2 = 20%
QUOTE: Originally posted by ajmiller If the formula is sin A = grade percentage / 100, then a 100% grade gives an angle A = arcsin(100/100) = arcsin(1) = 90 degrees. So would a 1% grade be one foot increase in elevation for every 100 feet of horizontal distance, or one foot increase in elevation for every 100 linear feet of track? At small angles there's not much difference. The first definition implies that A = arctan(percent grade/100) and the second implies that A = arcsin(percent grade/100).
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