wandererfan wrote: ↑Sun Dec 02, 2018 2:20 pm
Are these the right units?
Length: "ft"
Area: "ft^2"
Volume: "ft^3"
Mass: "lb"
Pressure: "psi"
Velocity: "ft/sec"
Angle: "°" (grad?)
Oh, man. That looks great! For what I need at the moment, it'll work fine.
It occurred to me, though, that maybe I should take the opportunity to spell out what's really needed for a transportation-specific unit system. I didn't want to get deep in the weeds on this until I really had something that made doing it worthwhile, but here goes, anyway.
1. Velocity should be MPH, since the only time it's used is to talk about the speed of planes, trains, and automobiles..
2. Mass and volume units vary depending on what's being described, with mass being either lbs or tons, and volume being either cu.ft. or cu.yd. The default foot / pound is certainly fine.
3. We actually measure angles in degrees, minutes, and seconds (DMS), rather than decimal degrees - didn't think of that until just now! I don't know about the metric side, but I don't think we ever used gradians / radians unless it's deep into surveying-specific applications... Anyway, a minute = 1/60th of a degree and a second is 1/3600th of a degree, same concept as time.
4. I could display DMS units as a 3D vector in the properties view, I guess, though it's somewhat inelegant. We use angles primarily as a bearing from true north. The number format is ddd°mm' ss", though that often gets decorated with NE, NW, SE, SW to indicate the quadrant, which keeps the angles in the 0-90 degree range. Thus, 340 degrees would be N70°00'00"W. Likewise, 120 degrees would be S30°00'00"E.
5. We also use of stationing in transportation engineering to describe length / position. A station is really just the distance along an alignment (usually the roadway center line) in feet / meters, but formatted differently. In feet, 1 station = 100 feet. In metric, 1 station = 1,000 meters. The location of everything that exists in a highway construction project between the beginning and ending points is described using stationing.
For example, let's say I'm standing along a highway 10,528.77 feet from the start of a project. In English, I'm 105.2877 stations from the starting point. In metric, it's 3.210 stations. (10528.77 / 3.28 = 3210.00, rounding up).
More commonly I'd refer to the Station proper and say I'm at "Station 105+28.77" or "Station 3+210.00" (I'm a bit sketchy on precision in metric...). In fact, I can use it to locate myself in two dimensions, and I can say I'm at "Station 105+28.77, 20.50' LT". In other words, I'm standing 20.5 feet to the left of the alignment / center line of the road. Note that left (LT) and right (RT) are determined by the direction in which stationing increases along the alignment.
Anyway, sorry for getting so complicated. The conversions aren't complex, it's just a lot of discipline-specific unit notation that's persisted for a couple of centuries that's the hassle...
FreeCAD
