Linework Code Sets

[wrmurphy81]

Can someone explain the deal with curves and survey figures? I have experimented with the BC, OC, and EC codes and I feel like we are taking too many shots.

 

I am used to starting a line (or figure as C3D calls it) and code everything with the same code (i.e. "EP" for edge of pavement) until I come to a curve. At the point of curvature I would take an EP shot, then the next shot (on curvature) would be called EP OC, then the next shot (end of curvature) would be EP again. But this doesn't always work with C3D.

 

I have found a fix by calling the point of curvature shot EP BC, then the on curve shot EP OC, the last shot on the curve would be EP EC. This is cool with me, but the problem is when I run into a compound curve or reverse curve because I have to take two shots at the same point... one shot ending the first curve and the second shot begins the second curve.

 

Anybody have any insight? I hope this makes sense... my wife tells me every day that I don't communicate clearly.

[sinc]

The OC command is designed to be used as the third shot in a series of five shots. The first two shots define the incoming tangent, and the last two shots define the outgoing tangent. C3D will create a curve between those two tangents that goes through your OC shot.

 

If you have a reverse curve, easiest thing is to just use a BC at the beginning of the first curve, then an EC at the end of the final curve. You should not use OC for this. C3D will automatically create the reverse curve.

 

Here's some examples. In the example below, figure EOA4 gives an error:

Figure EOA4 curve beginning at point 1025 - Curve fit failed.

Cannot create a one point curve without leading and trailing tangents.

The rest of the figures form nicely.

 

[wrmurphy81]

Thanks, Sinc. The tangent bit was throwing me off. The multiple OC shots in compound curves is going to be a really nice feature.