@mightymoe You're right about the combined factor. Entering the SPC for PT into NCAT shows that the CSF shown on the bid plans is really the SF. El...

@mightymoe I hear you. I see stuff that doesn't compute every day and it's worse now that I've passed 80. But if the station numbering follows th...

@mightymoe lol! Thanks, Moe. I need something to do (you do agree that I don't have enough to do, right?) and l will give it a shot. You answered m...

@mightymoe So, in a table like the Little Coyote Road Centerline Alignment Coordinate Table here: SHEET2 the distanced between PT and PC stations ...

@mightymoe So, the distance between 25+30.3 and 29+30.3 is 400 feet, but that may not be a straight line distance, right.

@mightymoe I imagine that all SC surveyor's know it's meaning, but it's very unclear to outsiders. But help me understand something. Do alignment...

@lurker I found the explanation here on page 57. The coordinates are State Plane and if you want a distance, you have to calculate a combined facto...

Yeah, me neither. Here's a screen shot. Are the coordinates state plane or modified state plane?    

@mightymoe Yep, I spoke without thinking. The airport data above uses SP coordinates and ground distances, but I don't know of any DOTs that do. ...

@mightymoe Many highway surveys (I avoid railroads like the plague) specify SP coordinates and ground distances. As a surveying layman, that seems ...

@mightymoe When you calculate a single combined factor, you're still using state plane all of those feet underground. If you inverse between two po...

@lurker Yes. The simple geometry does reduce risk with acceptable error margins. Also, CAD is a productivity driver. In the old days, a project com...

@mightymoe We just matched a 7111-foot measured runway at 9000 feet elevation with a state plane calculation. We were able to do that because the c...

@mightymoe There is no error if you calculate grid distance and then adjust it by the combined factors at each end. That's what the airport example...

@boffc130 The math answer is that they are equivalent, so it doesn't matter which you choose. However, your original question seemed to be more abo...

@mightymoe indeed, if you expect grid to match ground. But why would anyone have that expectation given that the combined factor exists to match gr...

@mightymoe Wasn't the problem CAD's insistence on mathematical perfection? We still have that conflict but use least squares to satisfy CAD and exi...

Grid and ground produce great discussions. I have nothing to offer on how to survey, but I do have some insight into coordinate systems, so take this ...