RE: VW 10.1.0, Win XP
I have used AUTOCAD to do 2D coordinate geometry (COGO) for land surveying. I HAD hoped to do the same with VW. But... VW does something bad, approximate and irritating that makes it useless for COGO. It makes terrible round-off errors.
I've got all snaps off, linear and angular "units" set to maximum accuracy (lotsa
zeros). I've set angular units to "degrees, minutes and seconds.
Say I want to draw a line of a certain length, at
a certain angle (a very basic thing to do in
land surveying, it's called a one course of a
traverse -- a traverse typically containing
dozens of courses)
Hit the line tool. Click the mouse anywhere on
the screen. The beginning point of a line is set.
Now set the angle:
Tab over to the angle entry box box on the data display bar. Enter "-89d59m26s" in the angle entry box. Hit return. Angle Data is accepted
correctly.
Now to set the length:
Tab over to the "L:" (length entry) box on the
data display bar. Enter "30.00000" Thus far, so good. Hit the return key. DATA IS NOT ACCEPTED CORRECTLY !!
Upon hitting the return key, the "30.00000" is CHANGED by VW to "30.0117235714" !!! (This also
is what shows up in the object info palette).
Now, look, I just SPECIFIED 30.00000 -- what gives with VW throwing in an additional 0.0117235714 ? A rounding error of 1 in 3000 is
NOT GOOD !!!!
Interestingly, if I key in the same angle, but
change the length from 30.00000 to 3000.000 --
VW STILL changes the length I entered from 3000 to 3000.000177649 - an acceptable degree of rounding error 1 part in 30 million or so.
I also note that, depending upon the initial point of the line, VW gives me back slightly
different answers.
I also note that no matter what I do up in the
data display bar, I can't keep VW from CHANGING
the entered data and I can't get it to leave
my length of 30.00000 ALONE. Plus, while I can't
get the data display bar to accept 30.00000, I
CAN, once the object is entered, go to the object
info palette, set how it displays a line object
info to "angle and length" and change the funky 30.0117235714 BACK to 30.00000.
What is going on? Is there ANOTHER "units" or round-off parameter to VW I can set to get more
numerical accuracy?