COGO curve calculation

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T.M. Moretz
Posts: 79
Joined: Fri Nov 08, 2002 1:31 pm
Location: North Carolina, USA

COGO curve calculation

Post by T.M. Moretz » Sat Jan 24, 2004 5:29 am

I'm trying to draw on my screen a lot from a survey plat. The lot is located in the middle of a longer curve on a road R/W and in this case contains a
non-tangent, concave, counter clockwise curve. The COGO curve calculation routine offers the option of direction to radius or use an existing radius point and as of now I have neither. I'm not even sure how to calculate the direction to this radius but even if I could it seems that being able to enter the chord direction and then entering one of the elements of the curve as a negitive, if necessary, would solve my problem. How have the rest of you been handling this and am I missing something obvious? Thanks, Ted.

Posts: 299
Joined: Sun Nov 10, 2002 6:41 am
Location: Peterborough, Ontario, Canada

Post by rwhatman » Sat Jan 24, 2004 6:30 am

This may not be helpful, but here goes.

I have not use Cogo in years. I draw the problem.

The key word you use was non-tangental curve. If your not
given enough data from the survey plate you won't get it.

Now say I am given just a radius I can do it.

Just draw the lot lines first then you have the two ends of the
the curve. All you have to do is draw a arc between them.

If they give you arc or chord you can check the new arc.

I do use Cogo a little, but only for editing. Now that we can store
and rerun the Cogo I should use it more.

After you have the lines are drawn you can easily put points on them.

I wished I could help you more with your Cogo. Richard

Glen Cameron
Posts: 1395
Joined: Fri Nov 08, 2002 12:18 pm
Location: Corbeil, Ontario, Canada

Chord Bearing

Post by Glen Cameron » Sat Jan 24, 2004 8:58 am

If you have MSCAD2002 SP#4 then you do have a Chord Bearing option in COGO to enter in your curve info.

When you run COGO, on the option bar you will see a button with CB on it. Or you can type in CB at the Enter From Point prompt.

Below is a short example that I just ran here on my machine:

> cogo
Inverse:Pt..Pt/Curve Inverse:Pt..Pt..Pt
Enter From Point: <84>CB

Enter From Point (chord) <84>: Point
Pick the point:

Point 3 found...
Options: +/- or Pt..Pt+-Angle
Enter Quadrant Bearing like QDD.MMSS (chord): 145.
Options: C#=-*/sin/cos/tan... or Pt..Pt(+-*/) a Distance
Enter the Distance (chord): 200

Enter To Point (chord) <86>: 500

Enter Description (chord end pt):

Curve information type <R>:
Options: C#=-*/sin/cos/tan... or Pt..Pt(+-*/) a Distance
Enter radius: 500

Curve direction (- left, + right):+

Enter radial pt num: <87>: 501

Enter Description (rad pt):

3 N45°00'00"E 400.000 271.595 257.963 500
Arc: 201.358 Chord: 200.000 Tangent: 102.062 Delta: 23.0426 Radius: 500.000
Inverse:Pt..Pt/Curve Inverse:Pt..Pt..Pt
Enter From Point: <500>*** Cancel ***

Glen W. Cameron, C.E.T.
City of North Bay, Ontario

T.M. Moretz
Posts: 79
Joined: Fri Nov 08, 2002 1:31 pm
Location: North Carolina, USA


Post by T.M. Moretz » Sun Jan 25, 2004 7:59 am

Richard, I could have done it that way and I have done it that way in the past, almost exclusively, but I have decided that always using CAD in this way has made me COGO "soft". There have been times in the field when I've been trying to calculate an offset line or a curve (something I could do blindfolded in the past) and realize that I've lost my touch because I've gotten used to doing it graphically in the office with CAD and then just assigning point numbers. I find this to be one of the great advantages and potential pitfalls of CAD. If I had had to rely on this method I wouldn't have been able to pass my surveyor's exam. I just need to resharpen my COGO skills.
Glen, once again you have pointed out the obvious to me. I need to lose this tunnel vision when using this software. Thanks, Ted

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