Recreate Arc from notations displayed in raster

[PSAPmapR]

Greetings All,

 

First off, I'm a GIS user using AutoCAD (self taught) to supplement my work, I'm running AC 2005 (plain vanilla, no add ons).

 

I am attempting to digitize from a raster I have attached to my drawing. The image is scaled and rotated appropriately. However, I'm at a loss at how to recreate an arc where RADIUS, ARCH and CHORD are given. I hope to attach a screen shot below to better illustrate my question, and that is, how do I re-create this rascal in AutoCAD? The line (arc) I am trying to re-create is circled in yellow.

 

Many many thanks in advance if you can help.

Dave

[CyberAngel]

The simplest way, I believe, is to use the Arc command. Give it the starting point at one end. Specify the End option for the next point (the other end). Specify the R option for radius and type in the radius. If the arc is concave instead of convex (or vice versa), undo the first command and do it over with a negative radius. How you'd be able to tell that by looking at it, I don't know.

[PSAPmapR]

Thanks Angel, I'm presuming that the bearings shown above the annotation (and on the dashed line representing the survey line) is the same bearing for the CHORD, just prior to your email, I had tested this using that bearing for the CHORD, the distance of the CHORD and with some AC construction lines and great big circle going the long way about it, appears your solution matches (or the other way around

 

Thanks a lot, in the future, I'll know to simply get the distance and bearing of the chord, and using your "falling off a log" simple solution, this should be a painless endeavor next time

 

Dave

"Remember, wherever you go... there you are"

[JD Mather]

Notice that the Chord Length and Arc Length are almost identical.

The arc is close to being a straight line.

 

Oops, I should have changed the precision for angle display that 4 is actually 4.0575

Edited October 31, 2011 by JD Mather

[PSAPmapR]

The arc is close to being a straight line.

 

Indeed, in that, my "elemnetary" discovery produces the same result as CyberAngel's recommendation of using the ARC command... the CHORD depth is but a hair over 3.8 feet.

[JD Mather]

I am using a later version of AutoCAD with a parametric solution - I type in the knowns - AutoCAD draws the correct arc.

In your version you could draw a circle with R6157.78

Draw a line from center to arc.

Copy and Rotate line by 4.05746398° and trim the arc. This gives draw line from end to end of arc.

This gives you your arc length and chord.

Use Align command to align the endpoints of the arc to the rest of your geometry.

 

(another option would be Measure to get the arc length)

[alanjt]

You have the chord bearing, chord distance and radius. Based on the other calls, it appears to be concaving south. Draw a line in at the chord bearing and distance @435.78

eg.

Command: a
ARC Specify start point of arc or [Center]:
Specify second point of arc or [Center/End]: e
Specify end point of arc:
Specify center point of arc or [Angle/Direction/Radius]: r
Specify radius of arc: 435.98

 

Once arc is drawn in, erase line. You need the line first to get the proper direction.

[cadvision]

check out WiseImage from www.csoft.com if you are going to deal with raster images alot.

[Murph_map]

Greetings All,

 

First off, I'm a GIS user using AutoCAD

 

Nothing wrong with that, You may want to take a look at AutoCAD MAP3D