Create Circle Polygon to measure diameter

[JoshuaSoble]

hello- this seems to be a rather elementary, but I've been having a ton of trouble with this.

I want to make polygon features that are perfect circles so that I can measure their diameter. If I use the the Arctool in Editor, I cannot produce perfect circles. So after I make the circle polygons, I will have to also measure their diameter.

Any ideas?  thanks

josh

ps- sorry if I posted this in the wrong place. i'm a little new here...

[HardolphWasteneys]

Try the following:

1. In an edit session activate "snapping" on vertices for a polyline FC.
2. start with a polyline from the spot you want as the centre of your circle and right click to get the menu and choose "length"; input the radius of the circle you want. Left click and hit F2 to "finish sketch"
3. In the "Advanced Editiing" toolbar select the circle tool.
4. snap to the center point of the radial line and trace along the line to expand the circle until you snap to the end point of the line.  left click

5. and alternative is to just use the advanced editing circle, and hit the "r" key once you start drawing and input the radius.

That's your circle with a defined diameter and position.

Hardolph

[JoshuaSoble]

thanks for the reply. Unfortunately, I'm trying to measure the diameter of circles already in an image rather than produce circles with a predetermined diameter.

I've jsut resorted to drawing a polyline across the image and using the surface length tool to measure the length of the line as the diameter. I'm still a little hesitant though because by doing it by hand, I don't guarantee that my diameter line is going directly through the circle center.

but it'll have to do for now.

thanks for the help.

josh

[StefanHaglund]

Hi Josh,

Seems like you could use the field calculator to do this on your pre-existing circles. If your circles (polygons) are in a geodatabase you'll find the area in the shape_area field. Add a new field (Double) and do the math to get the diameter.

If they are shapefiles, either export them to a gdb or use calculate the area with the field calculator.

Cheers,
Stefan