Dimensioning a Drawing - AutoCAD 2011 and AutoCAD LT 2011: No Experience Required - page 632

8. Click the Ordinate button on the drop-down menu on the
Dimensions panel.
9. Click the upper-left corner of the rectangular plate, and then move
the cursor straight up above the point you picked. When you're about
an inch above the plate, click again.
This sets the first ordinate dimension (see the top of Figure 12.41).
10. Press the spacebar to repeat the DIMORDINATE command. Then repeat
step 9 for the four circles near the middle or upper portions of the plate,
using their centers as points to snap to and aligning the ordinate dimen-
sions by eye.
The lower circle is in vertical alignment with the one above it, so it
needs no horizontal dimension. Place an ordinate dimension on the
upper-right corner of the plate to finish. Press the F8 key to toggle
Ortho mode off if you need to jog an extension line. The result should
look like the middle image of Figure 12.41.
11. Repeat this procedure for the y-ordinate dimensions. Once again, ignore
any circles that are in vertical alignment, but include the upper-left and
lower-left corners of the plate (see the bottom of Figure 12.41).
The civil engineering discipline typically uses a different type of ordinate
dimensions. A datum reference point is used, but the dimensions are displayed
at each point in a format typically referred to as northing and easting. Using
this format, the y-coordinate is displayed first as the northing location, and
separated by a comma, the x-coordinate is displayed as the easting location,
as shown in Figure 12.42. Because of this special format, most civil engineers
choose a product like AutoCAD Civil 3D that has specialized tools for generating
ordinate dimensions in this format.
When you change settings for a dimension style, dimensions created when that
style was current will automatically update to reflect the changes. You'll modify
more dimensions in the next section.
You have been introduced to the basic types of dimensions (linear, radial, leader,
and angular) and some auxiliary dimensions (baseline, continue, and aligned) that
are special cases of the linear type. You can also use the baseline and continuous
dimensions with angular dimensions.
Feel free to save the drawing file you created working through the last several
exercises to refer back to later. For the purposes of this topic, we will not use this
specific file again so you can close your drawing without saving the changes.