Datasheet

WINDOWS ON THE MODEL

Figure 1.5

Drawing Settings

dialog

Units And Zone Tab

The Units And Zone tab lets you specify metric or imperial units, as well as control the assumed

plotting scale of the drawing. The drawing units typically come from a template, but the options for

scaling blocks and setting AutoCAD variables depend on your working environment. Many engi-

neers continue to work in an arbitrary coordinate system using the settings as shown earlier, but

using a real coordinate system is easy! For example, setting up a drawing for the Dallas, Texas, area,

you’d follow this procedure:

Select USA Texas from the Categories dropdown menu on the Units And Zone tab.

Select NAD83 Texas State Planes, North Central Zone, US Foot from the Available

Coordinate Systems dropdown menu.

There are literally hundreds, if not thousands, of available coordinate systems. These are estab-

lished by international agreement and because Civil 3D is a worldwide product, almost any recog-

nized surveying coordinate system can be found in the options here. Once your coordinate system

has been established, you can change it on the Transformation tab if desired.

Transformation Tab

With a base coordinate system selected, you can now do any further refinement you’d like using

the Transformation tab. The coordinate systems on the Units And Zone tab can be refined to meet

local ordinances, tie in with historical data, or account for minor changes in methodology. These

changes can include the following:

Apply Sea Level Scale Factor

which that takes into account the mean elevation of the site and

the spheroid radius that is currently being applied as a function of the selected zone ellipsoid.

Grid Scale Factor

, which is based on a 1:1 value, a user-defined uniform scale factor, a reference

point scaling, or a prismoidal transformation in which every point in the grid is adjusted by a

unique amount.

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