IMPERIAL TO METRIC PROPERTIES

[cturlington]

Hello,

I am using Civil 3D 2014.

I have a file that was created from an Imperial template but the file since has been converted to a meteric file.  The coordinates and units are set to a metric setting.  I am taking length and areas of Autocad shapes by using the Properties dialog and cutting/pasting values into spreadsheet.  After realizing that all my Ambient Settings are still in imperial; after toggling these settings to metric ones, I noticed that my length and area properties values did not change, luckily.  The properties dialog does not show units, unfortunately, so I have assumed that the units are correct.  I just wanted to confirm that using the properties of AutoCAD shapes such as polylines and closed polyline shapes will give me the appropriate meters length and square meters area from a file that was converted to metric from imperial? 

[Anonymous]

Type Units and select Meters from the dialogue box that pops up. Additionally just switching the units to Metric in the Drawing Settings (in the settings toolbox) doesn't necessarily mean all the other settings will be in metric.

For example, the chainage displayed in a profile view can be changed to feet or meters Drawing Settings units is set to meters.

[cturlington]

So the AutoCAD Properties dialog reads the units established from the Units command?

[Jay_B · Accepted solution]

AutoCad simply uses the lengths & areas as drawn and the units are arbitrary to the program.

I rarely work with Meters anymore but whenever I do, I like to simplify and verify what's happening

with the units when converting the drawings.

.

Take an Imperial drawing and draw a closed polyline 10' x 10' = 100 ft2.

List the area in Properties which =100.

Now convert that drawing by changing the drawing settings units & zone tab Units on settings tab of toolspace to Meters.

List the area of closed Polyline again which still = 100.

No change.

In addition to changing the Units to Meters the Imperial drawing must also be scaled by a factor of .30480061 (conversion for US Survey Feet, International Foot is different) to have the areas report as Meters.

Once scaled by this factor now this same rectangle lists as 9.2903 m2.

9.2903 / .092903 (conversion for ft2 to m2) =100 verifying the conversion worked.

Hope that helps.

[AllenJessup · Accepted solution]

I don't recommend the use of UNITS in Civil 3D. I suggest AECDWGSETUP.

For conversion between Imperial and Metric I recommend using a Map Query for non-Civil 3D linework and export to LandXML then import to the Metric drawing for C3D objects including points. In the US I use Corpscon to convert the points externally.

The problem with scaling is that it isn't that simple when working in geospatial coordinate systems. It's OK if you're working in a local assumed net. Also if you are going to use scaling and don't have to change the original drawing. You're better off inserting a scaled Xref.

Allen

[Anonymous]

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@AllenJessup wrote:

I don't recommend the use of UNITS in Civil 3D. I suggest AECDWGSETUP.

[...] 

Allen

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Good morning,

Sorry about that, I wasn't aware of the AECDWGSETUP command. I rarely have to muck about with conversion as we don't have Clients that use feet.

[AllenJessup]

No worries. Since my state switched from Imperial to Metric and then back again. I have way too much experience.

Allen