Buffer Beware

Those that are taking advance of the buffer tool in AutoCAD MAP 3D 2008 beware. If you fail to set a coordinate system in your drawing you may end up with a buffer in METERS even when you select FEET as the unit. As an example I created a new drawing and connected to a point SDF file.

 

buffer_sdf_coord.jpg

 

The SDF does not have a coordinate system to it and if we check the drawing there is no coordinate system assigned to it yet. Notice I wrote “YET”.

coordinates1.jpg

 

Now let’s create a buffer of 1000 “feet” around a single point. Notice the point and the distance to another point in the map. (646.3171)

 

buffer_create.jpg

 

Here is the results of our buffer, why does it not extend to the other point?

 

buffer_results.jpg

 

Let’s look at the data connection and the buffer’s SDF file to fine out.

 

buffer_sdf_coord.jpg

 

Notice it has a coordinate system assigned to it of Arbitrary XY Meters.

This seems to be the default coordinate system that gets assigned to the SDF file when MAP 3D creates a buffer.

 Now let’s look at the coordinate system of our drawing.

coordinates_afterbuffer.jpg

It now has a coordinate system assigned to it.

While I think it is nice that the developers at AutoDesk programmed this to assign a arbitrary XY coordinate system to the SDF and pass it on to our drawing if it does not have a coordinate system assigned, but why in meters and why not an users option to use feet or any of the other arbitrary XY systems?

So does the buffer tool have a bug or what? I will not say a bug as much as an oversight.

Because if you do have an assigned coordinate system in your drawing to start with the buffer create tool does work as we expect.

buffer_correct.jpg

So if you use your custom template dwt to create new drawings make sure you assign a coordinate system to it until we get a system variable for a default coordinate system.

 

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