Why is the dimension 'negative' in the Dimension dialog'?

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Why is the dimension 'negative' in the Dimension dialog'?

Why is my dimension negative?

Negative Dimensions.

The sign appears if the coordinate of a dimension is negative.

Generally, do not delete the sign, but edit the dimension in the normal way.

More Details

MD-Negative-DimA

Lines have an X-Y coordinate-system.

The 0,0 of a Line is at its start-Point

The +X-axis of a Line is from its start-Point(1) to its end-Point(2)

The +Y-axis of a Line is at +90º from the Line.

When you add a dimension that is a perpendicular-distance from the Line, the:

dimension is Positive when the dimension is in +y-axis half of the Line (blue area in the image).

dimension is Negative when the dimension is in the –y-axis of the Line (green area in the image).

In the top image:

dimensions from the Line(1 to 2) to Points a and b are positive

dimensions from the Line(1 to 2) to Points c and d are negative

MD-Negative-DimB

The X and Y-axes of a Part also have their own coordinate-system! They are similar to Lines.

The bottom image to the left shows the Coordinate-System of the Y-axis

The local +x-axis of the Y-axis of a Part is along the Y-axis!

In the bottom image:

dimensions from the Y-axis to Points a and b are positive.

dimensions from the Y-axis to Points c and d are negative.