Most (if not all) modeling programs have measurement units of some sort. As they are needed to create the mathematical underpinnings of a mesh. More often than not, the units are arbitrary non-dimensional ones. Thus it is up to the person modeling to decide what the unit represents (whether it's inches, cm, feet, miles, km, cubits, furlongs, etc.) In most cases within the modeling environment, measurements are called "program name"-units. So in Blender it would be Blender-units, in Wings it would be Wings-units. Not that it really matters as 1-unit in one program is usually 1-unit in another program. However the scale which 1 unit represents varys quite a bit between programs. Also some of the higher-end programs support real-world dimensional units. Somewhere in the code they have conversions for metric, english, and maybe a few archaic units of measure. In most cases, there's also a way to set what unit will be represented when the mesh is output. If that's not an option, it usually does a conversion to some metric unit of measure. Just remember when this is exported, that dimensions will be lost - and it will be up to the end user to determine the proper (or at least desired) scaling factor. In most cases when modeling from real world objects, there is a way to place a blueprint behind the modeling space. Then the modeler can just eyeball it so that the model matches the views. (No yardstick required.) Also it is important to use an isometric viewing mode when doing this to prevent errors due to perspective distortion and parallax.

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.