Unit Conversion Ratios

[Hageta]

I am currently working on this issue that involves unit conversion to LDraw (currently all units are first converted to mm and then to ldu).

And I came up with the following conversion ratios:

[Micron/Micrometer(μm): 400μm * 0.0025ldu/μm = 1ldu]

Millimeter(mm): 0.4m * 2.5ldu/mm = 1ldu

Centimeter(dm): 0.04m * 25ldu/cm = 1ldu

[Decimeter(dm): 0.004m * 250ldu/dm = 1ldu]

Meter(m): 0.0004m * 2500ldu/m = 1ldu

Inch(in, ″): 1/64in * 64ldu/in = 1ldu

Foot(ft, ′): 0.001312336ft * 762ldu/ft ~ 1ldu


Please take a look if I got everthing right.

* everthing in [] is just here for completness, allthough micron is actually a valid unit in 3mf files.

[Hageta]

I am not quite sure if the feet conversion is correct.

[Peter Blomberg]

...(currently all units are first convert to mm and then to ldu).

This is the preferred programmatic practice. Easier to detect errors and to troubleshoot.

Your equations contained a few typos. The conversion factors seem to be mostly ok.
The LDU is defined as 2.5 LDU/mm.

1 mm = 2.5 LDU
1 cm = 10 mm = 25 LDU
1 dm = 100 mm = 250 LDU
1 m = 1000 mm = 2500 LDU
100 µm = 0.1 mm = 0.25 LDU
10 µm = 0.01 mm = 0.025 LDU
1 µm = 0.001 mm = 0.0025 LDU

One international inch is defined as 25.4 mm.
1 in = 25.4 mm = 63.5 LDU

Assuming one foot is twelve inches:
1 ft = 12 in = 304.8 mm = 762 LDU

[Hageta]

This is the preferred programmatic practice. Easier to detect errors and to troubleshoot.

Your equations contained a few typos. The conversion factors seem to be mostly ok.
The LDU is defined as 2.5 LDU/mm.

1 mm = 2.5 LDU
1 cm = 10 mm = 25 LDU
1 dm = 100 mm = 250 LDU
1 m = 1000 mm = 2500 LDU
100 µm = 0.1 mm = 0.25 LDU
10 µm = 0.01 mm = 0.025 LDU
1 µm = 0.001 mm = 0.0025 LDU

One international inch is defined as 25.4 mm.
1 in = 25.4 mm = 63.5 LDU

Assuming one foot is twelve inches:
1 ft = 12 in = 304.8 mm = 762 LDU

The current documentation says 1 LDU is approximated with 1/64 in. I guess using 63.5 as a conversion factor is more accurate.
An explanation of this difference should probably be in the documentation overhaul if it is not already there.