Incorrect length unit conversion

[yuyichao]

Hi,

When showing a value with a unit of length (e.g. cloud base or visibility), I very often get numbers that doesn't seem right (like a visibility of 20sm in a rain) and indeed are always much larger than the real value. Looking at the code it seems that the input to Picker.createHTML is likely the correct number in imperial unit though the conversion functions conv.ft.conversion and conv.m.conversion both assume that the input is in metric unit (the one used for cloud base is a for meters and 3.28 * a for feet). This causes the number shown for cloud base to be off by 3.28, which easily makes the difference between VFR and IFR....
I did not check all other units. They could have the same issue but is much harder to verify for me.

This issue could be locale/setting dependent since my browser's locale is zh-CN, which uses metric unit. I also want to say it didn't used to be an issue when I first found this in early January this year but only starts to happen a month or two after that (in case this helps locating the code upgrade that triggers the issue....).