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[WP 34S] Ideas for improving unit conversions
02-01-2014, 10:16 PM (This post was last modified: 11-15-2014 11:07 PM by Bit.)
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[WP 34S] Ideas for improving unit conversions

1. U.S. survey foot & co.

Two units based on the U.S. survey foot are called 'feetUS' and 'acreUS' in the WP 34S conversion menu. These names are potentially misleading because they seem to suggest that it's the survey foot based units that are typically used in the United States. However, as explained in http://physics.nist.gov/Pubs/SP811/appenB.html#B.6 and http://en.wikipedia.org/wiki/Foot_%28len...urvey_foot survey foot based units are only used to represent geodetic data (and not even all geodetic data). The U.S. uses the international foot, and units derived from that, in most cases.

Therefore I suggest that 'feetUS' be renamed to 'srv.ft', 'acreUS' to 'srv.ac', and 'acreUK' to plain 'acres'. I've attached a small patch that accomplishes this.

Fathoms should receive the same treatment, i.e. international fathoms should be distinguished from U.S. survey fathoms. The NIST document only mentions fathoms based on the U.S. survey foot (by contrast it explicitly lists the two types of feet and miles), however, there are references to international fathoms elsewhere. The only fathom conversion currently available in the WP 34S is based on the U.S. survey foot, so my patch renames 'fathom' to 'sv.ftm' and adds 'fathom' as a new conversion for international fathoms. Fathoms are rarely used nowadays AFAIK and they are very easy to convert as a fathom of either type is precisely two yards of the same type, so I'm not sure it makes sense to include fathom conversions at all.

2. Cubic foot

Cubic feet are called 'cft' in the WP 34S but to the best of my knowledge this abbreviation is rarely used and in my opinion it may not be immediately obvious what it stands for. I suggest the much more commonly seen 'cu ft' instead.

3. Square foot and miles per gallon

The relatively benign square foot and the truly horrendous miles/gallon appear quite often in the lives of those of us who have to deal with non-metric units. I've attached a patch that adds the (international) square foot and both the U.K. and U.S. miles/gallon conversions (as well as the 'cu ft' name change). They can be enabled or disabled at compile time so they take up no space in the firmware for those who don't want them. The miles/gallon conversions only appear once each in the imperial<->metric form (using double arrows, see the picture) because the same calculation is performed in both directions and the conversion catalog is less cluttered this way. Also the metric part (l/100 km) has to be abbreviated a little too much so in my opinion it looks better if it only shows up on the right side. (This could be easily changed.)

   

4. Order of conversions in the catalog

Currently arrows come after letters in the alphabetical order when sorting catalogs. This results in e.g. 'mmHg->Pa' preceeding 'm->feet' in the conversion menu. I found it rather confusing because it's the opposite of how things are typically sorted. Arrows would usually be considered separators and shorter words (the part before the arrow) would come before longer ones. I've attached a patch that changes this as a compile time option. It has no effect on firmware size and catalog navigation works as before.


Any feedback is welcome.

Edit: Updated patches and compiled binaries are available in Bit's WP 34S and 31S patches and custom binaries.


Attached File(s)
.zip  unit_conversion_patches_20140201.zip (Size: 3.82 KB / Downloads: 4)
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[WP 34S] Ideas for improving unit conversions - Bit - 02-01-2014 10:16 PM



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