If you have the luxury of designing the software, you should be careful about using floating point numbers - they can create all sorts of problems.
A number of years ago I had to design a system that accepted logs of electrical data that was taken at various points around Italy. The data was collected at quarter-hour intervals, 24x7. The time system that I devised was to number the quarter hour starting 00:00 UTC on 1 Jan 2000 as interval 1, the quarter hour starting at 00:15 UTC on 1 Jan 2000 as interval 2 etc. All input data was converted to this format. A database table kept track of when the clocks went forward and when they went back, thus most days had 96 intervals, but one day a year had 100 intervals and another had 92 intervals. Thus time was not strictly SI. BTW, towards the end of last century, I worked on four different Y2K project - three serous project and a non-serious project at http://www.windhorst.org/calendar/. Maybe this will help you. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Pierre Abbat Sent: 19 May 2015 16:32 To: U.S. Metric Association Subject: [USMA:54710] software that uses measurements Other than astronomic (stars' masses are known more precisely in sun's masses than in kilograms), atomic (charges are integral numbers of elementary charges but unround numbers of coulombs), and angular (angles are often expressed as turns divided by an integer rather than radians), are there kinds of data that should be stored in non-metric units? Suppose you're writing a software program that handles measurements, and the data have been expressed in both metric and non-metric units. How do you handle input, storage, and output of data? I'm writing a surveying CAD program called Bezitopo. All data are stored in floating-point coherent SI units, except angles, which are stored in fixed-point 2^-31 turns, unless they're defining a position on the earth, in which case they will probably be stored as floating-point radians. Lengths can be input or output in meters, international feet, US survey feet, or Indian survey feet, but they are always stored in meters. LandXML has a tag that says what units measurements will be stored in. They can all be meters, or they can all be (US or international) feet. Pierre -- La sal en el mar es más que en la sangre. Le sel dans la mer est plus que dans le sang.
