>>> Pat Naughtin <[EMAIL PROTECTED]> 2001-02-20 22:49:49 >>> Dear Greg and All, I have interspersed some comments. ==gwp================================= Likewise... greg =================================== on 2001-02-20 01.22, Gregory Peterson at [EMAIL PROTECTED] wrote: > Why not square hectometre (hm²)? The symbol is easily explained as "Hundred > Metres on each side" For years the chemists maintained that the decimetre should be taught in schools to support the cubic decimetre in chemistry. In the meantime the chemists were rapidly embracing the simplicity of litres, millilitres, and microlitres. Similarly, your suggestion would require the teaching of hectometres in schools to support the concept of square hectometres. And knowing teachers as I do, they would soon add all of the remaining non-preferred SI prefixes. There's nothing wrong with the use of these prefixes except it slows down the adoption of metric and SI dramatically. ==gwp===================================== I agree with you on this point, when it comes to teaching the general public. Teach them the mm, cm, m, km; cm2, m2, ha, km2, mg, g, kg; mL, L, m3 (and/or kL), kPa, kW, kJ, and °C and that's it. That's all the general knowledge they need to survive in a metric economy. After all the Imperial/wombat folks rarely use more than inch, foot, mile; sq. in., sq. ft, sq. yd., acre, sq. mile; ounce, gallon, bushell, cu. in., cu. ft., cu. yd.; ounce, pound, ton; psi, inHg, BTU, BTU/h, and °F. On the other hand our students should see the complete metric system as it was designed. Much like, in the past, our students should have seen the entire Imperial system as it was designed in order to see the rationale behind the system. When I was in school the "x10" prefixes were given the same emphasis as the "x1000" prefixes. However, once we started applying metric to practical problems only the common metric prefixes were used: mm, cm, m, km; cm2, m2, ha, km2; g, kg, t; cm3, ml, dm3, L, and m3. I was taught that a hectare was a special name for square hectometre, litre was as special name for cubic decimetre, and millilitre was a special name for cubic centimetre. I was also taught the relationship 1 mL = 1 cm3 = 1 g water. I have the advantage over those who were educated in metric as adults that I can use the "non-preferred" units when they are appropriate. I routinely use the dm when I want to calculate large volumes. I routinely use cm to calculate small volumes. I can still estimate using cm better than I can mm. I will still use cm up to about 200, then switch to metres. I also use mm, but only up to about 50 then switch to cm. ======================================= True you can say that a hectometre is 100 m on each side. You could just as easily say that a hectare can be thought of as a square that is 100 m on each side. ==gwp====================================== I was not using the number 100, but the word "hundred" to illustrate that hm could easily mean "H"undred "M"etres. Just like hg could easily mean "H"undred "G"rams. Whatever it takes to make it easier to. ======================================== > In a recent conversation with the fellow responsible for water management in > British Columbia he told me that he was in the process of implementing cubic > decametres (or square "dekameters" if you choose) for large volumes of water. > The are practical uses for uncommon SI units. 1 dam³ is approx. 1.2 acre-feet. This is dangerous ground in terms of conversion to SI. Where there is a seemingly simple 'conversion factor' it is my experience that it takes much longer to complete the conversion. Your statement '1 dam³ is approx. 1.2 acre-feet' would have the effect of preserving the acre-feet unit for some generations of irrigators. ==gwp======================================= The unforatunate situation here is that this fellow is restriced by his supervisor as to how much he can change the price structure for water use. His supervisor asked him to "just convert all this to metric." It was only afterwards that he realized how complicated an effort this would going to be. Since the current price structure is based on Imperial volumes then it would be much more convenient for him to use metric values that approximate Imperial values. The danger they face by adopting 100% rational metric values is that companies who already have water use permits issued in Imperial may complain that the new metric permits allow for an increase in water use, or a decrease in rates. Alternatively the new metric permit holders may complain that they have to pay more or can use less water than the current Imperial permit holders. To you and I this would is merely and inconvenience that will be resolved on its own if left until all the Imperial permits expire and they are required to reapply under the new metric price structure. However to a government who has a lifespan of only a few years this is a major concern, especially in BC there the current New Democratic government (a left wing, social democrat, labour party) is most likely not going to survive the next election. I argued for a 100% rational adjustment of prices to meet the a hard rational metric pricing structure using dm3, m, and dam3 units (or even L, kL, and ML) but this fellow's hands were tied. I must also point out that this isn't strictly for irrigation. It is also used for hydro-electricity, pulp and paper mills, campgrounds, cities and municipalities, mining, etc. A diverse group with diverse water requirements. ========================================= Our experience in Australia is that the adoption of kilolitres and megalitres avoided conversion factors, so it was possible for irrigation farmers to adopt a new SI mind-set. ==gwp======================================= Just as easily as farmers using m3 and dam3 also avoid conversion factors. I could have just as easily said that 1 acre-foot = approx 1.2 ML. ========================================= > BTW... cubic decametres is symbolized by dam³. A rather appropriate symbol for > water management. :) True, this is amusing, and because of that it would possibly encourage some to deliberately select the slowest possible path to SI. ==gwp====================================== That was a bit of a cheap shot, wasn't it, Pat? :( We're all on the same side here. ======================================== > greg > >>>> Gene Mechtly <[EMAIL PROTECTED]> 2001-02-16 20:57:48 >>> > On Fri, 16 Feb 2001, Joseph B. Reid wrote: >> ... I predict a long life for the nautical mile, knot, and hectare. > Your prediction might be realized, Joe, but I advocate meter > squared (m2 as the simplified symbol) for the US, not hectare. > Gene. > Cheers, Pat Naughtin CAMS Geelong, Australia
