English/metric measurement error in the Mars Climate Orbiter

[Hans Pearson]

I have a Rabone tape measure that has 10 inches to the standard foot, the individual inch is also divided into 10 divisions. I cannot find any reference to this measuring system

[hemmjo]

If it is really 10 divisions per actual foot, it is an engineer or surveyors tape.


I was outside on my phone for the first part of this.

The tape you have is not graduated in feet and inches, it in feet, tenths and hundredths of feet.

In the photo of my two survey sticks, you can see which one has had the most use,

4 ft 7 3/8 inch = 4.61 ft (read the top of the red line)

[Hans Pearson]

Thank you for that information. It was actually passed down to me from an engineering-based person who had owned a sheet metal works.

[tonyfoale]

Thank you for that information. It was actually passed down to me from an engineering-based person who had owned a sheet metal works.

It is a big mistake to attempt to see anything reasonable in the imperial system or its offshoots. That comes from someone brought up on the system. My advice is to burn all rulers not graduated in mm.

[mklotz]

It is a big mistake to attempt to see anything reasonable in the imperial system or its offshoots. That comes from someone brought up on the system. My advice is to burn all rulers not graduated in mm.

Good advice, Tony.

One of my favorite examples of the idiocy of the inferial* system is having a volume unit depend on what is contained in said volume...

There are seven different barrel sizes used in the USA, with the size being dependent on the contents. Their names and metric equivalents are as follows: US cranberry (95.5 liters), US dry (115.628 liters), US liquid (119.24 liters), US federal (117.348 liters), US federal proof spirits (151.416 liters), US drum (208.4 liters), US petroleum (135 kg.), US petroleum statistical (158.99 liters)

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* my term for the further botched version of the Imperial system used in the USA under the name "US Customary Units". "Inferial" is a portmanteau of "inferior/infuriating" and "Imperial".

[hemmjo]

I know we are not supposed to talk politics here, but I do think this is bit relevant to the Metric vs Imperial system. Jon, if you wish to delete this, I will not be offended.

We are in this metric vs imperial situation all due to politicians. https://www.thefactsite.com/imperial-metric-facts/

I simply live my life, use what tools I have to do what I need to do. I am comfortable using either system. To me they are simply a different language. I was raised speaking English. I also know a little, very little, Spanish, French and Haitian Creole from some mission work I have done in the past. Neither of those is wrong, just different andI know one A LOT better than the other three.

I can measure in both and have both to measure with. I have a great number of precision measuring tools that belonged to my father. Some from the 1930's. I learned a lot from him and miss him a lot. Someone suggesting that I throw them out, even if I do respect the person, is not going to sit well with me.

Let's all use the system we are comfortable with and not criticize. Nothing we say here is going to change the fact there is more than one measuring system.

[mklotz]

...
I can measure in both and have both to measure with. I have a great number of precision measuring tools that belonged to my father. Some from the 1930's. I learned a lot from him and miss him a lot. Someone suggesting that I throw them out, even if I do respect the person, is not going to sit well with me.

Let's all use the system we are comfortable with and not criticize. Nothing we say here is going to change the fact there is more than one measuring system.

An extract from my broadside on discussing measurement systems...

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An insidious so-called argument to avoid is the exceedingly narrow-minded idea that only the aspect of a measurement system you personally use is a proper basis for deciding which measurement system is best for the society at large. It goes something like this...

I don't need another system to machine my parts. The difference between inferial* and metric is just a factor of 25.4, why bother changing; I can make accurate parts using my present inferial system.

There might be some validity to this approach IF THE JOB OF EVERYONE IN THE SOCIETY INVOLVED NOTHING MORE THAN MAKING LINEAR MEASUREMENTS. People have many jobs involving all the aspects of the measurement system. Using one that's antiquated, un-necessarily complex and confusing leads to inefficiency, lost time and dangerous mistakes.

Another so-called argument I've heard goes something like this: What's so great about metric; there are lots of ways of measuring things. While that's true, if you design your alternate system to incorporate the advantages listed at the beginning of this treatise, you will have a system remarkably similar to the metric system. The standards for length, mass, etc. might be different but, as we've seen, the size of the standards are irrelevant; it's how those standards are subdivided and related that makes the system practical and efficient to use. So why create a system that's very similar to the existing metric system? The existing system is already in use in most of the civilized world and there are real advantages to using an existing system.

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An older copy of the broadside itself can be found here...

A glimmer of hope

I can supply the most current version if requested.

I suppose a succinct warning might be something like...

Don't use any form of transportation that's being maintained in a country that professes to understand and use two different measurement systems.

[Philip Davies]

Of course, an 11 inch ruler would allow them to calculate circumference.

[mklotz]

Just in case you still think it's reasonable to have two or more measurement systems in use at the same time, take a look at these examples...

https://www.conantphysics.com/wp-con...easurement.pdf

Most distressing is this quote...

Note that aircraft altitudes are in feet throughout the world, except for China, Mongolia, and the CIS (former Soviet states), which use meters.

Think about what happens if some already metric nation decides to follow China's lead. How do you guarantee that the notification of the switchover reaches all the people who need to know about it? How do you guarantee these people, once informed, take all the necessary actions in response to the changeover?

I believe most aircraft autopilots currently accept inputs in feet. (Correct me if I'm wrong on that.) Does that mean that, if the pilot is assigned a flight level in meters, he must make a conversion to feet before adjusting the autopilot? Sounds like a recipe for disaster to me.