Rounding....what say you?

For the purpose of design mapping, I like to round to the most conservative number.  For example, because flatter pipe slopes are more worrisome, invert elevations get rounded up to show a worst-case scenario.  Similarly, wire heights get rounded down because clearance is the typical issue.

I think I heard something along the lines of "When rounding a 5: If the next leading digit is even, round up. If the next leading digit is odd, round down." I think it's intended to equalize the effect of rounding the 5 digit because it falls exactly halfway between 0 and the next "higher" 0. Always rounding up skews the resulting calculation, supposedly.

@john-putnam Yep.  When I list an acreage just about anywhere I round down so worst case scenario the owner discovers they have more land than they thought they did.

I round to the even number; 24.5 to 24, 23.5 to 24

Several years ago, I had a reviewer reject a plat submittal because one of my lot acreages “was wrong”. The minimum lot size was “1.50 acres”. One of the lots calc’ed at 1.4995, so I rounded up to 1.50 acres.

The reviewer informed me that while numbers can be rounded down, they cannot be rounded up because “you’re adding something to the number that doesn’t exist”. (The reviewer had a handy-dandy cogo program and would run each lot).

Luckily, this lot adjoined a 4+ acre lot, so I “moved” the common lot line 0.01’ to make the acreage work… 😐

Posted by: @surv8r

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The reviewer informed me that while numbers can be rounded down, they cannot be rounded up because “you’re adding something to the number that doesn’t exist”

But you can delete land that actually exists?  What a nonsense argument.  😆 

I learned to round to the even number so there will be no prime numbers to deal with.

Posted by: @peter-lothian

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I think I heard something along the lines of "When rounding a 5: If the next leading digit is even, round up. If the next leading digit is odd, round down." I think it's intended to equalize the effect of rounding the 5 digit because it falls exactly halfway between 0 and the next "higher" 0. Always rounding up skews the resulting calculation, supposedly.

This sounds very familiar. I think you hit the nail on the head.

Good to know I'm not losing my mind...not yet anyway.

Posted by: @peter-lothian

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"When rounding a 5: If the next leading digit is even, round up. If the next leading digit is odd, round down."

The abbreviated version that I learned years ago of this method was "Even-Up"

Another name for Gaussian rounding is Banker's rounding.  There's a setting for it in Autodesk but I never found one for Carlson.  You'd think it would be mandatory learning in college but I only found out about it here.

Posted by: @surv8r

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Luckily, this lot adjoined a 4+ acre lot, so I “moved” the common lot line 0.01’ to make the acreage work… 😐

You could have moved the boundary 0.004' and probably achieved the same thing. The dimension label to the hundreth of a foot would not change but the area would. But battles of wits with the unarmed are rarely fruitful.   

@peter-lothian We call that military rounding.

@squirl 

That is how I was trained as an 82C. We called it "Artillery round-off". 

@cv In the mortar section we round both ways and send an HEQ to each..lol

what does the Q stand for ? 

HEQ ?  High Explosive ?

High EQplosive perhaps? 😉 

High explosive, quick fuse setting..