Community Forums

Share:

I'm going to say this right now  

Page 2 / 7

Jim in AZ
Posts: 270
Member
(@jamesf1)
250+ posts
Joined: 9 years ago

Tommy - that would thin out the ranks considerably in my State...

Reply
Norman Oklahoma
Posts: 4679
Member
(@norman-oklahoma)
2,500+ posts
Joined: 5 years ago

Most probably these things happen because the C3d parcel or line label style in use is set that way. It is evidence of poor CAD work, quality control,  & quality assurance, but not an intentional thing.  

Reply
holy cow
Posts: 15725
Member
(@holy-cow)
10,000+ posts
Joined: 9 years ago

Courtesy of one of the great sages of the 20th Century: “Stupid is as stupid does.” – Forrest Gump

Reply
holy cow
Posts: 15725
Member
(@holy-cow)
10,000+ posts
Joined: 9 years ago

A few years ago I was asked to review a preliminary plat being prepared for a nearby city.  The first red flag was noticing that every bearing had arc-seconds to five decimal places, e.g. 47.12345"  This was on block lines in a small subdivision.  As I recall I figured a line would have to be roughly 50 miles long before the difference between 47.12345 and 47.12346 would be a quarter of an inch.  Forget curvature of the Earth and all sorts of other things.  BTW, the plat was provided to me by the city, so obviously the surveyor didn't see anything wrong with such crap.

Reply
jt1950
Posts: 100
Member
(@jt50)
100+ posts
Joined: 6 months ago

Not sure what the problem is with over precision of units? So what if he computed out to 10 decimal places? You just round it off to whatever decimal places your instrument is capable of laying out right? Problem solved, you get paid, on to the next client/

Reply
3 Replies
Tommy Young
Member
(@tommy-young)
Joined: 9 years ago

1,000+ posts
Posts: 2304

@jt50

You do realize that we can't, or don't, measure accurately enough to calculate areas like that, right?

Reply
dmyhill
Member
(@dmyhill)
Joined: 9 years ago

1,000+ posts
Posts: 1356

@jt50

The "science" of surveying involves acknowledgement of significant digits. 

A few points on that:

  • Using significant digits may not increase your precision, but it will improve the accuracy of your statements. (If you can reproduce a measurement of 1 foot 100% of the time, then stating "1 foot" is more accurate than stating "1.0001 foot" when your measurements vary by 0.1' every time. It is about the accuracy of your statements.
  • Measurements are subject to significant digits.
  • Calculations (still subject to significant digits) can typically be of greater precision than your ability to measure. In the time of slide rules, then the precision of your measurement tools informed how precise you cared to make your calculations. So simply saying that you cannot measure better than 0.01' does not mean that some calculations could not reflect a better precision without violating the principles. 

   We spent about a week in High School learning about and practicing significant digits during my Chemistry class. I think that would be a great refresher course for a surveyor's conference. 

In practice we see how well measurements can be reproduced on the ground every day when we do our field work.

 
For instance, if I hit a corner by another surveyor within a tenth of a foot I am generally pretty satisfied. I wouldn't generally even consider that tenth as missing the corner. So let's apply that to a 100'x100' box (10,000 sqft)... 
If I am off by a tenth all the way around in the wrong direction I could have between 9960 and 10040 sqft inside of the corners. So, I would submit that most of us violate significant digits almost every single day.  

Reply
BStrand
Member
(@bstrand)
Joined: 2 years ago

250+ posts
Posts: 303
Posted by: @jt50

Not sure what the problem is with over precision of units? So what if he computed out to 10 decimal places? You just round it off to whatever decimal places your instrument is capable of laying out right? Problem solved, you get paid, on to the next client/

Well, the person drafting the plat is probably working off a boundary/topo survey performed with equipment of lesser precision than what he's calculating for his lot dimensions, so right off the bat he's introducing error.  If you ignore it you either look equally ignorant or careless.

Reply
Page 2 / 7
Default
:)
:d
:wink:
:mrgreen:
:neutral:
:twisted:
:arrow:
:shock:
:???:
:cool:
:evil:
:oops:
:razz:
:roll:
:cry:
:eek:
:lol:
:mad:
:sad:
:!:
:?:
:idea:
:hmm:
:beg:
:whew:
:chuckle:
:silly:
:envy:
:shutmouth: