We have an RFP for some roadwork with the specification of 0.02' horizontal and 0.05' vertical for all topo on a couple miles of road.
Does anybody truly think this is feasible?
For enough $$$$, anything can be done.
But this does seem to be overkill.
> We have an RFP for some roadwork with the specification of 0.02' horizontal and 0.05' vertical for all topo on a couple miles of road.
>
> Does anybody truly think this is feasible?
How are they gonna know how tight your shots are?
0.01
Tech specs on a recent utility project...
"All surveys conducted for the purpose of supplying record drawings shall be recorded in both the latitude/longitude coordinate system, within an accuracy of 0.001 seconds, and the State Plan Florida East NAD 83 Coordinate System, within an accuracy of 0.01 feet. No conversion shall be allowed."
You can run levels/checks all day long between plan benchmarks/control and find nothing tighter than .05'.
Foolishness...
Ask them to hold up two fingers and show you what 0.02' looks like. 😉
or
Call them up and ask, "so you need all the shots within an inch or two?" and they will says, "yes, that sounds good."
They already have two proposals submitted.
I wonder if my explanation of the difficulty of achieving such perfection will change their consideration of the other two...
Prove me wrong.
It's doable...1/4" (0.02') is standard accuracy required for laying out column lines for buildings. Sometimes less.
Use good field practices and the right instrument and you should find your elevations to be within that 0.05' range. At least relative to your primary control. Or use a digital level.
Tom
I know for sure some folks around here that have done city jobs on street work, can't figure out why their closures don't work...just blame it on the surveys before them. I had to leave because these button pushing zoners were leaving my liscense in jeopardy. I actually let my tag go because the affirmative action folks, in my case an India indian, just wanted a yes person. I had told him that we could not send the field data to India to be processed, you know FTF, and then produce the product...I know there are many folks out there that have been in my position, but how many said NO!!
Like others have said...prove me wrong.
But those specs are just dumb
> But those specs are just dumb
The specs are certainly dumb, but no less dumb than anyone who would certify that they've achieved that level of accuracy without applying the equipment, methods and personnel necessary to achieve them. Any licensee who would shrug off the specs and certify anyway is guilty of negligence or incompetence. The proper approach is to educate the client so that he can reissue the RFP using specifications appropriate to the project.
If the RFP stated that all control will meet First Order Class I accuracy requirements, would you say to yourself, "I'll do Third Order work and certify that it's First Order", or would you explain to the client that the cost of meeting those standards would far outweigh the benefit, and advise him on a more appropriate specification?
Yeah, it's doable. Depending by what you mean by topo'ing the road. Around here, contractors are only allowed -.02 depth wise before they start to get dinged for the shortage. + is good, but on their own dime after +.03. Who else is going to check them that close? Engineers?
Run digital levels and keep your shots less than 500'.
Now if you're talking about ground shots, I'd have to agree.
Yes, the ground shots on country paved roads plus 25' off the layout. There's more than 0.02' hz in the aggregate.
There are a few dozen belgium block aprons. If level, the belgium block will have more than 0.05' vt.
Control, I would spec at 0.02 and 0.02 relative with an addition vt error based on datum. (nearest NGS BM >10 miles, I'm sure there is a MassDOT BM within the project).
We also need to structure the contract. In MA we can trespass for a private firm, not a municipality. We should be working for the engineer, not the Town to ensure access to that 25' zone.
Oh well, I cannot wait to see what response I get from undermining the confidence expressed in the other two proposals.
0.02/0.02
We use to do it all the time on runways and it's checked with a computerized profile measuring golf cart.
This was layout not topo,
