AutoCAD Civil 3D General Discussion

Reply
Distinguished Contributor
AussieHans
Posts: 766
Registered: ‎06-26-2006
Message 11 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-26-2009 01:59 PM in reply to: jwilkerson
We are a surveying firm and we deliver the completed DTM to the Engineer, either as a Civil3D surface, or as 3D faces. We don't let the Engineers create the DTM from hour data, we consider this very risky practice. Surveyors that create the DTM soon realize the shortcomings of their surveys, and learn to be thorough. Also, surely the bloke who has been in the field needs to create the DTM, he knows what's there, what the ground really looks like?
*Laurie
Message 12 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-26-2009 02:12 PM in reply to: jwilkerson
Hi jwilkerson,

If you care to look at an elegant third party solution to this isue then
http://www.stringersurvey.com/ has it.

Regards,


Laurie Comerford


jwilkerson wrote:
> I am a civil engineer (as well as the CAD guro at my company) and I have
> been having issues with our surveyors not get enough shots in the field.
> Specifically, when they shoot the top X and bottom X of ramp and
> driveway curb transitions, they only shoot the TC elevation and not the
> adjacent flowline and edge of gutter. This causes problems with crossing
> breaklines (especially around curves) when we go to build the DTM. I
> understand that these elevations can be found by interpolation but that
> requires a lot of post processing. I am just curious what the industry
> standard is on this issue. Thanks, Jeff
Distinguished Mentor
andrewpuller3811
Posts: 765
Registered: ‎07-30-2008
Message 13 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-26-2009 02:27 PM in reply to: jwilkerson
Having been a Graduate surveyor for 8 years and now a engineering designer for 2, I know how much difference a good dtm makes. It's a pity some bosses don't.

Some days you get in trouble for taking 10 too many shots. Then other days you get in trouble because you don't get enough.

Give the surveyor a detailed brief as already stated, that way the survey manager/boss has to make sure a good number of shots are measured. It's also extremely helpful to the field party to have a detailed brief from the client. Most companies have a set way of doing a topo survey, so letting them know exactly what you want can solve any problems before they occur. My previous employer only got top of kerb back for most topo's. If you have given them a brief then they have no come back if you say where are the gutter shots etc.

A lot of companies over here have dedicated drafters, and they send the survey crews out all day to do surveys, then the drafters will draw it up the next day. Yes reducing your own survey is best because having been on the ground, you know the lay of the land, but that is not always the way things work out.
If this fixed your issue, click on "Accept as Solution"

Andrew Puller
Maitland, NSW, Australia
Windows 7 Enterprise 64bit
Intel core i7 2600 @ 3.40 GHz with 16GB Ram
Civil 3d 2013 64bit
Distinguished Contributor
omc-usnr
Posts: 621
Registered: ‎04-25-2007
Message 14 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-26-2009 03:38 PM in reply to: jwilkerson
No 3rd party softwware, no matter how elegant, is going to make up for missing data. Field crews must be trained or informed as to what is needed to ACCURATELY represent a surface. I've worked both sides of this, and I'll have to agree, the best solution is to have the guy who had the rod in his hands draw the map. This really isn't going too happen often, so the people in the field need to know what the people in the office need to produce an accurate topo. In a section, any hard edge needs a shot, and it needs to be in line, not staggered. In the old days when points were a solid block, this was a pain, but now there's just no excuse.

As far as I can tell, there's really no excuse for not taking the shot. It's always cheaper to have too much data than not enough.

I now do more office design work, and work with several different surveyors, and most of the guys do a pretty good job. I'm pretty clear right up front what I need, which will always include going beyond the property line / fence line by 20' so the surface has somethign to chew on at the edges. If your in-house guys aren't getting the job done, you maybe need to let some of them go and find some that will.

Reid
*neilw
Message 15 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-26-2009 03:58 PM in reply to: jwilkerson

I think there can be a balance in determining what
is necessary to shoot in the field. It would not be necessary to shoot every
breakline if it can be interpolated adequately in the office. An edge of
pavement and back of curb should be adequate to model a curb by interpolation
and could save unnecessary measurements in the field. Ilso, if the
surveyors are responsible for providing the DTM from field measurements they
will quickly learn what shots they need to take. Really they should be trained
to develop the DTM's for existing conditions since they best know the
site and the data.

 



style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">I
am a civil engineer (as well as the CAD guro at my company) and I have been
having issues with our surveyors not get enough shots in the field.
Specifically, when they shoot the top X and bottom X of ramp and driveway curb
transitions, they only shoot the TC elevation and not the adjacent flowline
and edge of gutter. This causes problems with crossing breaklines (especially
around curves) when we go to build the DTM. I understand that these elevations
can be found by interpolation but that requires a lot of post processing. I am
just curious what the industry standard is on this issue. Thanks,
Jeff
*Laurie
Message 16 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-26-2009 08:28 PM in reply to: jwilkerson
Hi Reid,

Of course software can't make up for missing data (except in the minds
of CEOs/managers/accountants/architects/contour centric drafters/etc.),
but it can be used to automatically interpret constant section data such
as uniform kerb sections based on a single point pickup, something the
Autodesk system can't do. With the fieldbook process you must either
increase the field pickup or hand offset breakline information.

On the issue of building the DTM, only the field surveyor should build
the model. No-one else is in a position to judge if the model is a
reasonable representation of the existing conditions.

If this means managerial changes then they should happen.

As AussieHans indicated, briefing for survey work in Australia almost
invariably requires the DTM as part of the survey deliverables.

Also many organisations require that an additional set of randomly
located survey points are taken and the difference between their
elevations and the elevations predicted by the surface model must be
below a nominated tolerance as a measure of quality of the surface.


Regards,


Laurie Comerford
omc-usnr wrote:
> No 3rd party softwware, no matter how elegant, is going to make up for
> missing data. Field crews must be trained or informed as to what is
> needed to ACCURATELY represent a surface. I've worked both sides of
> this, and I'll have to agree, the best solution is to have the guy who
> had the rod in his hands draw the map. This really isn't going too
> happen often, so the people in the field need to know what the people in
> the office need to produce an accurate topo. In a section, any hard edge
> needs a shot, and it needs to be in line, not staggered. In the old days
> when points were a solid block, this was a pain, but now there's just no
> excuse. As far as I can tell, there's really no excuse for not taking
> the shot. It's always cheaper to have too much data than not enough. I
> now do more office design work, and work with several different
> surveyors, and most of the guys do a pretty good job. I'm pretty clear
> right up front what I need, which will always include going beyond the
> property line / fence line by 20' so the surface has somethign to chew
> on at the edges. If your in-house guys aren't getting the job done, you
> maybe need to let some of them go and find some that will. Reid
Distinguished Contributor
mdriver1
Posts: 337
Registered: ‎01-24-2008
Message 17 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-27-2009 05:27 AM in reply to: jwilkerson
First Jeff called upon surveyors to express their opinions. Not to take any good advice from the good folks on ths group but who, of the posts to date, are licensed, veterened or just surveyors on a crew? I see comments like "I worked for a surveyor as a CAD manager", etc. Just curious. Not attacking anyone here.

Now Laurie mentioned that program that he always pushes. Nothing wrong with advertising but didn't Jeff specifically want to speak in terms of not interpolating the data and why can't the surveyor just take the shot?
He's right. In order to model the existing field conditions one must take a data point where needed and in my opinion top back curb, top face curb and flowline shots are needed due to the vertical variation and not so much horizontal. I mean would you just shoot the top of a 1 foot tall 3:1 slope and interpolate the toe? I think not and the 1 foot tall 3:1 slope is merely an example.

Now there are some very good points given but I have a comment on the surveyor being the one and only one to create DTM's. True that it's best to allow the person who walked the terrain but that's not always possible. A properly trained CAD person, civil engineer, etc. that knows how to actually read a contour map could mark it up via a field walk and get with the survey crew for clarification. Communication's the key here. I was actually suprised that the engineering school I graduated from did not have any required classes whatsoever regarding the generation of topographical or grading maps. Sure survey classes were offered, AutoCAD as an elective was offered, etc. but no real here's how you grade a roadway using the design horizontal and vertical alignments. You know finding where your even elevations (such as 2's and 10's) cross the design profile, at what station and plotting that on the plan view, etc. Finding the distance needed along that horizontal alignment to drop the 2% cross slope at 12.5' at a certain centerline grade? Remember doing that? Anyone, Anyone, Bueller? Not to say that this will not happen in the future but doubt it. I mean isn't that what a civil engineer does a lot of but has some nifty program to do it for him/her? I guess my experience got a little in the way during school.

I sometimes get some grief when I show up on the job by myself but when I produce the topography map or once they work with me the view becomes very different. Again nothing replaces the person who walked it and totally agree but a well trained associate can generate and spot errors in the model for sure. I like the cross-training comment.

Oh, the comment that some surveyors are just not CAD literate. Very true but do you really need to understand a CAD program to think in 3D? I think that's a bad excuse for the untrained field crew. I learned what was needed before learning a modeling program but new some CAD as we mainly were board drafters. Yes I used to draft on the board. Scaled and plotted each X,Y,Z point on gridded mylar and created topographical, field maps, plats etc. Didn't need CAD for that routine just a coordinate sheet, calculator, scale, 2d lead, a ink pen, red and charcoal colored pencils for contours. We had a HP plotter with the pen carousel but it seemed to be down a lot.

Anyway yes I am, as others are here as well 'm sure, a CAD guru (going on almost 20 yrs. worth). In this day and age you have to be a CAD guru or you don't have work but the principles of contouring never change just how it's generated.

Hope my post didn't offend anyone as it wasn't meant to do so. Just a across the board opinion.
Time to get to work.
Mark Driver
*Expert Elite*
Sinc
Posts: 6,207
Registered: ‎11-18-2006
Message 18 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-27-2009 05:54 AM in reply to: jwilkerson
> {quote:title=mdriver1 wrote:}{quote}
> He's right. In order to model the existing field conditions one must take a data point where needed and in my opinion top back curb, top face curb and flowline shots are needed due to the vertical variation and not so much horizontal. I mean would you just shoot the top of a 1 foot tall 3:1 slope and interpolate the toe? I think not and the 1 foot tall 3:1 slope is merely an example.

There is no one answer to all this, which may be part of the problem. As a Surveyor, one of the things we should keep in mind is the purpose of our survey. Is it really necessary to shoot three shots at every curb point? Does it really matter that you pick up the fact that the curb is varying from 5-1/4" high to 6-1/2" high, instead of sitting right at 6"? Sometimes yes, sometimes no.

If the entire purpose of your survey is to fix some drainage issue, then you may need an excessive number of shots - overkill is better in this case. If you are doing a normal topo survey with 1' or 2' contours, then it is overkill, and the field surveyor can probably just shoot one line (either TBC or FL), making sure to hit curb cuts, and the other lines can be created by creating a stepped offset in the office. There are other factors, too - more shots may be needed in flatter areas than in areas with distinct crossfall, etc. And so on.

That's the confusion, I think. There are few really hard rules, and a lot of it is based on common sense and experience.

-- Sinc
http://www.ejsurveying.com
http://www.quuxsoft.com
Sinc
Distinguished Contributor
mdriver1
Posts: 337
Registered: ‎01-24-2008
Message 19 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-27-2009 11:51 AM in reply to: jwilkerson
Good point but I'm not confused and do understand there are more ways to look at it but I do it the way I described. As mentioned my model and it matters to me and it may not matter to the surveyors who Jeff speaks of but he obviously thinks it matters or why complain? I think it's still lazy.

Glad to see a fellow surveyor make a comment though.
Mark Driver
*Christof Lambrecht
Message 20 of 21 (255 Views)

Re: Calling all surveyors, I need your opinion on something.

03-28-2009 01:38 AM in reply to: jwilkerson

I'm in for the communication &
training!

when you have crews that have no cad skills
... you have to design your workflow in such a manner that they have to revise
their own work on the paper plan.  Make sure you have all measured
points & contours on.  Let them take photograps or make a
little movie on the terrain.  Take 10 miniutes and revise this plan
togheter with photo's and movie.  You'll learn both in a fast way. 
You'll be able to make a far better job description for them, they will see
where they have too little or to many points shot, and both will learn
from each others problems.

If you get no better results after some jobs
then sometingin else must be wrong I think ...

 

chr.


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
Good
point but I'm not confused and do understand there are more ways to look at it
but I do it the way I described. As mentioned my model and it matters to me
and it may not matter to the surveyors who Jeff speaks of but he obviously
thinks it matters or why complain? I think it's still lazy. Glad to see a
fellow surveyor make a comment though. Mark Driver

You are not logged in.

Log into access your profile, ask and answer questions, share ideas and more. Haven't signed up yet? Register

Announcements
Are you familiar with the Autodesk Expert Elites? The Expert Elite program is made up of customers that help other customers by sharing knowledge and exemplifying an engaging style of collaboration. To learn more, please visit our Expert Elite website.

Need installation help?

Start with some of our most frequented solutions to get help installing your software.

Ask the Community


Civil 3D Exchange Apps

Created by the community for the community, Autodesk Exchange Apps for AutoCAD Civil 3D helps you achieve greater speed, accuracy, and automation from concept to manufacturing.

Connect with Civil 3D

Twitter

Facebook

Blogs