There’s been a hot spot of discussion today regarding the use of hand drawn contours to fix an unsightly surface. Since the original post in the NG is being ignored, I think it’s worthwhile to open the discussion here. Read on and join in the debate.
The point of contention is that in an existing ground surface, adding a polyline at elevation to smooth a contour is a sin. The inquisition claims that this isn’t fixing the surface, but is destroying the integrity of the data. They think the user should be fired.
Isn’t adding a breakline (or contour) fixing the surface? If I’ve been to the site, and I want to make the surface more palatable to the reviewing agency, why is adding a breakline (or contour) such a cardinal sin?
I think the hard-nosed crowd is missing the forest for the trees on this one. Yes, I agree that the data should drive, but I also operate in a real world where sending out a $1000 a day crew to add few points versus adding a breakline to make the contours look “right” to the reviewer is an easy decision.
We’re talking dirt. I spent a day shooting a site with level and rod, calling off 76.64, 76.58, 76.55, etc. (It was Amarillo, TX.) At the end, the chief hands me field book to enter at the office.
76.6 and a line drawn half way down the page. Then 76.4 and a line for a few shots, then 76.5 and a line.
I looked at him, kind of stunned. I worked hard on all those readings! His comment? “It’s just dirt college kid.”
Would you say that was wrong? Would you say that collecting decimal places on dirt is wrong? Then why is adding a breakline (or contour) wrong? Time to step back and remember, “It’s just dirt.”
Fire back in the comments!
I don’t see a huge issue with adding a contour line to adjust a surface slightly, but my concept of a breakline is much different than a contour, and having good breaklines should ultimately provide you with good contours. There is also the question of the type of job you are doing, more accurate for road design, less important for drainage comps, which I’m learning is a lot of throwing darts at c-values anyway it seems 🙂
Matt Moore
O.K. In reality I think both opinions are right depending on the circumstances. But first a point.
When I was first learning Surveying & Engineering (Construction & Boundary) my boss was very particular about reading and setting everything right down to the hundredth. After working for him and learning from him for a while. I got to the point, while setting a particularly difficult, offset that I questioned the need for that level of accuracy when I knew the masons weren’t going to set the forms that accurately. His answer was that if we figure a half a tenth was good enough and the masons figure that a half an inch is good enough then the carpenters figure a quarter inch here and there didn’t matter. Thing could get pretty bad by the time the house was done. I realize now that he also maintained those standards because he cared about training me and others working for him.
Now. Adding a polyline to smooth out a surface. I’ve done it in LDT. Haven’t needed to do it in C3D yet. But the day may come. But I find doing it the “right” way is much easier in C3D.
The question should everyone do it. I don’t think so. I’m a quarter century in to this business. I’ve manually interpolated contours on parcels more times than I like to think. I’ve hand graded both residential and commercial sites. So if after considering the situation I think I need to throw in a hand draw contour. I’m basing it on some experience and more than just a need to have a line look good. So far in C3D I’ve been able to make things look good using the available editing tools. I have a style that shows me the triangles, points and contours at the same time. So I can immediately see the results of the edits on the contours.
I don’t think that adding polylines to correct a surface is a great idea. I will do a lot of work before resorting to that. As far as breaklines go. We create all our breaklines from field shots. If there isn’t a breakline where I think there should be one. I send the crew out to get more information. So if someone with enough experience and a good understanding of surfaces and how they are used wants to add a line or two. That’s O.K. But it’s not a practice I would encourage in people I train.
Is it “Just Dirt”? Up to a point. You can say pennies are “Just Pennies”. Take a Penny – Leave a Penny what does it matter. It doesn’t until your talking truckloads of pennies. The company I work part-time for just got paid good money for me to re-grade a site where it was realized that a LOT of fill would have to be trucked out if the original grading was followed. If you need fill that’s not bad. But there was no place close to get rid of it. Honestly, this was cause by the design grades. Not any mistake in the existing terrain.
To sum up. You can take little shortcuts, you can make some assumptions, and you can consider something “Close enough for Government Work”. But you need the background to understand where the line is. And not to cross it.
A little cheating has to be done everyday.
If you really know what you are doing you’ll never get caught.
If you do get caught dirt is still cheap.
I think a little surface massaging is good. However, in some localities (used to be in St. Charles, MO), it is “illegal” to do so. In the eyes of the court, and again, not mine – if the shot was not taken in the field, the shot cannot exist electronically. Therefore if the contours appear jagged and they need to be smooth, send crews out to obtain more data.
This argument can go both ways; I personally think the land should roll along nicely, just be aware of regulations in your region.
From my experience from working with a construction company I would say it does matter. As part of my job I would go out and survey the site before construction began and check the topo. The comparison surface was usually pretty uniform in difference +/-0.5′ difference either way. If you where to adjust the contours you would end up with areas that where off greater than the average. That was the whole reason I was going out in the field to check the survey because we didn’t trust the contours based on past project experience. As to the original OP, he should have added the pad breaklines to his surface.
My thought on this is if you can’t “trust” the topo gotten from a PLS than why are we paying them so much to go survey the property? I have had to tweak a survey or two in my tenure as a Designer, I admit to it everytime I was asked. I gave a logical reason and was never second guessed.
People do seem to not see the forest when it comes to the rule that what is collected and gotten from a surveyor is ALWAYS 100% accurate. Well it depends on which PLS you talk to. No two PLS’s will agree on the same data. Survey information is derived mostly from personal preference on what should be shot and to what degree of accuracy it should be shot. If I see something didgy in my EG surface … say there should be a slope break where a ditch side slope starts and the surveyed TIN doesn’t show it, you can bet your butt I’ll be adding it.
Being a Designer/Technician means that you have the skills and knowledge to questions something if you don’t think it is right.
In this instance I think we have a case of someone trying to fix something that they thought was not 100% correct.
To explain my statements more, since I am the one signing and the one that is paying the e & o insurance, I do not want anyone adjusting contours without my approval. Also why do they need to be adjusted anyway? A competent field crew should have obtained all necessary points. If it is the field crews fault then it is not the office techs problem. A favorite saying of mine: fix the problem, not the symptom of the problem.
Some background info:
I have had to spend way to many weekends, nights and evenings fixing another employees mistakes that thought they knew what they were doing. Frequently these errors were discovered months after the employee job hopped to one or two more jobs. In one case in 18 months I discovered $125,000 in errors the this employee had cost the company over multiple projects. I was hired to replace and clean up after this person.
Have a deadline, gotta run…
Gary E.
There are too many variables to come up with a CAD answer to this question.
-How flat is the site?
-What is the purpose of the survey (earthwork? new developement? runway approach?)
-What is the existing site covering?
The real answer has less to do with surface modeling software techniques and everything to do with professional judgement and experience. Pretend we don’t have CAD to create contours. How are contours created? By hand calcs, hand drawings, and professional judgement.
CAD is not a black box tool to be handed over to just anyone and allowed to tell us the right answer. Its the user’s duty and responsibilty to guarantee the results. If, in their professional judgement, a contour needs to be adjusted, then it should be adjusted. If a user isn’t able to make that type of judgement call, then they should consult with someone in their office who can.
I’m going to throw my $0.02 in here from a survey perspective.
James is right, it’s just dirt. So many sites now are being built from aerial topos that it’s not even funny. It’s cheaper than a survey crew and *mostly* “good enough” – the stated accuracy is held to within plus or minus half of the contour interval. That’s the whole contour interval if you can do math in your head. I’ve seen subdivisions that have been completely designed from this data and are still standing. I’ve also seen contractors want to know why this pipe sticks up out of the ground when layed by the plans…it can go both ways.
It’s a judgement call. As I told James, I don’t want some fresh grad tweaking my “squiggly lines” because he/she can’t read a topo. However, if someone like Allen up there saw something that they knew was wrong, I’d have to agree with the judgement.
I’m not disagreeing with Gary, but if his workers could be fired for tweaking a contour, then they should be fired for adding a breakline. Why? They’re editing the surface, aren’t they? They’re changing the triangulation of the TIN. If we left our survey crews responsible for collecting enough data that the TIN could just be created from points, then we’d likely call it LIDAR and complain because the program couldn’t handle it. There has to be a mix of work between the field and the office to create an accurate model without spending all of the client’s money.
If you have been there and seen the site then adding data to the surface to fill in the missing information is fine, but using the same techniques to change the data created by somebody else is dangerous and unethical in my book. I can recall several examples where what seems to be a spike in the survey turned out to be a chunk of bedrock sticking out of an otherwise flat piece of ground. I have also seen people delete points along retaining walls because they wanted smooth contours and didn’t bother to check the original data.
It’s not always “just dirt”.
Currently my firm is subbing out all survey work, so I will not edit any of that field data at all. However at previous places of employ we had our own crews and survey techs where many of the survey techs went from field to desk with out proper training in the software, so many “corrections” were necessary. With that in mind what’s a few cubic yards between friends anyway?
Ditto what Scacco said. Professional judgment prevails. Sounds to me as if the issue isn’t about adding a polyline, or CAD at all, but whether or not the decision to edit the surface was a reasonable one. Misplaced blame…poor software!
To add to Jasons comment: Once again it is the survey crew who is responsible for determining the breakline location and obtaining enough points to define it, they are on site, not the cad tech. I view every site we work on so that I know what the contours should look like. Once again I am the one signing it. Having personally viewed the sight and not just from the road but walked the whole thing, woods, briars and all, only then am I in a position to say what the surface looks like.
In the past have had cad techs move a contour so they could add text in that position and other such nonsense as that, I will repeat, having learned the expensive way, moving a contour is a firing offense.
Gary E.
Measure it with a micrometer
Mark it with chalk
Cut it with an axe.
“In the past have had cad techs move a contour so they could add text in that position and other such nonsense as that, I will repeat, having learned the expensive way, moving a contour is a firing offense.”
But Gary, noone is suggesting that it is ok to actually pick up and move a contour – so I don’t see how that is relevant to the discussion. There is a world of difference between what you described and what James described in the original post, which was “adding a polyline at elevation to smooth a contour.”
At the end of the day stuff gets built off those surveys. I live in New Orleans at the end of the day it really DOES matter. Trust me my house is .3 away from paying $800yr in flood insurance vs $1800.
Julie
Feel free to disagree. My understanding was we were talking about moving contours. I am hardnosed because it is cheaper that way.
I suggest taking Wesley Crawfords seminar on construction liability and then get back with me.
I am in no way connected with Professor Crawford, Creative Construction or Purdue University, just took the seminar 2 years ago when he was in town and now it is required for all employees, field or office, that generate plans. Can’t wait until he is back in town so I can take a refresher, I consider it cheap insurance.
http://www.creativeconstruction.com/
Why is everything Black and White? I think the grey area is the important factor, and anyone working on reducing topo should visit the site. Otherwise your a landscape artist trying to paint a picture of mountains while sitting in a cubicle (Might look good but nothing like the real thing).
-Scott Salas
Excellent points to all. Many of you know I am with a small firm that typically does the property & topographic surveys, site/subdivision plans, construction stakeout & as-builts for almost all of our jobs.
Scope of job and modeling technique are the two that points that I had running through my brain but there is also the map maker who just won’t settle for jagged or non-curved proposed contours. We have had both in our firm. One would send the work back until the contours were fluid processions of filleted lines & curves. The other couldn’t give two hoots. Personally I just don’t want contours to look like lightning rods.
The distinction between EG & FG must be made. There is no shot from an FG so this boils down to technique. If a user can is productive designing with contours where appropriate. It’s is fine. We would not expect to see someone modeling a roadway with this method but a pool plot plan, yeah 2 plines for the pool, a daylight & maybe a contour or two. That is only if sections are needed for soil movement. If soil movement permits are not required. We draw the pool and a contour. We make a killing.
We let the points & breaks dictate EG modeling. If after that is said and done and contour error is recognized by the surveyor (he does or checks the EG modeling because he seals it) he uses his best judgment to fix it. The fix may be a hand drawn contour. It may have been a border it may have been a point. In EG professional judgment is a factor. We have had regulations come up with this once as Scott has mentioned but we knew the guidelines for the work & followed them. Professional judgment required.
Shifting a contour a few feet to curve it could be a bucket load on one job, ten trucks on a one day job or 10 trucks on a 100 day job. Dirt may be cheap but fuel is fast becoming a priority variable with divers/contractors.
The saying that contours are a result of a tin holds much more weight with us modeling EG than FG.
How could I bee so rude?
James, excellent topic to bring to the discussion table!
You’re only accurate at a surveyed point, while other points along a rounded ground surface will never be accurately modeled by a strictly surveyed TIN surface. You won’t even get close without your crew chief blowing his top over the shot count. The farther apart the shots are, the worse the model will be.
Creating contours to add to the surface doesn’t mean FAKING the surface. It could be professional judgement, but there’s a better way. If the field crew has shot points at the start, end, and in the middle area of the curve – then you build a TIN – and then make your contours by fitting a curve to the intersection of contours & TIN lines and add your contours to the surface, you KNOW that you end up with a more accurate model than from the points alone.
The trick is to get the survey crew to hit the points that document the curves, so that you have backup for the adjustments made to the initial TIN. This sometimes falls into the “It’s just dirt” category – but sometimes it’s curb & gutter geometry and you NEED the truer model that the curved contours will provide.
Important topic… valuable insights. Jon Rizzo’s reply made me laugh out loud and is sooo true.
However, the OP wanted to grip edit the contours AROUND a building pad (somehow) since he/she couldn’t get a “hide, non-destructive” breakline to work. He/she never mentioned if said surface was EG or FG. The firing was mentioned as being the result of a 2nd offence after training was giving on the software’s solution to the building pad situation. Mr. Peter Funk mentioned how to derive a specific contours information for trimming and re-insertion as a breakline.
The OP went on to confess of “lost hundreds of hours playing with the stupid surface just to show the contours correctly”. I can’t believe he/she told that on themselves and truly exhibits a larger lack of understanding of the tools in the software. Danger, Will Robinson, danger!!!
Again, great topic… it IS just dirt… but it’s also just our job! It’s often difficult for us non-degreed designers to know where to stop. Most want to do the best for our firms, satisfy the requirements of the reviewing agencies and end up with a set of plans that the contractor can use for something other than keeping the mud off of his floorboard. Time is certainly a driving factor. We all should know that Autocad is unforgiving of error. For example, if something doesn’t close by a mere .001, it still doesn’t close…
Engineers and Surveyors must remain educated in the software’s abilities and active throughout the plan production process. If “pretty pictures” matter to the reviewing agencies and contractor, then we have to jump through those hoops. If it doesn’t adversely affect the construction we need to get past “personal preference” or at least know to figure time in to achieve “roundness” or training for a long-term solution. Sometimes the guys in the field know more about the subject of moving dirt then the designer, sometimes not.
Professional Judgement is critical.
Knowledge is key.
Too often the algorithm is substituted for both.
Too many topography surfaces that start a swale only to abruptly stop but continue on the other side of the of unflipped face. Too many hockey stick boundaries. I could go on.
Dirt may still be dirt – and hopefully water still runs downhill.
Oh, THAT thread – I was reading it just a few minutes ago. I liked the basement/foundation level idea for design surfaces, but for EG I’d just make a white hatch within the building shapes & put the surface behind the hatch.
Hey, Matt – you’re absolutely right – you have to know how to spot algorithm-based surface anomalies, how to fix them… and you have to know the site to spot the cases where the “anomaly” correctly models the surface.
Sawtooth berms/swales is the most common surface error I see, usually from lack of breaklines. My favorite example was the stream that got turned into a series of ponds because the def had *no* breaklines.
When you change outsourced topographic survey data you throw out your contractual ‘hold’ on the surveyor. If he gives you wrong topo because he didn’t inspect the end product closely enough or he doesn’t know how to use the software, shame on him. Send it back for a no-charge correction. We rarely have time for that, but if you change his work, you are not using his work. When you change his work, you make it your own and any liability that arises from loss or damage caused by the error lands in your lap. If such errors occur in survey consultant’s work or your in-house crews, these people need to be re-trained and held to whatever standard you set. The best system begins with standardized survey point coding by which the software can automatically add breaklines. Then minutely inspect the surface to see it is properly presented. If not, revise, add or delete breaklines & flip triangles etc. until it’s right. Being a surveyor, I know we’re a surly lot and hate to be told how to do our work. I want to invent a total station survey instrument with a digital camera feature to photographically document what the point code attempts to describe.
Digital cameras and voice recorders are great ingredients to add to the survey stew. John Cobbs idea is as brilliant as beer in bottles! A “smart rod” that downloads back to the collector can’t be too far in our future (can it?)!
The sites that we design to the hundredth of a foot, is put in by a guy running a dozer with 4″ teeth.
You could flip a face on the surface and have a contour go from this /\ to \/ .
Havn’t been following the groups this week, been busy on other things, but we must be doing something right: just obtained our first 7, thats right, 7 figure surveying contract. neener…neener…. 🙂
Just read John Cobb’s equipment wish above and I believe you are describeing the next generation Trimble equipment.
For the record, Topcon has had built-in digital cameras for a number of years, and most laser scanners have them as well – those that don’t scan in photorealistic quality.
For the record, I had been a Topcon user for around 20 years, but there poor service forced me to go to Trimble. When the Topcon help desk had no one that knew anything about and no record of documentation of a 5 year old GPS system we had spent $50,000 on, we decided enough is enough. I no longer consider Topcon a viable alternative….