I would normally use 250mm contours (approx 1') for most topo jobs, but where the hard surfaces are flat and an accurate form needs to be depicted to identify areas which might pond then I set a closer contour interval for those areas only (perhaps 50mm, about 2").
Exactly!!!
It's just here in the USA it's: we've always done it this way and we are always going too. 😉
Shoot everything to allow the software to interpolate the contours.
Let the contours tell the overall story...
Then SUPPLEMENT the contours with spot elevations to provide DETAILS.
An engineer can obtain data from the surface modeling structure.
But is engineering not much easier when data is visually sufficient to design from...
A review of the provisions for photogrammetric national map accuracy standards gives some guidance.
"I may or may not include contours on road surfaces, concrete etc."
Steps are not part of the topography unless they flow with the land. Then, yes, you contour the steps. If they are up to a dock, or other elevated feature, then you do not.
Perhaps you need to review the definition of "topography". ALL topograhy is contoured. Elevated, man -made features are generally not called "topography".
In the "flats" the contours are supplemented with spot shots.
You have to be able to tell the differance between "plannimetric" features and topographic" features. That will generally tell you where you need contours.
Take a look at older USFS topographic quad maps for examples of quality contouring. Contour display should vary as a function of slope. The key is to have index contours at, say 5 feet, and intermediate contours at, say 1 foot. Write the specifications such that when the index contour spacing is less less than X depending on map scale, intermediate contours shall not be shown. Index contours are one line weight heavier than intermediate contours. Adjust to suit, 1 foot index contours with 0.2 foot intermediates in flatter country, for example.
Pepper the really flat spots with spot elevations where necessary, and Bob's your uncle.
I agree, show spot elevations in flat areas. If the client wants more precise contours the field work changes and needs a new contract.
No disdain here, just business sense. For instance, one might get a contract to topo a basketball court. NCAA has guidelines for flatness. So you grid it out and take shots every inch or so and show half inch or so contours (don't remember the details). If the court doesn't pass, then the college must replace it.
But you gotta have the data to back up the presentation. Spot elevation is the only way to achieve that if the contracted for specificity is not showing areas of concern and the client does not want to spend more money.
If we're doing contours, we do everything.
> Perhaps you need to review the definition of "topography". ALL topograhy is contoured. Elevated, man -made features are generally not called "topography".
Definition or regional use of a word?
In definitions, I see many references to "man-made" features.
:good:
Christ has a great example. That crown in the road really shows up nicely.
Exactly!
Actually, we only contour the easy surfaces. the hard surfaces, we just fake the contours. We will usually put some big jags in them to make them more realistic.
Perhaps I have received bad training, but in this country (not USA) every topo I have seen does not have contours on the roads, concrete etc. Needless to say I will put them on everything from now on.
I am here to improve both myself and surveys. Thanks to all the useful non-judgemental comments. To the other 2 I should have known better from previous posts I have seen and chosen my words more carefully, I hope it wont deter others potential posters.
Contour everything, and if they want it into Revit, then you may have to look at giving them a file with just the contours on a very tight interval. (eg, 2cm contours).
Revit is pretty basic at bringing in topo.
:good:
good and interesting post.
one more question, do you mind sharing your country?
Christof.
No sir, that's the way YOU interpret it. Yes, man-made features are shown on topographic maps, but they are called "plannimetric features" and are not part of the topographic surface depicted on the map. The topographic features are the elevations and contours depicted thereon.
I have been a cartographic drafter since 1968 and have drawn topographic maps of areas from the Middle East to Viet Nam, Thailand, Cambodia, Puerto Rico and all across the United States. Every thing from 15' quads, 7.5' quads, JOG Charts, aeronautical maps all the way down to local site surveys.In all of those maps for many different agencies, what I have stated here is the rule and the norm in the map making profession. Just because some rookie surveyor cannot understand those concepts will not change the way a topographic site survey will be performed.
I appreciate your input and will take it all onboard. I would just say that I am doing things the way I learned from a previous employer and viewing other peoples drawings here. Perhaps it is just the way it is done here (even if that is wrong). If you feel the need to insult me because of that then I don't know....
I am sure you did not wake up one morning and know everything. I personally find that I learn new things each day and I constantly aim to improve my work.
Perhaps this thread is an example of why many lurk rather than post.
