Site model does not match contours

[Sabina]

Hello,

 

I've been working on a site model, based on contour lines. I am quite happy with the outcome, because it was my first time and I didn't even know it was possible! But, the site model is not correct. There are a few things I hope someone can help me with! (See screenshots)

 

1. From above the lines do not match: how can I fix this?

2. Even worse: the different "levels"/heights aren't correct and I don't understand why or how to change this. The lowest level should be 0 and the highest 8000, like I put in the settings, I think.

3. Also, when looking from the side, there should be 8 "levels", but it is showing 9.. But when I look from an isometric view, it shows 8 again..

4. Even though I'm quite happy with the result, the surface of the site model could be a bit smoother. How can I do this?

 

Please let me know if you have any idea!!

[michaelk]

What version of VW are you using?

 

Can you post a file with just the DTM?  

[zoomer]

I see it is a pre VW 2018 version.

 

1.

Is an unwanted interpolation.

You can try to add more edges into your Source Data,

so that the neighboring Contours have about the same amount of edges as the problematic

Contour in this area.

Or adding 3D Points between the Contours by using snap hints and the snapping to their middle.

 

2.

Do you use a Layer Height or have moved your site model in Z ?

Edited September 23, 2017 by zoomer

[Urbanist]

The unfortunate and wrong contour generation at concave  parts of the site is an integral part of the Terrain Modeling engine of VW; it might even be called a feature. The larger and more complex the site, the more errors. 

[willofmaine]

@SabinaIt looks to me like you have nine levels in both cases: in your isometric view with the red contours, I think the small triangle near the left side is the "ninth" level, which corresponds with the very short line in your side views.  Also, in your isometric, it looks like each contour is doubled; the DTM seems to be defaulting to the lower of each pair of contours.  Last, try increasing the maximum height to see if the flat top goes away (you can make the maximum height overly excessive, and it's probably best to do so unless you specifically want to limit the height of the DTM to a specific elevation).  So... there are a few random observations for you...

[Art V]

You may want to get in touch with the Benelux support to work out the best way of solving this in your case depending on your underlying model data, ask for Gelde-Aart or Martin as they are the GIS people. I've had a similar discussion and Vectorworks tries to approximate the contours and does a best guess when triangulating the terrain and that sometimes (or often, depending on the model conditions) can cause the effects you are seeing.
 

One comment in general regarding your DTM, unless you have terraces with (near perfect) vertical transitions from one level to another  it is best to have only one contour line for a given elevation. In your case you have two contour lines between the levels at the same x/y position. It is not a problem if the contours overlap on one side, e.g. if you contours share the boundary at the left as that will be vertical anyway, but for the other contours it may prevent some interpretation/triangulation issues and may give a better matching overall shape.

Edited September 26, 2017 by Art V
small editorial update for clarification.

[Sabina]

On 23 september 2017 at 5:12 PM, michaelk said:

What version of VW are you using?

 

Can you post a file with just the DTM?  

It is a 2016 version.. (I'm a student)

I'm not very familiar with terms like DTM (and since my VW is in Dutch..), could you explain this to me?

[Sabina]

On 23 september 2017 at 5:17 PM, zoomer said:

I see it is a pre VW 2018 version.

 

1.

Is an unwanted interpolation.

You can try to add more edges into your Source Data,

so that the neighboring Contours have about the same amount of edges as the problematic

Contour in this area.

Or adding 3D Points between the Contours by using snap hints and the snapping to their middle.

 

2.

Do you use a Layer Height or have moved your site model in Z ?

It is a 2016 version, since I am a student.

 

1. All right, I think I know what you mean. Thank you, gonna try it out!

 

2. No, I haven't moved anything in Z.

[Sabina]

On 23 september 2017 at 6:46 PM, willofmaine said:

@SabinaIt looks to me like you have nine levels in both cases: in your isometric view with the red contours, I think the small triangle near the left side is the "ninth" level, which corresponds with the very short line in your side views.  Also, in your isometric, it looks like each contour is doubled; the DTM seems to be defaulting to the lower of each pair of contours.  Last, try increasing the maximum height to see if the flat top goes away (you can make the maximum height overly excessive, and it's probably best to do so unless you specifically want to limit the height of the DTM to a specific elevation).  So... there are a few random observations for you...

All right, thank you for your message. I have some new screenshots: Instead of min. hight of 0 + max. hight 8000, I changed it to min. hight 1000 + max. hight 9000 and this seems to improve a lot! Also the amount of levels (see red lines and don't mind the little triangle in the left bottom) correspondent in both the top view, isometric view and the actual 3D site model, but there are still some minor differences, that I don't really mind, except for 1 red line sticking out in the middel (see side view), which is the most important part, since we are going to build there. Do you maybe have any suggestions on that?

[zoomer]

Looks good.

You can add some other contours or points in between existing contours if you want to

clean up some special areas.

But looks you still have double contours by using closed Polygons. You only need open Polygons = lines or curves.

Only the upper edge, no lines running back around the Site Models Borders.

(Only the red contours like you see in the 3D Solid Model.

It only works because VW uses the upper of both Contours and ignores the one below.

I would cut and delete those parts.

 

DTM = digital terrain model

(What VW calls Site Model)