Terrain contour. Flat area that slopes in two directions.

[dvogel1]

Hi. I'm trying to create a terrain plane that slopes in two directions. To visualize this hold a flat object (notebook) so that it is a horizontal plane. Then rotate one edge down a little. That's sloping in one direction. Now rotate an adjacent edge down. Now it's sloping in two directions. That is, all four corner points are at different elevations. Ideally, there would be a tool to draw a rectangle and then define each corner to be at a different elevation. Without that tool, how can you do this?

 

Thanks, Don

[robdyck]

Open Help, search "terrain" and then "elevation data".

[HumbleChief]

13 minutes ago, dvogel1 said:

Hi. I'm trying to create a terrain plane that slopes in two directions. To visualize this hold a flat object (notebook) so that it is a horizontal plane. Then rotate one edge down a little. That's sloping in one direction. Now rotate an adjacent edge down. Now it's sloping in two directions. That is, all four corner points are at different elevations. Ideally, there would be a tool to draw a rectangle and then define each corner to be at a different elevation. Without that tool, how can you do this?

 

Thanks, Don

Have you tried it? A terrain can be defined in virtually unlimited shapes and manners using elevation points, lines and regions.

[dvogel1]

Yes, I have been working on it. I'm starting with imported CAD data for a complicated, steep lot. I'm trying to modify the region in front of the house to create a slope in two directions to shed water. Ideally there would be an elevation line tool that would allow you to set the elevation at each end.

[robdyck]

25 minutes ago, dvogel1 said:

Ideally there would be an elevation line tool that would allow you to set the elevation at each end.

I've suggested that to Chief at least a few times. Instead, you can replicate an elevation point at a set distance in some or all o the x-y-z axis. If you know the distance and elevation between 2 points, it is simple to replicate an elevation point at a % slope. For instance, copy  / replicate a point 10 times, at 10.0' in the y-axis and 0.1' in the z-axis to create a 10% slope.

For smooth terrain, you may need to decrease the spacing between points to 5' or less.

[dvogel1]

That's what I concluded. The plane I described can only be created by a large number of individual points. Thanks for suggesting the automated method. I'll try it now.

[Alaskan_Son]

2 minutes ago, dvogel1 said:

The plane I described can only be created by a large number of individual points

 

I could be misunderstanding having not seen the lot, but I disagree.  Typically less is more with terrain elevation data.  It could take as little as 2 pieces of elevation data; 2 points, or a flat region and a single point maybe...

 

 

[dvogel1]

19 minutes ago, Alaskan_Son said:

 It could take as little as 2 pieces of elevation data; 2 points, or a flat region and a single point maybe...

 

I'll give that a try, but a couple of data points/lines are overwhelmed by all of the existing data and you end up with two little humps/depressions.

 

Here are three pics showing the point grid method. My starting elevation reference is 90' at the intersection of the bridge and the elevated walkway (in the shadow). I don't like having all of those points hanging around, but it works.

[dvogel1]

The point grid revealed the correct (absolutely NOT intuitive) approach. See the attached pic of the terrain with the grid. It shows how the software modified the terrain poly-lines to achieve the outcome. I took a picture for reference, removed the point grid and then modified-added the poly-lines to achieve the same outcome.

 

I had to modify the 87', 88' and 89' lines to closely match what the software produced. I'm guessing that a landscape architect would have said, "duh"!

[glennw]

It may help this process to remember that an Elevation Line is just a series of Elevation Points at about 24" centres.

[Alaskan_Son]

35 minutes ago, glennw said:

an Elevation Line is just a series of Elevation Points at about 24" centres.

 

Curious where you got that number from. 

[Alaskan_Son]

5 hours ago, dvogel1 said:

I'll give that a try, but a couple of data points/lines are overwhelmed by all of the existing data and you end up with two little humps/depressions.

 

That just tells me that you're probably:

A.  Working with too many data points and/or...

B.  Giving Chief conflicting information

 

You're only going to get little humps or depressions like that if you've defined the terrain in the adjacent areas incorrectly. 

 

Like I said, less is more.  Start simple and then add data as necessary to refine.

[Alaskan_Son]

5 hours ago, dvogel1 said:

The point grid revealed the correct (absolutely NOT intuitive) approach.

 

Ironic, because that's how we've been showing topography on just about every map and drawing produced for the last 100 years. 

 

5 hours ago, dvogel1 said:

I took a picture for reference, removed the point grid and then modified-added the poly-lines to achieve the same outcome.

I think the general method you decided to try out was a really good one (the idea of simply copying automatically produced elevation data that you're happy with).  I would however suggest that you can simply trace over the elevation data before deleting your points instead of using a picture.  You could also optionally create a CAD Detail From View and then use that for reference.

[glennw]

56 minutes ago, Alaskan_Son said:

Curious where you got that number from

I got it directly from Chief many years ago, I think when they were first introducing terrains

It is something I have always remembered 

[dvogel1]

16 hours ago, Alaskan_Son said:

Ironic, because that's how we've been showing topography on just about every map and drawing produced for the last 100 years. 

 

I think the general method you decided to try out was a really good one (the idea of simply copying automatically produced elevation data that you're happy with).  I would however suggest that you can simply trace over the elevation data before deleting your points instead of using a picture.  You could also optionally create a CAD Detail From View and then use that for reference.

 

Tracing over the resulting contour lines is a good idea, thanks.

 

This is my first project. It's complex and so is the software (probably no worse than other software packages). It was a significant challenge just importing the survey CAD data from a file that has 27 layers, and understanding how CA presents it. It's only as complex as the surveyor provided. The property undulates and drops 100 ft over 230ft. Manipulating the data is just the latest, very steep learning curve.

 

I also have the terrain data file (202 points). In some ways it's easier to make modifications with the points instead of polylines. I chose to use the CAD file instead because it includes tree locations, utilities, etc. Would you recommend using the terrain data instead of the CAD file?

 

I have used Autodesk Inventor to design machines and it's frustrating to use CA and have such limited ability to work in the XZ or YZ planes. That's one more challenge to deciding what going on with the terrain.

 

[dvogel1]

Another question just came to light. Is it possible to hide the terrain contours inside the footprint of a structure?

[Alaskan_Son]

8 minutes ago, dvogel1 said:

Another question just came to light. Is it possible to hide the terrain contours inside the footprint of a structure?

 

You should start another thread when you have new questions, but yes, there are multiple ways. Here are a few:

• Select Terrain, Open Object, check Hide Terrain Intersected by Building
• Select Terrain and click Make Terrain Hole(s) around Building(s)
• Use the Terrain Hole tool to manually draw your hole in the terrain

[dvogel1]

The custom hole seems to be the best option since I don't want to hidden any of the terrain in 3D views. Thanks

[Alaskan_Son]

2 hours ago, dvogel1 said:

I also have the terrain data file (202 points). In some ways it's easier to make modifications with the points instead of polylines. I chose to use the CAD file instead because it includes tree locations, utilities, etc. Would you recommend using the terrain data instead of the CAD file?

 

No, not necessarily.  I think using the data file as a starting point is a great method that can save lots of time.  As you've discovered, sometimes you just need to replace some of the data points with more appropriate objects.  A couple of the more common things we run into are more elevation lines/points than are necessary (just delete some) and overly segmented terrain elevation polylines (replace with lines or simplified polylines).  No matter what though, we can certainly use the imported data as a starting point...it just typically needs a bit of cleanup is all.

[dvogel1]

Thanks. I think I'd rather use the data and import only some of the CAD file layers. Live and learn!