Generating accurate Terrain Model using CAD from Site Survey

[KDsnyder]

I did a quick search through the forums for a solution to this so my apologies if this has already been covered. Here is what I've got...

I was sent a PDF of the Site survey that was done previously. The previous surveyor doesn't have the CAD so I can't simply import that data the data I do have does not have contour lines only pin/nail points from the corners of buildings and other important site features.

 

What are some best practices (after I've scaled the pdf in .plan) to getting this to work out right? I've played with adding point markers and creating my own couture lines but it isn't coming out right. any ideas? Thanks!

34786 Calle Loma, Dana Point PDF (1).pdf

[Chopsaw]

I did not look the PDF over too carefully but one thing to watch out for is making sure all of the elevations you use are ground level as surveyors usually measure to the top of features but if you are familiar with the site and know the actual height of the feature that is called out you can subtract  that value from the measured elevation.  At first glance it looks like there should be almost enough information available if you work with it.   You might be right though as the surveyor would have likely done the contours if it was easy.

[TeaTime]

1 hour ago, KDsnyder said:

I can't simply import that data

Oof.

 

It may be a personal thing but I absolutely avoid Elevation Points whenever possible, but given that's exactly what you're given in this PDF, I'd do exactly that - the PDF certainly seems to contain enough of them to make for a decent Terrain.

Since not a lot (if any?) of those nail points are the same height, I would probably avoid trying to use elevation lines/splines.  I would just place Elevation Points starting with the perimeter points, then working inward.

 

The big tip I'd give with Elevation Points is to place one, when its dbx opens, enter its elevation, but before closing out in the Text field, add the %elevationf%  macro

then copy/paste that point to each new location - this will display the Elevation on the plan so you can more easily double check the PDF with what you have in.

(btw the display format on Plan View is controlled via General CAD Defaults "Displayed Line Length Format"...nevermind that it's not a line and thus has no length).

 

Oh also changing the dialog's Number Style to Decimal Feet streamlines entering those values into the dialog.

[KDsnyder]

42 minutes ago, TeaTime said:

Oof.

Ya, Oof is right.

 

Thanks a ton for the help. Doing what you suggested now. Hopefully it all goes well.

 

[glennw]

3 hours ago, TeaTime said:

It may be a personal thing but I absolutely avoid Elevation Points whenever possible

I wholly concur with this statement.

Only thing is..I would continue along with that advice and use Elevation Lines/Splines.

It is so much easier to control the terrain with elevation lines and splines (along with Elevation Regions, etc) in lieu of points.

What I usually do in some cases is print out the pdf and do my own interpolation of the levels - say at 1' intervals - with a pencil on paper.

I then use that as a reference and draw elevation lines, or otherwise do it straight in the plan interpolating the lines as you go.

Once you have the lines drawn quickly, it's not hard to edit them and drag them around as you fine tune them in relation to the spot levels and other Elevation Data.

If it works out for you using elevation points - great, job done.

Just use this advice as a backup in case you don't get the required results using points.

 

 

[TeaTime]

11 hours ago, glennw said:

I would continue along with that advice and use Elevation Lines/Splines.

I totally agree, lines/splines will always generate more consistent contours, but I wouldn't bother with all the rest of that. Once all the points are in the program will make its own contours. Sure they might be weird in some spots where there isn't enough data from the points. But that's when you come in with lines/splines and correct those contours so you don't have to figure anything out on paper or otherwise. 

 

[KDsnyder]

14 hours ago, glennw said:

...It is so much easier to control the terrain with elevation lines and splines (along with Elevation Regions, etc) in lieu of points.

Is there a good video on how to best use all these features together? I've not normally gotten into needing to use the terrain features but this project has sparked a deep desire to want to learn to master this. I don't fully understand how to manipulate the Elevation Regions for example and would love to figure that out.

 

Thanks for all your feedback!