Interpolate the level from the ground surface!!

[Phiphi]

Saiswaroop, just feel free to post your questions here so that you can get help from many members and everyone gets learning as well. Cheers, PP.

[BIGAL]

Ok here is the maths answer

 

As you can see the height of a point can be calculated from the other 3 pts if using lisp pick Pt1 Pt2 Pt3 Pick actual Pt.

 

make Pt1 top of traingle you know the angle of pt to Pt1 so can calculate new intersecting Pt then work out its level then work level to circle based on Pt1

[badien]

Thanks BIGAL for you helps, could you explain a little more in details.

In my opinion, if we can get z co-ordinate of pt from 3 points pt1, pt2, pt3, we have to create a plane equation from these points (pt1, pt2, pt3), from this equation we can replace x, y co-ordinates of pt into this equation and get z co-ordinate.

Is that right or wrong? Help me!!

All your time is much appreciated!

[CarlB]

Is that right or wrong?

 

That's right

 

http://mathworld.wolfram.com/Plane.html

[Charles Roberts]

Here is more detail:

 

Equation of a plane

Ax + By + Cz + D = 0

 

where vector [A,B,C] is normal to the plane, (x,y,z) is a point on the plane, D is a constant.

 

To find the normal, calculate the vector cross product of two triangle edges such as pt1->pt2 and pt1->pt3 and normalize the result to length 1.

 

Now you can calculate the plane constant D since any point that is on the plane can be used (you already have three: pt1, pt2, or pt3).

 

Solve the above for z:

 

z = (-Ax - By - D) / C

 

A,B,C,D are known, x,y are the 2D coordinates for the unknown point, and z is the unknown elevation you are trying to find

[joan]

Hi!! im using autocad 2008 your posts are very interesting could you please hep me i already download site topo and i have a drawing in autocad with lot of points, they do have z elevation how can i import them into sie topo?? i would like to make a surface with them i don't know what is autolisp... please heelp............

[advex]

TopoLT is an application for those who design topographical or cadastral plans in digital format.

Search tag: Topolt - 3dspace

[joan]

could you please give me some more details?? in the first page of this topic badien had the same problem and member phiphi gave him a perfect solution...this is what i want to do ...phiphi gave some steps, they seem so simple but i don't know autolisp so i can't extract my drawning with the points as .csv format so i can import it into site topo program ...... i really need your help thank you a lot!...

[Charles Roberts]

i have a drawing in autocad with lot of points, they do have z elevation

 

What kind of points do you have? If you 'list' a point object, what does it say?

[joan]

Points in autocad with x,y,z coordinates...

[Charles Roberts]

Then the steps given for badien should work.

 

To use the lisp program:

1. Get a copy of exptxt.lsp and put it somewhere like c:\lisp\exptxt.lsp

2. In autocad, type (load"c:/lisp/exptxt") - note the slashes slant forward

3. You now have a new command, exptxt. Run that and select all the points.

4. It should prompt you for a place to save the text file of xyz coordinates.

 

The rest is the same advice for badien.

[joan]

exptxt.lsp what is this file and where i can find it to make a copy into c???

[Charles Roberts]

Look at the 5th post in this thread by PhiPhi.

[joan]

ok, i did that ...than i opened this txt file with excel to save it as .csv but something went wrong..i think its somethings with the commas or the tabs ...anyway i m in a good way.... Really thank you for your time (and i'm sorry for my english)

[Rikkert]

Phiphi,

 

I've tried the steps above but don't succeed in getting the right result... Could you help me solve this problem?

I've attached the dwg-file so maby you can immediatly see the problem. Could you maby send a printscreen of how the coordinates-list in excel must look like?

plan site.dwg

 

Thanks in advance,

Rikkert

[GP_]

Have you tried with DTM and AutoCURVE?

 

http://www.cadtutor.net/forum/showthread.php?53184-topography-survey-points&p=360367&viewfull=1#post360367

[motee-z]

have a look to this lisp i improve it using this forum

you will see two way to find z level if you select three points which form the head of 3dface then you can pick any place inside 3 points you will get printed level with the new point next way if you select all points in a drawing then you pick any where the lisp will search for the nearest 3 points then mark them with a circle then print the the z level but this way not accurat enough because it may go outside the 3 points

evenv.LSP