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Need Assistance getting distance from surveyed point to a surface


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If you are looking at plan view, I have a bunch of points surveyed for blastholes:

x     x     x     x     x
  x     x     x     x     x
x    x     x     x     x     x

These points all vary in height.


I have a surface created under hole collars representing the chemical contact between two different rock units.


I'm trying to project a line from the collar of the blast hole, vertically down, to intersect with the surface and determine that length so I can inform the drillers what depth the holes need to be drilled to.


Currently, here's my workflow to get the required depths: Survey the blast hole locations prior to drilling. Come back to the office, import my points from the survey to CAD. Determine the extents of the blast. Extend the existing geologic model to determine the hypothetical depths. The drillers then drill sample holes to determine the depth of the surface and the surface is updated within two days. I then need to go back out to the blast holes and use my survey equipment to stakeout the DTM. I then go back around to the holes and record on scratch paper the depths to the DTM. I then come back to the office and annotate the drawing with the required depths. I then finally plot the drill instructions for the blasthole drills.


I appreciate any and all help!!

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You can add a point it will auto sit on top of the surface taking the z value, then you could compare the two points z values. I rarely add points so will have to remember how. Murph_map you out there ?


Ps you can recall a point by its "Point" number so I will have a look at this for you comparing two points there may be a auto way using label two points.

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"I rarely add points so will have to remember how"....very simple process to add points, it can be done in a number of ways....since the only item changing is the depth you could copy/create a csv, use the excel to calc your difference in depths and you have your adjusted set of points. Import them into your existing database. This way you have a hard copy of your new points and the information can be manipulated outside without effecting existing data. This may help. rlshound

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Great question, sir.


I don't know if Autocad will be able to accomplish your goal, but for sure the free OOTB tools Microdem and Qgis can do it, in one millisecond and error-free.

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There both Geospatial programs.

Not sure they would apply to what the OP question was but they do look interesting.


Another way to add points on the surface - Select the surface - Display POints and triangles.

Slect the surface again and go to the ribbon under Modify - Edit surface - Add point.

Select the existing point and add a point right over it at the depth you suspect the DTM is.

This will make the surface jump down the the new point.

I think thats what your asking?

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There is probably a way of scripting this


Command: _AeccCreatePointRandomPoints

Select a surface :

Specify location


Because you know the list of points you can get the points as XYZ put into excel and compare for the Z, I will see if I can get the auto insert to work.


had ago this is real rough using VL should be able to do nicely the other way is to run the createpts then copy and paste a column of x,y from excel when prompted for points. Final bit just export all points and sort on x y in excel they will appear in pairs and z diff is achieveable. Can you post a dwg simple with a few points


(defun addptsrl ()
(command "295619.034,5778717.880"
(command "_AeccCreatePointRandomPoints")
; pick surface
; then type (addptsrl)
;points will appear

Edited by BIGAL
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Create points for the blast holes.


Copy points and update elevations with the depths.


Create a cut-fill surface.


Label the cut-fill surface.

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I appreciate all of your feedback. I apologize for not being more active as I didn't get notified by email about any updates.


@Bill_Myron: The issue is that I am essentially getting the depths for the second surface at the corners, all of the points in between are unknown.


@JerryG: I think this may be the closest to what I'm trying to accomplish.

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