Filtering Duplicate Points with Different Levels

Whilst our tools for point cloud solutions are very powerful, much of the everyday work will fall on basic tools available in ⁿ4ce.  This Tips and Tricks will look at how you can isolate points with different heights having the same XY coordinates.  This may be of use to people extracting data from BIM models.

In the example below we have a grid of levels taken from a building on four levels, with over 1000 points in total.  We need to separate each floor and analyse levels to detect the highs and lows.  

Duplicate Points but on Different Floors

3D view of Points

There are many ways to edit your data in ⁿ4ce.  This is particularly helpful if you can do  this simultaneously spatially both graphically and in text form, the later normally being in spreadsheet form.  We call this Duality of Display and Edit.

For this exercise we will view and edit our data using Data Grids (spreadsheet).  With XYZ coordinate data this can be accessed from the Project Tree using either Coordinates or Models.  Here, we will use a Coordinate folder as the editing tools we need are present here, namely Order and Filter points. 

Note, whilst Model folders have ordering tools these are restricted to Codes and Numbers which help stringing of coded or numbered data to form features.

Let’s look at the Coordinate grid of points.  In the example below we have a folder on the Coordinate Tree called Combined Floors being the one we wish to sort.

Control Grid of Combines Points

Right clicking over the Grid will bring up an edit menu.  This menu is column sensitive and options available will depend upon which column you click over.  In the above example we are interested in editing heights.  After right clicking select the Order option.  This will re-arrange all the points in ascending height order, with the lowest at the top of the list.  It may be possible to identify the points from different floors at this point, but we will let ⁿ4ce do some of the work for us.

Right click and use the Reverse All option to put the highest levels at the top of the listed points.

Right click over heights again and select the Filter option with a search radius of 1mm (0.001).

XY Duplicate Point Filter

Filtered Points

A list of duplicate points will be presented in a report (Notepad type editor) with all the duplicates being highlighted in the grid.  The unhighlighted points being the duplicate points with the highest level, since the column was ordered highest to lowest.  Use the options in the right click menu to Reverse selection then Cut and Paste the highlighted points to a new Model folder, called Floor 4.

Note, If you need to clear the highlights use the blank icon at the top of the line count column.

Repeat the process to identify the remaining three floor levels.  Now we can look at levels on Floor 4 to identify highs and lows.  In graphics, select DTM and form the triangulation.  To see the contours, set the Normal contour default interval to 0.01m.  You should see something like below.

Floor 4 Contours (0.01 interval)

To see the surface undulations in colour, turn on the Shading [ALT+F9].  If the colour is solid you will need to change the intervals by go to DTM Settings, as shown below.

Setting Shading Intervals

A shading table can be added by going to the Tools menu.  You may have to play around with setting to get the right sizing here.

What is required now is to identify the height depths from a datum of 99m, on floor 4.  The easiest way to do this is to subtract 99m from all points.  This is best done from the Model Grid.

Reducing Levels by -99m

Return to graphics to see the shading and levels have been updates, but the shading table will NOT be updated, if present.  This needs to be deleted and replotted.

New Shading to a Datum Level of 99m

To complete this exercise, we will calculate the volume of material to make up the surface to 99m.

Selecting Prism Volumes from the DTM menu.  Since we have already removed the -99 datum the datum height needs to be set to zero.  The Report that appears tells us that we need 54cm to bring up the levels to 99m.

Note, the datum value displayed is always the lowest level found.

Please be aware there is a Case Study that goes into Height Dipping in more detail.

AiC Support team.
April 2020