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  • Frans Basson

GEM4D Version available for download

Updated: Apr 18, 2020

GEM4D Version is a smaller update with a few improvements and bug fixes.

New functionality

  • Added "Ribbon => Mesh => General settings => Precision", which determine the value precision when copying values from the textbox in the bottom panel (right). The default value of '-1' uses the available data 'as-is', and any other number indicates the number of decimal places.

  • All the colour legend bars now have a transparent white background for better visibility of the values when objects are behind the legend bars.

  • Pressing keyboard "SHIFT" now allow the creation of multiple polylines when "Top toolbar => Lines => Digitise polylines" is selected, without the requirement to re-select the button when one polyline is completed.

  • Pressing keyboard "SHIFT" now allow the creation of multiple discs by N points when "Top toolbar => Map Discs => Create map discs => Selection form => Disc type => N points" is selected, without the requirement to re-select the button when one disc is completed.


  • The BasRock-logo at the bottom of the scene now automatically scales up and down depending on the scene size.

  • Changed the location of the closed polyline option under ""

  • Small interface changes to provide better guidance to the functionality.

Bug fixes

  • Copying highlighted text from the bottom panel to the right to the clipboard caused errors - fixed.

  • "Top toolbar => Split & Delete => Split selection out by rubberband" duplicated object that were fully within the selection area - fixed.

  • GEM4D occasionally crashed when in Information Mode, thus when "Top toolbar => Info Mode" was toggled as ON - fixed.

Discussion: Open Pit reconciliation

1 General discussion

Reconciliation refers typically to a comparison between an actual outcome against a planned design expectation. The usual purpose is to either learn from the comparison to improve the outcome, or to quantify the deviation and determine if the result is within acceptable limits.

This discussion is focussing on reconciliation from a geotechnical perspective to determine the amount of cress loss, toe flare, and catch berm capacity. The figure below shows the definition of crest loss and toe gain (or toe flare), which impacts on the surface area of the catch berm.

Schematic cross-section to define crest loss and toe flare

Qualitative reconciliation is quick and easy to evaluate in GEM4D. Load a pit design and as-built meshes and colour the as-built mesh with “Top toolbar => Yellow colour palette icon => Colour on distance from mesh”, or superimposed wall sections (clippings) to compare the outcomes qualitatively as shown below.

Superimposing and comparing section (clipping) lines in parallel view

2 Quantitative reconciliation

The basic concept is to calculate a statistical distribution of the crest loss, toe gain, and achieved catch berm widths.

2.1 Traditional method

This apparently simple task requires a number of manual steps and highly time-consuming in mine design software as many steps are required:

  • Step 1: Subdivide the mesh into straight wall domains.

  • Step 2: Create perpendicular sections for each straight domain at a set interval, typically 5m.

  • Step 3: Manually mouse pick four points on every section.

  • Step 4: Manually calculate and graph the parameters of interest.

2.2 Automated method in GEM4D

The automated process can be done on a selected area, or a whole pit can be done simultaneously with little additional effort. The principle of the automated method is summarised in the figure below.

Automated pit reconciliation principle

The actual and survey lines are subdivided into points; the design lines points are selected very close together, and the survey line points at the interval of interest, 5 m for this example. The shortest distance to the design line points is then calculated for every survey point, and the value stored at the survey point location. The shortest distance will automatically be near perpendicular to the two lines, and the error can be minimised by selecting very short intervals for the design lines. The automated method takes a few steps, but each step is quick to perform, and the whole process can be completed in a few minutes.

GEM4D Strings before and after sub-division
Distance columns added to the data grid
  • Step 1: Obtain the design and survey strings: Obtain the design and survey strings for an area (or even the whole pit) and clean up the survey strings at the locations of interest.

  • Step 2: Subdivide the design and survey strings: Sub-divide the design line into tiny segments, say 5 cm. Sub-divide the survey lines into the interval distance of interest, say 5 m. This is done by selecting the “Split lines into fixed length segments” as shown below.

  • Step 3: Write the survey points out as a CSV-file and load as Marker-data: Hide the design string and write the survey points out as a CSV-file with “Ribbon => Mesh => Export files => Mesh info as CSV => Poly, Line and Point vertices”.

Hide or delete the survey string object, and load the CSV-file as Marker-data with “Ribbon => Marker => Load files => Text (CSV)”.

  • Step 4: Calculate the shortest distances: Select “Ribbon => Marker => Marker actions => Distance => Add grid distance columns”, which calculates the shortest distance between each marker point and the design points and adds three columns to the Markers grid: 1. Obj1_DistXYZ – 3D distance between the two points. 2. Obj1_DistXY – 2D distance between the two points. This is the plan view distance and of interest for our discussion. 3. Obj1_DistZ – Z distance or elevation difference. This can be used to assess the bench elevation compliance to design.

  • Step 5: Post processing of the data: The histogram chart and statistics of each selection is automatically updated with the filtering within GEM4D, and the spatial colour coded spheres could be generated as shown in the figure below. The data can also be exported as a CSV file to be analysed in greater detail using Excel.

Results from the GEM4D interface

Data can be manually filtered within GEM4D for a more detailed assessment for specific areas such as rock type, design angle, shot number and wall domain.

I received many questions regarding open pit reconciliation and hope the above discussion helps.

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