Geotech contractor data for 3d interpolation with Geostatistical Analyst

[GISDataTasPorts]

I'm an experienced ArcGIS Pro user, but completely new to geotech and the 'Geostatistical Analyst' toolbox (for which we have not yet purchased a license).

I would like to use the 3d interpolation tools in the Geostatistical Analyst toolbox to generate 3d models from geotechnical works performed by contractors.  The interpolation tools require a feature layer as input, which must be a 3d point layer with an attribute to be interpolated.  I have two questions around this input layer...

1. Our geotech contractors who perform borehole investigations do not usually supply us with spatial data like this.  What sort of data formats are geotech contractors used to supplying that I could easily convert to this?  (Eg, CSV/Excel?)  Ie, what should I ask for that would be understood and accepted?
2. When they supply such data, it is the elevations where the strata changes within each borehole which is critical (eg, from soil to clay, from clay to bedrock).  However, a point would have just one such strata type attribute value, I guess (either soil, or clay or bedrock).  How would this be managed in such a dataset?  Is this done by generating two points at almost the same location?  Eg, a soil point 1mm above a clay point, and a lower clay point which is 1mm above a bedrock point?  Or another way of looking at it would be... 2 points for each strata type (per borehole), one for the top of the clay layer and one for the bottom of the clay layer.

Thanks for any insight you can provide for a geotech newbie.

[sjones_esriau]

Hi there,

I've seen drillhole and borehole datasets delivered in a variety of formats and schemas, depending on the type of measurement being captured. Regardless of the source format, the objective is generally the same: derive the real-world 3D location of each observation, whether that's a discrete measurement (such as an assay, temperature, salinity, or geotechnical reading) or a geological boundary (for example, a stratigraphic horizon or water table surface).

From there, ArcGIS can be used to create 3D visualisations and analytical products, including voxel layers for continuous subsurface modelling or multipatch geometries representing geological volumes and strata.

Discrete Measurements

For point-based observations, data is commonly provided as:

• Unique ID
• X, Y coordinates
• Surface RL (elevation)
• Depth to measurement

Using these fields, you can calculate the absolute elevation (Z value) of the observation and generate a 3D point feature representing the measurement location. Once a set of 3D points has been created, Geostatistical Analyst can be used to interpolate and generate a voxel layer that visualises the subsurface phenomenon in three dimensions. The workflow is demonstrated here: Turn your borehole data into a complete exploratory 3D model in three easy steps

Geological Layers and Boundaries

For stratigraphic horizons, aquifers, water tables, or similar layers, the typical approach is to generate separate surfaces representing the top and bottom extents of the layer. These surfaces can be modelled as TINs and subsequently converted into multipatch features, enabling volumetric visualisation and analysis within ArcGIS Pro. This workflow can be achieved using standard 3D Analyst capabilities and is outlined here: Create a 3D subsurface visualization of aquifers

From a data preparation perspective, workflows are often simplified when the X, Y coordinates and elevation values for both the upper and lower boundaries are provided within the same table. However, some attribute processing is usually required regardless of the source structure to derive the final 3D geometry. Where data is delivered in a consistent schema, the entire process can be automated using ModelBuilder or Python to support repeatable ingestion and update workflows.

Considerations

• Many subsurface visualisation workflows assume a vertical borehole and therefore provide an approximation of the true measurement location.
• In practice, drillholes are often deviated or curved. Where downhole survey data is available, more advanced borehole desurveying techniques should be used to calculate the actual 3D position of measurements along the borehole path.
• Ensure vertical coordinate systems are correctly defined and aligned with the horizontal coordinate system.
• Verify elevation and depth units are consistent throughout the workflow (for example, metres versus feet).

In summary, the key requirement is to derive the absolute 3D location of each measurement or boundary. Once those 3D features exist, ArcGIS provides several options for modelling, visualising and analysing the subsurface environment.