The Drillholes module in Discover can use drillhole data captured in a number of different formats. Discover can use drillhole data stored in any database format that MapInfo can read, including Access and ODBC databases. Discover does not need to make any alterations or additions to the source data.
Discover calculates 3D coordinates for downhole samples when it displays the drillhole, which means that it is not necessary to store these coordinates in the original data tables. This improves ease of use with Microsoft Access database tables and read-only tables (such as Excel spreadsheets). Also, changes to the collar coordinates or to the downhole surveys do not require downhole coordinates to be recalculated.
Drillhole data is stored in a number of related tables, with the Hole ID acting as the key to link the different tables. Some or all of the following data tables are used to define the project.
Collar Table
The collar location table is a mappable table containing point objects for each drillhole collar. The collar table must include the following columns:
• HoleID • Easting • Northing • Elevation
• Total Depth
If there is no separate downhole survey table then the collar table must contain two additional numeric columns for drillhole collar Azimuth and Dip. Dip may be expressed as positive or negative values eg -90 or 90°
Any other data columns are optional. All columns must be numeric aside from HoleID which may be a text field. For native MapInfo tables it is recommended that coordinates are stored in columns with a Float (Floating Decimal) data type.
Note The actual names and order of the mandatory columns is not important, as to the columns are nominated during project setup.
Downhole Survey Table
The downhole survey table is a non-mappable table that contains a list of depths and surveys for each drillhole. This table is optional but if available must contain the following columns:
• HoleID • Depth • Azimuth
74 Encom Discover 3D Workshop Manual
• Dip
Depth, Azimuth and Dip columns must be numeric and dip values may be positive
or negative. It is unlikely that other data is included in this table and Discover does not check for any other columns.
Drillholes having no downhole surveys are displayed as straight lines using the
Dip, Azimuth and Total Depth values from the Collar table.
Note The actual names and order of the mandatory columns is not important, as to the
columns are nominated during project setup. Downhole Data Tables
Downhole data tables are non-mappable tables that contain geochemical,
geological or geophysical data values for selected intervals down each drill hole. A drillhole project can contain multiple downhole data tables. The downhole data tables must contain the following columns:
• HoleID
• Depth From
• Depth To
Depth From and Depth To columns must be numeric. The position and data type
of the mandatory columns must be the same in each downhole data table. Other data columns (such as sample number, rock type, gold grades etc) may be included as required. Discover can display data from any of the columns in the downhole data tables.
Note In the drillhole project setup the mandatory columns are assigned using the first
downhole table selected. If the mandatory columns in other downhole data tables are in a different column position then incorrect data may appear on the drillhole sections or plans.
Discover enables downhole datasets measured over different sample intervals to be displayed together. For example, Au values may be displayed from 10-11m, 11- 12m, 15-16m, and 18-21m with lithology values from 0-11.4m, 11.4-19.1m, and 19.1-21.0m. Only data that conforms to the same sampling intervals should be stored in the one table. In the above example above two separate downhole tables would be created; one table for assay data and one table for rock type. Multiple downhole data tables may be used as required.
ODBC Data
Discover can use drillhole downhole data from ODBC databases in one of two ways. Using the MapInfo File>Open ODBC connection command, a normal ODBC linked table can be created. This linked table is treated as any other MapInfo table. Alternatively, Discover can directly access just the ODBC data required for a specific section. This greatly reduces the local storage requirements for linked tables and can speed up operations. This manner of data access
requires a special configuration file to be generated for each ODBC table used and is designed for database administrators to set up direct ODBC access.
2D Drillholes 75
Grid and Contour Surfaces
Discover can extract profile information from gridded and contoured surfaces (such as surface topography and soil geochemistry) for displaying in the drillhole section. Grids can be in MapInfo, ER Mapper or Geosoft format. Contoured surfaces must consist of polylines attributed with the appropriate Z value.
Surface Geology
To display a geology layer, an appropriate surface file must also be used. A gridded DEM surface provides the best surface profile however attributed contour data can also be used. When using contour data the surface geology (or polygon) layer is only shown in the area covered by the contour data. Discover does not extrapolate data outside the limits of the topography surface.