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9: MINERAL EXPLORATION DATA 185

and can be easily filtered out. Each geologist mapping. However this situation is changing
and mining or processing engineer knows what rapidly with the advent of inexpensive portable
the database should contain in terms of ranges, digital assistants using a stylus for input and
values, and units. It is a simple matter of set- better quality displays.
ting up the validation tables to check that the
data conform to the ranges, values, and units
expected. A simple example would be ensuring Digitization
that the dip of drillholes is between 0 and −90 Spatial data are normally digitized either by
degrees for surface drilling. scanning a map or by using a digitizing table.
Documentation for the database is essential In the digitizing table method a point or line is
including the source and method of data entry entered by tracing the position of a puck over
as well as their format. It is essential to main- it relative to fine wires within the table. The
tain adequate, long-term archiving and access. position of the point or line is then converted
For contingencies, it should be possible to add by software into the original map coordinates
fields and columns to the database should it be from the position measured on the table. Trac-
necessary to add information at a later stage. ing lines is very laborious and maps often have
The database should also be capable of mani- to be simplified or linework traced to avoid
pulating all data and the ability to evaluate and confusion during the digitizing process. The
review the data is essential. scanning method has become much easier with
Normally a single, maintained, flexible and the advent of inexpensive scanners. In this
secure storage source is recommended. This method a georeferenced image is traced on a
means that only the most recent copy of the computer screen using a mouse or puck. When
database is being used for evaluation at the the map or scan has been digitized all linework
mine site with older versions archived regu- should be carefully edited. Generally this edit-
larly. Multiple access to the database, even ing is laborious and more prone to errors than
from other sites, can be achieved through web the original digitization.
technology. The additional advantage of such
web technology is that different sets of data,
each containing information about a particu- Attribute data
lar item such as a borehole, can be available Attribute data can be captured by typing hand-
through a single search interface (Whateley written data or by scanning data that is already
2002). The ultimate long-term storage however typewritten and relatively clean. The scanned
remains paper and a hard copy should be images are then converted into characters for
regularly filed of all important data sets, e.g. storage using optical character recognition
drillhole logs and assays. software. This software is however not perfect
and the resulting characters should be carefully
checked for errors.
9.1.5 Data capture
The capture of attribute data is usually relat-
ively straightforward but spatial data is often 9.1.6 Data sources
more difficult. Most field data are now gener- Sources of digital data have become widespread
ated in digital form but any data only available and much less expensive over the last 10 years.
on paper will require digitization. In particular there are digital topographical
(ESRI 2004, Globe 2004), Landsat (Geocover
2004, GLCF 2004) and geological map cover-
Field data capture
ages of the world, albeit at small scales (GSC
Capture of data in the field using computers 1995, Arcatlas 1996). In North America and
is becoming routine often using ruggedized Australia most geological, as well as airborne
computers that can be easily transported. At geophysical data, are available from the na-
present this approach is widely used for routine tional or provincial geological surveys for the
tasks such as sample collection and core cost of reproduction or freely across the
logging but is less well suited to geological Internet. The reader is advised to make a search