Page 27 - Geochemical Anomaly and Mineral Prospectivity Mapping in GIS

Geochemical Anomaly and Mineral Prospectivity Mapping in GIS
by E.J.M. Carranza
Handbook of Exploration and Environmental Geochemistry, Vol. 11 (M. Hale, Editor)
© 2009 Elsevier B.V. All rights reserved. 23

Chapter 2

SPATIAL DATA MODELS, MANAGEMENT AND OPERATIONS

INTRODUCTION
Geochemical and other types of data sets for target generation in mineral exploration
are spatial (or geographically-referenced) data that come from either primary or
secondary sources and are stored in either digital or non-digital (analogue) formats. The
diversity in storage formats of such data sets calls for proper data management in order
to achieve efficiency in modeling of geochemical anomalies and prospective zones via
various forms of spatial data analysis. Target generation in mineral exploration thus
requires a computerised system such as a GIS so that the pieces of spatial geo-
information of interest are mapped as discrete spatial entities or geo-objects (i.e., with
perceivable boundaries, sizes and shapes). In a GIS, geo-objects are represented either as
vector or raster spatial data models. The range of operations for spatial data analysis
supported by a GIS depends on (a) geometric model of geo-objects (point, line or
polygon), (b) spatial data models (vector or raster), (c) type of attribute data (quantitative
or qualitative), (d) objectives of analysis and (e) GIS software package used. The last
factor is least but must be considered important because many GIS software packages
that are available at present support certain types of spatial data analyses using either
only vector or only raster spatial data models.
This chapter explains briefly the concepts of spatial data models, especially which
model is appropriate for representation of certain types of geoscience spatial data in a
GIS, and the concepts for capturing and organising spatial data in a GIS database. The
various types of GIS operations for spatial data analysis are also discussed briefly,
because these will be the topics in the succeeding chapters.

MODELS OF SPATIAL DATA
The definition of model in this context is different from the definitions given in
Chapter 1. In the present context, a data model refers to (a) the schema or ways of
organising data about real-world systems or (b) the symbolic representation of
relationships between geo-objects and their data attributes.

Geo-objects
Many types of geological features with distinct boundaries, such as lithologic units,
are clearly geo-objects. There are several types of geological features with no distinct