Introduction to Open Source Gis Course for Irish Archaeology Institute of Archaeologists of Ireland – CPD Course Gianmarco Cattari www.you-gis.com 1 Saturday 12th of November 2011

GIS = Geographic Information System A Geographic Information System (GIS) is designed to capture, store, manipulate, analyze, manage and present all types of geographically referenced data. In the simplest terms, GIS is the merging of cartography, statistical analysis, and database technology. GIS may be used in archaeology, geography, cartography, remote sensing, land surveying, public utility management, natural resource management, precision agriculture, photogrammetry, urban planning, emergency management, environmental contamination, landscape architecture, navigation, aerial video and localized search engines. 2

GIS data formats VECTOR GRAPHICS is the use of geometrical primitives such as points, lines, curves, and shapes or polygon(s), which are all based on mathematical equations, to represent images in computer graphics. Vector graphics formats are complementary to RASTER GRAPHICS image is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium. Raster images are stored in image files with varying formats. Vector graphics are stored as mathematical expressions as opposed to bit mapped graphics which are stored as a series of mapped 'dots', also known as pixels (Picture cells). 3

Vector files Points Lines Polygons Archaeological Sites National Roads Town Boundaries 4

Combination of vector files 5

GDAL and OGR libraries The Open Source Geospatial foundation The GDAL (Geospatial Data Abstraction Library) is a translator library for raster geospatial data formats that is released under Open Source license by the Open Source Geospatial Foundation. GDAL raster format list The related OGR (OpenGIS Simple Features Reference Implementation) library (which lives within the GDAL source tree) provides a similar capability for simple features vector data. OGR vector format list 6

Raster Data 7 Digital Elevation Model (DEM) Hillshade Model Aerial Photo Scanned Archaeological Plan Orthoimage Lidar Survey