GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Queries can be used: to check data correctness to obtain info as steps in analysis Using GIS for Analysis

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Spatial query: Select by theme Structured query language (SQL) SELECT FROM WHERE with constraints … inside, intersects, contains, nearness, adjacent what is here?

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Query builder Boolean operators - AND, OR, NOT A AND BA OR BA NOT B Attribute query:where is this?

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl 1)Proximal search 2) Overlay analysis 3)Best path analysis and routing Kinds of analysis

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl 1)Proximal search - the region of interest is defined in terms of its proximity to an existing feature

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Buffers can be made around points, lines, or polygons. point line polygon

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Proximal search problem: Which hotels are within 200 m of a major road? Methods: a) measure the distance from each hotel to a major road and then select those < 200 metres. b) produce a buffer zone extending 200 m around major roads and perform a ______________ query to find the hotels falling within it. point-in-polygon

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl 2) Overlay analysis - the search for locations that have combinations of attribute characteristics

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Siting criteria for a nuclear waste repository ThemeCriteria GeologyChosen site must be in area of suitable geology AccessibilityChosen site must be easily accessible PopulationChosen site must be away from areas of high population density Land UseChosen site must be outside any areas designated for conservation value Source: Heywood et al. Table 6.3

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl 3)Best path analysis and routing - for problems of shortest or least-cost route between two locations a) network data models for defined paths like roads and rivers b) grid-based raster data models for finding paths across areas where there are no pre-defined paths

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl In ArcView, overlay analysis can involve: point in polygon queries line in polygon queries polygon to polygon queries

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl 1) Union:- Boolean “or” - both themes, full extent, all attributes 2) Clip:- Boolean “and” (cookie-cutter) - overlap, attributes of target theme only 3) Intersect:- Boolean “and” - overlap area only, all attributes 4) Merge:- appends one theme to another (“or”) - both themes, only attributes with the same field name as specified theme AV overlay operations:

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Siting criteria for a nuclear waste repository ThemeCriteria GeologyChosen site must be in area of suitable geology AccessibilityChosen site must be easily accessible PopulationChosen site must be away from areas of high population density Land UseChosen site must be outside any areas designated for conservation value Source: Heywood et al. Table 6.3

GEOG 2007A An Introduction to Geographic Information SystemsFall, 2004 C. Earl Suitable Geology Population Density Roads Land Use Select high Population density High_Popdens union Select not high Pop density Geol_Pop clip Geol_Pop_Rd Select major roads Select not conservation areas Create road buffer Suit_Land Road_buff intersect Nuclear Repository Land