Geographic Information Systems GIS Analysis and Modeling 1

Geographic Information Systems GIS Analysis and Modeling

1. Geographic Analysis ► Geographic questions: where, when, why, and how ► The purpose of the analysis is to answer questions about: - what existed at where, when, why, and how - what will happen at where in the future or in other locations

2. Organizing Geographic Data layers (shape file etc. ) ► Feature types: points, lines, polygons ► Object types: geometric or thematic ► e. g. Development streets - line layer 1 water - line layer 2 parcels - polygon layer 1 soils - polygon layer 2

3. Overlay Arithmetic overlay ► Logic overlay ► Weighting input layers ► Raster vs. vector overlay ►

3. 1 Arithmetic Overlay adding layers, subtracting, multiplication, division, etc. ► Raster ► Input data layer A Input data layer B Output data layer

3. 1 Arithmetic Overlay. . ► Arithmetic operation on two data layers using the vector data model Attribute data Spatial data Input data layer A Input data layer B Output data layer

3. 3 Weighting Input Layers Professional experiences ► Expert votes ► ► Empirical or analytical models

3. 4 Raster vs. Vector Overlay ► Raster - Every cell is executed, and the overlay result is a new layer ► Vector - The operation is executed only for areas of interest - New attribute items are created - New layers may be created that carry both the original and new attributes - The operation is generally more complex than raster overlay

Raster Overlay Vector Overlay http: //www. geoict. net/tgipage/Teaching/UNIT%207 --PPT. pdf

3. 2 Logic Overlay ► Finding areas where certain conditions occur ► Boolean logic Mary Ruvane, UNC –Chapel Hill

Union INPUT COV UNION COV # 1 2 3 4 5 # ATTRIBUTE 1 2 102 3 103 ATTRIBUTE A B C D OUT # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 INPUT COV # ATTRIBUTE 1 1 2 A 3 B 4 C 5 D 1 UNION COV # ATT 1 2 102 1 3 103 1 2 102

Intersect and Identity ► Intersect ► Identity

Clip

Erase

Update

4. Proximity Analysis (Buffering) ► The identification of a zone of interest around an entity or a set of entities

Buffering http: //www. sdsmt. edu/online-courses/geology/mprice/geo 416/lecture 9. ppt

Buffering A single distance buffer (250 m) A multi-distance buffer (each ring is 150 m) http: //geology. wlu. edu/harbor/geol 260/lecture_notes/notes_location 1. html

5. Measurement ► ► ► Distances between points Nearest distances Functional distances Lengths of lines Perimeters and areas of polygons Centroid of an area Area of a profile Volume Shape Narrowest and broadest distances across a polygon Sinuosity of a line

5. Measurement. . ► Distances between Points - Euclidian distance

5. Measurement. . ► Nearest distances The Closest Facility

5. Measurement. . ► Functional Distance Three-minute response time from a fire station, City of Phoenix http: //www. esri. com/mapmuseum/mapbook_gallery/volume 17/public 2. html

5. Measurement. . Lengths of lines ► Perimeters and areas of polygons ►

5. Measurement. . Centroid of an area ► It is used to represent a polygon by a single point ► Several methods to identify a centroid: mean value of vertices’ coordinates, center of the enclosing circle or rectangle, ► http: //www. geoict. net/tgipage/Teaching/UNIT%207 --PPT. pdf

5. Measurement. . Area of a profile ► Volume ►

5. Measurement. . ► Shape - how to measure shape of an area? - a compact shape has a small perimeter for a given area - compare perimeter to the perimeter of a circle of the same area - shape = perimeter / area ► Narrowest and broadest distances across a polygon

5. Measurement. . ► Sinuosity of a line - the ratio of the actual length to the straight line length between point A and point B

Readings ► Chapter 5, 6, 9, 10