GEOGRAPHICAL INFORMATION SYSTEM UNIT 1 WE-IT TUTORIALS (PH:8097071144/55)
WE-IT TUTORIALS (PH:8097071144/55)
What is GIS A geographic Information system (GIS) is a computer system for capturing, storing, querying, analyzing, and displaying geospatial data. The ability of a GIS to handle and process geospatial data distinguishes GIS from other information systems WE-IT TUTORIALS (PH:8097071144/55)
applications of GIS GIS has been important in natural resource management including land-use planning natural hazard assessment wildlife habitat analysis riparian zone monitoring and timber management WE-IT TUTORIALS (PH:8097071144/55)
components of GIS WE-IT TUTORIALS (PH:8097071144/55)
Spatial Data? Vs Attribute Data? WE-IT TUTORIALS (PH:8097071144/55)
GIS Operations Spatial Data Input (Data entry, Geometric transformation, Projection ) Attribute data management (verification, Attribute data manipulation ) Data display (Cartographic symbolization, Map design ) Data exploration (Attribute data query , Spatial data query, Geographic visualization ) Data analysis Vector data analysis: buttering, overlay, distance measurement, spatial statistics, map manipulation Raster data analysis: local, neighborhood, zonal, global, raster data manipulation GIS modeling (Binary models ”DIFFERENCE ”, Index models “VALUE CALCULATION”, Regression models “DEPENDANCY”, Process models ”RELATIONSHIP”) Binary models A binary model uses logical expressions to select map features from a composite map or multiple grids. Map overlay to prepare for vector query Multiple grid process for raster Siting common application with multiple criteria (example Conservation Reserve Program) Binary models can be used for change detection. Sometimes binary models are used at the beginning stage of modeling. Index Models An index model used the index value calculated from a composite map or multiple grids to produced a ranked map. Selected variables are evaluated at two levels Relative importance, assigning a weight Observed values are evaluated and given scores. ArcView Model Builder Suitability and vulnerability analysis Regression Models Regression model relates a dependent variable to a number of independent variables in an equation. Linear regression is used when the dependent variables and independent variables are all numeric. Logistic regression is used when the dependent variable is a binary phenomenon and the independent variables are categorical or numeric. Process Models A process model integrates existing knowledge about the environmental processes in the real world into a set of relationships and equations for quantifying the process. Universal Soil Loss Equation (USLE) Agricultural Nonpoint Source (AGNPS) Soil and Water Assessment Tool (SWAT) Typically raster-based Most commercial GIS do not offer. WE-IT TUTORIALS (PH:8097071144/55)
Geographic Coordinate System WE-IT TUTORIALS (PH:8097071144/55)
Datum A geodetic datum (plural datums, not data) is a reference from which spatial measurements are made. In surveying and geodesy, a datum is a set of reference points on the earth's surface against which position measurements are made, and (often) an associated model of the shape of the earth to define a geographic coordinate system. Horizontal datums are used for describing a point on the earth's surface, in latitude and longitude or another coordinate system. Vertical datums measure elevations or depths. In engineering and drafting, a datum is a reference point, surface, or axis on an object against which measurements are made. WE-IT TUTORIALS (PH:8097071144/55)
map projections ? a method for representing part of the surface of the earth or a celestial sphere on a plane surface. WE-IT TUTORIALS (PH:8097071144/55)
Types of Map Projections WE-IT TUTORIALS (PH:8097071144/55)
Projected Coordinate System A Projected coordinate system (PCS) is a two-dimensional planar surface. However, the Earth's surface is three-dimensional. Transforming three-dimensional space onto a two-dimensional surface is called projection. WE-IT TUTORIALS (PH:8097071144/55)
State Plane Coordinate System State Plane Coordinate System (SPCS) is not a projection (also known as SPC, State Plane, and State). It is a coordinate system that divides the 50 states of the United States WE-IT TUTORIALS (PH:8097071144/55)
Public Land Survey System (PLSS) The Public Land Survey System (PLSS) is the surveying method used historically over the largest fraction of the United States to survey and spatially identify land parcels before designation of eventual ownership, particularly for rural, wild or undeveloped land. It is sometimes referred to as the rectangular survey system WE-IT TUTORIALS (PH:8097071144/55)
Vector Data Model ? Vector model Points, lines, polygons WE-IT TUTORIALS (PH:8097071144/55)
TIGER DATABASE Topologically Integrated Geographic Encoding and Referencing Topology in the TIGER database involves 0- cells or points. 1-cells or lines, and 2-cells or areas. Address ranges and ZIP codes in the TIGER database have the right- or left- side designation based on the direction of the street. WE-IT TUTORIALS (PH:8097071144/55)
Raster Data Model a raster is divided into rows, columns, and cells. Cells are also called pixels with images WE-IT TUTORIALS (PH:8097071144/55)
Why use Raster Overlay Analysis/Overlay Operations Arithmetic Operations Addition Subtraction Division Multiplication Logical (Boolean) Operations Where conditions occur or do not occur together AND, OR, NOT, GT, LT, etc. WE-IT TUTORIALS (PH:8097071144/55)
TYPES OF RASTER DATA Satellite Imagery Digital Elevation Models Non-USGS DEMs(plotting) Global DEMs(global scale) Digital Orthophotos Bi-Level Scanned Files(scanned image) WE-IT TUTORIALS (PH:8097071144/55)
Encoding types in Raster Cell by Cell Encoding Run-length Encoding Quad tree WE-IT TUTORIALS (PH:8097071144/55)
END OF UNIT 1 WE-IT TUTORIALS (PH:8097071144/55)