Introduction to GIS
Popular Mechanics, 1954
1986 $2,599 1 MB of RAM 2017, $750, 128 GB memory, 2 GB of RAM Computing power has increased exponentially over the past 30 years, Allowing the existence of GIS
What is a Geographic Information System? A computer-based information system that stores geographically referenced data, links it with nongraphic attributes (data in tables) allowing for a wide range of information processing including manipulation, analysis and modeling. A GIS also provides for map display and production. Information system organized system for the collection, organization, storage and communication of information. In GIS the data is: Spatial i.e., points, lines, polygons, rasters Temporal i.e., containing a time metric (e.g., sea surface temperature for Jan1, 2011) Create interactive queries (user-created searches) Spatial analysis Edit layered data in maps Enable map algebra and maths Present results
Common GIS Software ESRI ArcGIS Desktop industry standard GlobalMapper QGIS GIS not limited to the above - most modern programming languages and databases contain packages/syntax to work with spatial data Matlab R Python SQL Server MySQL Combining GIS + Programming: One key to quantitative versus qualitative science Will help get you a job!
Why learn GIS and computational skills?
ArcGIS editions ArcView Desktop: ArcView ArcEditor ArcInfo Standard Professional Enterprise ArcMap - the main mapping application which allows you to create maps, query attributes, analyze spatial relationships, and layout final projects. ArcCatalog - organizes spatial data contained on your computer and allows for you to search, preview, and add data to ArcMap as well as manage metadata and set up address locator services (geocoding). ArcToolbox - contains tools for geoprocessing, data conversion, coordinate systems, projections, and more. ArcEditor, ArcInfo used with databases ArcMap ArcCatalog ArcToolbox
GIS Layer Stack Marine Land Use
ArcGIS (and QGIS) Desktop File Types: ShapeFile (.shp) - a vector data storage format for storing the location, shape, and attributes of geographic features. A shapefile is stored in a set of related files (i.e.,.shp,.dbf,.sbn, etc.) and contains one feature class. Layer File(.lyr) - is a file that stores the path to a source dataset and other layer properties, including symbology. In comparison to a shapefile, a layer file is a just a link\reference to actual data, such as a shapefile, feature class, etc. It is not actual data because it does not store the data's attributes or geometry. A layer file primarily stores the symbology for a feature and other layer properties related to what is seen when the data is viewed in a GIS application. So, shape file is the georeferenced data, a layer stylizes the shape file.
ArcMap Interface Main Menu Toolbars Map Display Table of Contents Data Frame Page Layout
ArcMap Basic Navigation Full Extent Pan Fixed Zoom In/Out Zoom Out Previous/Next Extent Zoom In Zoom In Operate on Data Frame Operate on Layout Zoom Out Pan Zoom Whole Page Fixed Zoom In/Out Previous/Next Extent Zoom 100% ArcMap Querying Unselect Features Select Features Select Elements Go to X/Y Add Data Identify Measure Find
ArcMap Desktop Views: Data View: When you want to browse the geographic data on your map, choose data view. Data view is an all-purpose view for exploring, displaying, and querying the data on your map. This view hides all the map elements on the layout, such as titles, north arrows, and scale bars, and lets you focus on the data in a single data frame, for instance, editing or analysis. Layout View: In layout view, you'll see a virtual page on which you can place and arrange map elements, and you can do almost everything you can in data view, plus design your map.
a key concept (i.e., test material!)
Vector Representation of the world using points, lines, and polygons. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets. Raster A representation of the world as a surface divided into a regular grid of cells. Raster models are useful for storing data that varies continuously, as in an aerial photograph, a satellite image, a surface of chemical concentrations, or an elevation surface. Points (0 dimensional) Points as cells Lines (1 dimensional) Lines as a sequence of cells Polygon (2 dimensional) Polygon as a zone of cells
Geographic North Geographic North Pixels Raster Points, lines and polygons Vector Geographic East Geographic East
examples of. RASTER VECTOR Digital satellite remote-sensing images Digital aerial photographs Scanned maps or photographs Digital elevation models from topographic map contours GPS measurements Survey measurements Topographic maps Toponymy (placename) databases
Geographic North Raster s offer a poor representation of geographic dimensionality Columns 1,1 point (0 dimensional) line (1 dimensional) Rows area (2 dimensional) Geographic East In a raster, points, lines and areas are represented as quantized units of geographic area. Grid structures DO NOT allow precise location information
GIS Hierarchy and Databases
Layers of GIS Information Municipalities
Layers of GIS Information Census Tracts
Layers of GIS Information Lakes and Rivers
Layers of GIS Information Polluting Companies
Layers of GIS Information Schools
Maps and Databases are Interactive
Relational Databases Foundation for many Information Systems, including GIS Organizes data into one or more tables (or "relations") of columns and rows Rows are also called records, columns are fields, and cells are items A unique field (or combination of fields) identifies each row as is called a key (student ID in the below).
Relational Databases Rows have keys that are shared and these are called relationships and are used to create joins. Duplication of data is avoided and reuse is an underlying concept SQL (Structured Query Language) is the language for querying and maintaining the database GIS such as ArcGIS can connect to other databases that store data Animal detections + = Bathymetry Bathymetry at animal detection location
Relational Databases
Relational Databases
Spatial data
3 basic methods for representing a surface in GIS: DEM (digital elevation model): set of regularly spaced sampled ground points in the x and y dimensions (although spacing not necessarily the same in each) accompanied by an elevation measure (z dimension). The DEM terminology was introduced by USGS. Two concepts used for determining elevation at points within the grid cells: Lattice: each point represents a value on the surface only at the center of the grid cell (vector point) Surface grid considers each sample as a square/rectangular cell with a constant surface value (raster) TIN (Triangulated Irregular Network): a set of adjacent, non-overlapping triangles with x, y coordinates and z vertical elevations for their vertices, along with topological relationship between the triangles and their adjacent neighbors. Contour lines: lines of equal elevation, drawn at a given interval The general term digital terrain model (DTM) may be used to refer to any of the above surface representations when in digital form. DEM sometimes used synonymously with DTM and apply to ocean bathymetry. DEM can be used to represent SSHA, SAL, SST, Geostrophic currents, etc.
DEM (Digital Elevation Model) a sampled array of elevations (z) that are at regularly spaced intervals in the x and y directions. two approaches for determining the surface z value of a location between sample points. In a lattice, each mesh point represents a value on the surface only at the center of the grid cell. The z-value is approximated by interpolation between adjacent sample points; it does not imply an area of constant value. A surface grid considers each sample as a square cell with a constant surface value. Advantages Simple conceptual model Data cheap to obtain Easy to relate to other raster data Irregularly spaced set of points can be converted to regular spacing by interpolation Disadvantages Does not conform to variability of the terrain Linear features not well represented
Triangulated Irregular Network A set of adjacent, non-overlapping triangles computed from irregularly spaced points, with x, y horizontal coordinates and z vertical elevations. Advantages Can capture significant slope features (ridges, etc) Efficient since require few triangles in flat areas Easy for certain analyses: slope, aspect, volume Disadvantages Analysis involving comparison with other layers difficult
The topology of a TIN (source: after Zeiler 1999) Longley et al. 2005
TIN surface of Death Valley, California: wireframe showing all triangles shaded by elevation draped with satellite image Longley et al. 2005
Contour (isolines) Lines Contour lines, or isolines, of constant elevation at a specified interval, valley hilltop Advantages Familiar to many people Easy to obtain mental picture of surface Close lines = steep slope Uphill V = stream Downhill V or bulge = ridge Circle = hill top or basin Disadvantages Poor for computer representation: no formal digital model Must convert to raster or TIN for analysis Contour generation from point data requires sophisticated interpolation routines, often with specialized software such as ArcView Spatial Analyst extension ridge