NR 422: GIS Review Jim Graham Fall 2010

What is GIS? Geographic Information System? Geographic Information Science? A system that provides the ability to work with information that is referenced to the surface of the earth. Is a paper map a GIS?

What is GIS (con’d)? A GIS contains at least: –A Computer –A Software Application (ArcGIS) –Some Spatial Data –A User And works together to perform some geospatial function

What can GIS do? Make a map Find directions to known location Find local a Star Bucks Determine cost of roads, developments Predict the extent of an invasive species Map ancient civilizations Help manage natural resources!

What can’t GIS do? Guess the directions you want to take Be 100% up to date Be 100% accurate

Steps in GIS 1.Acquiring data 2.Preparing data 3.Assembling data (making electronic maps) 4.Analysis 5.Preparing final documents (inc. Cartography) 6.Distribution

GIS Process Software - Preparation - Assembly - Analysis - Cartography Spatial Data Maps Analysis Results InputOutputManagement & Analysis

Preparation Decompression (unzip) File Format Conversion Projection and Datum Conversion Data Organization

Georeferenced Layers

Cartographic Elements Minimal elements of a map: –Title –One or more views of spatial data –Legend –Scale bar –Credits: Author and data sources –Projection and Datum –North Arrow Common elements: –Regional/Location map

Layers and Attributes Layer names with attributes: –Cities: name, population –States: name, area –Parks: name, type –Plots: name, species –Trees: species, DBH Each city, state, park, plot or tree is a feature

Types of Data “Discrete” Vector “Drawings” –Points –Polylines –Polygons “Continuous” Raster “Photos” –Grids ESRI ArcMap Data Set GoogleMaps

Cities (when at large extents) Camping Sites Starbucks! Fire stations Trees Houses Wells Mines Points X1,Y1 X2,Y2 X3,Y3

Polyline (Network) Streams Roads Pipelines V1 (X1,Y1) V2 (X2,Y2) V3 (X3,Y3) V5 (X5,Y5) V4 (X4,Y4) L1 L2 L3 L4

Polygons Lakes Political regions: Nations, States/Provinces, Counties Parks, Refuges, Forests EcoRegions Watersheds Oil Fields V1 (X1,Y1) V2 (X2,Y2) V3 (X3,Y3) V4 (X4,Y4) E3 E1 E2 E4

Shapes A Shape is one or more points, polylines, or polygons that make up a geographic feature: –Stream network –Road network –Group of Islands –A park –A nation –A state –A county –A city

Features A single geographic element that can have attributes attached to it: –River: Poudre River –Road: I-25 –Islands: Hawaiian Islands –Park: Rocky Mountain National Park –Nation: United States –State: Colorado –County: Larimer –City: Fort Collins

Vector Features (Shapes) Points Polylines Polygons

Topology Wyoming Colorado

Wyoming Non-topological V1 V2 V4 V3 V1 V2 V3 V4

Vector Data Storage Options ESRI / ArcMap Options: –Shapefiles –GeoDatabases –Coverages GoogleEarth: –KML There are many others!

Shapefile Most common throughout the GIS world NOT Topological! Files: –“shp” – spatial data (coordinates) –“dbf” – attributes (dBase file) –“prj” – projection (includes datum) –etc.

Coverage Was common –Being replaced by Geodatabases? Is topological Contains files and folder

Rasters (Digital Photos)

Zoomed In

Pixelation

Raster = Matrix of Pixels

Geo-Referenced Raster Known Projection and Datum (X1,Y1) (X2,Y2) (X4,Y4) (X3,Y3)

Types of Rasters Aerial and Satellite Photos: Brightness DEM: Elevation (meters) –Slope: -90 to +90 –Aspect: 0 to 360 degrees –Hill shade: Brightness based on sun angle and slope Topos: Brightness (RGB) Indexes: Land Cover Type Spatial Analysis: Varies

Geo-Referenced Raster File Formats ESRI: Grids GeoTIFF ENVI: IMG NASA: HDR Many others!

Summary Vector data: –Points, Polylines, Polygons –Shapes and features –Topology –ESRI File Formats: Shapefiles, Coverages, GeoDatabases Raster data: –Grids of rows, columns, cells –Cells contain pixels –Pixels can have one or more samples –ESRI File Format: Grid –Types: Photos, DEMs, Topos, Land Cover Type

Where are we? If you’re at: –Coordinate: , –Where are you? Can’t tell without a system to “reference” the coordinates to the earth, we are lost!

Coordinate Reference Systems Units: –Degrees, Feet, Meters, Miles, Kilometers Coordinate System –Cartesian or Rectangular –Spherical Projection –Geographic or Un-projected –UTM –State Plane Datums: –NAD27, NAD83, WGS84, HARN

Coordinate Reference Systems Bottom Line: –The projection, datum, and units must be defined for data to be referenced together –The projection, datum, and units must be the same for detailed analysis For now: –Make sure each of your files has a projection and datum defined!

Finding the Reference System All of these are reference systems: –ArcCatalog: –ArcMap Layer Properties: –ArcMap Toolbox: “Projection” –“prj” file If it’s not there: –Check the metadata (xml file) –Check the web site –Contact the provider!

Defining the Reference System ArcGIS Toolbox: –Define Projection Not –Project!