Introduction to Geographic Information Systems

Transcription

1 Introduction to Geographic Information Systems The Environmental And Remote TecHnologies Lab MacMillan Hall, Room Outline Environmental and Remote TecHnologies Lab What is GIS GIS software the ESRI Suite Software demonstration The basics of spatial data files Categories File formats Finding spatial data files

2 Environmental And Remote TecHnologies Lab aka EARTH Lab Room 105 MacMillan Hall Dedicated to GIS and Remote Sensing Ten workstations / Server Large format plotter Large format digitizing board 2 Small format printers GPS Open schedule What Is A Geographic Information System A combination of computer hardware and software that allows for the utilization, creation and analysis of digital data files that are location based ie. Spatial. A GIS is unique because it is: Interdisciplinary Natural Sciences Engineering Social Sciences Health Depiction and Modeling Solving Real World Problems Dynamic

3 Vendors of GIS Software Products Caliper Corporation Maptitude Manifold Manifold System 5.00 Clark Labs Idrisi Autodesk Autodesk Map 2004 Google Maps / Earth Microsoft Live Local Intergraph Geomedia Environmental Systems Research Institute - ArcGIS GIS Software Suite by ESRI ArcIMS ArcGIS Server ArcExplorer ArcPad MapObjects ArcReader ArcView ArcGIS Desktop

4 ArcGIS Desktop 9.2 Software Two Interdependent Graphical Interfaces ArcCatalog the file manager ArcMap the viewing environment ArcToolBox a suite of tools designed to process spatial data (located inside ArcCatalog and ArcMap) Three Tiers ArcView 9.2 ArcEditor 9.2 Arc/Info 9.2 $$$ $$$$$$ $$$$$$$$$$ Demonstration Using GIS to Delineate Watersheds

5 Spatial Data File Basics 1) Not your average.doc document a) Complex architecture b) location is embedded c) Attribute data in a relational database is linked 2) Digital Representations of Features / Events a) surface, subsurface, atmosphere b) natural or man-made b) earth or other planetary bodies 3) Collectively Referenced by many generic names a) Geospatial Data, Geographic Data, GIS Data, Layers, Themes 4) Spatial Data Files fall into 1 of 2 possible types a) Vector b) Raster Vector Spatial Data

6 Vector Spatial Data Geographic Features as Points Example Layers Monitoring Stations Stream Outlets Bridges Dams Stormwater Discharges Vector Spatial Data Geographic Features as Lines Example Layers Streams Roads Canals Pipes / Conduits

7 Vector Spatial Data Geographic Features as Polygons / aka Polylines Example Layers Watersheds Lakes Wetlands Soils Land Use Vector Spatial Data Attributes

8 Vector Spatial Data Geographic Representation & Attributes are linked Every Record has a corresponding Feature Vector Spatial Data Advantages Spatial context Measurements Coincidence Queries

9 Raster Spatial Data Features are represented by a continuous surface Each pixel has a numeric value Text values possible infrequent Pixel values may be actual measurements color values (0 255) thematic representations Each pixel encompasses a square unit of surface area Some pixels can be coded as No Data Raster Spatial Data Pixel Values represent actual measurements of Elevation

10 Raster Spatial Data Pixel Values are used to assign gray scale or true color values Raster Spatial Data Pixel Values are used to represent categories

11 Raster Spatial Data Advantage = Performance of Mathematical Operations Spatial Data File Formats 1. Coverage Vector based Supports representation of geographic features as points, lines, or polygons Relational database (holding attributes) is Info software that predates windows operating system Complex structure on the disk (two folders and a multitude of files) Topology 2. Shapefile Vector based Supports representation of geographic features as points, lines, or polygons Relational database (holding attributes) is dbase Structure is less complex on the disk, but still confusing at first No topology (unless converted from a coverage)

12 Spatial Data File Formats 3. Grid Raster based Values can be integers, floating point Complex structure on the disk (two folders and a multitude of files) 4. Image files Raster based.jpg.tif.sid.bmp.png Structure is less complex on the disk Orthophotographs / Georeferencing 5. Geodatabase Superseding coverages, shapefiles, grids, images A container one file on disk holds everything Coverages and shapefiles become feature classes Grids and Images become rasters Two types: personal and multi-user Personal = Microsoft Access Multi-user = Oracle, SQL Server, IBM DB2; Informix Coordinate Systems Where am I? Where are you? Where is the lake/stream/ monitoring station? How do I get there? What is the distance?

13 Coordinate Systems Two Categories 1) Geographic 2) Projected Geographic Coordinate Systems Properties Earth maintained as a sphere Datum (sphere measured differently) Latitude and Longitude define locations Latitude = North or South of Equator = Y Longitude = East or West of Prime Meridian = X Units = degrees, minutes, seconds (decimal degrees)

14 Geographic Coordinate Systems Geographic Coordinate Systems Available in ArcGIS

15 The Downfall of Geographic Coordinate Systems While longitude and latitude can locate exact positions on the surface of the globe, they are not uniform units of measure 1 degree of longitude ranges from 0 to 111 km You can t measure distances or areas accurately or display the data easily on a flat map or computer screen Square Degrees? Properties Projected Coordinate Systems Earth NOT maintained as a sphere a Projection is applied to flatten it Datum (sphere measured differently) X is a position along the horizontal plane from an origin Y is a position along the vertical plane from an origin X & Y become a coordinate pair Units = meters or feet Projection = mathematical equations which translate locations on a spherical surface to a twodimensional plane

16 Projected Coordinate Systems The mathematical equations (the projection ) which translate locations on a spherical surface to a two-dimensional plane fall into one of three categories: Planar Projections Conic Projections Cylindrical Projections Projected Coordinate Systems

17 Projected Coordinate Systems Available in ArcGIS The Downfall of Projected Coordinate Systems Distortion of Geographic Features

18 Spatial Data Files and Coordinate Systems in ArcGIS Desktop 1) In a research project, you probably will obtain spatial data files that are undefined or have different coordinate systems Conversion Errors with certain tools/procedures Warning messages Data files that don t line up 2) ArcMap does not like it when the coordinate system of a spatial data file has not been explicity Defined the *.prj file Where to find spatial data files Federal Agencies NOAA EPA USGS FDA FEMA CDC State GIS Programs MassGIS RIGIS Municipalities or Counties (not so much in RI) Academic Institutions EARTH Lab Server Private Data Developers (expensive)

19 Demonstration Georeferencing