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This 47 page Class Notes was uploaded by Sierra on Friday March 4, 2016. The Class Notes belongs to FNR 210 at Purdue University taught by Ningning N. Kong in Spring 2016. Since its upload, it has received 19 views. For similar materials see Natural Resource Information Management in Agriculture and Forestry at Purdue University.
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Date Created: 03/04/16
Data Models and Georeference 1 Map .mxd file Document Data Frame Layer Feature 2 Basic component of a layer Linked to one row in attribute table Has a location, shape, and a symbol 3 Three types of GIS features: Point feature: A point feature represents a single location. It defines a map object too small to show as a line or area feature. A special symbol or label usually depicts a point location. Line feature: A line feature is a set of connected, ordered coordinates representing the linear shape of a map object that may be too narrow to display as an area, such as a road, or a feature with no width, such as a contour line. Polygon feature: An polygon feature is a closed feature whose boundary encloses a homogenous area, such as a state, county, or census block. 4 Two data models are commonly used in GIS: Vector & Raster Organization 1 Point ID X Y Points 2 4 1 32.7 45.6 3 2 76.3 19.5 3 22.7 15.8 etc….. 1 6 C Line Begin End Lines A B ID Point Point 239 A 6 9 9 B 9 1 C 239 1 etc….. 12 13 Polygon 11 52 22 ID Lines Polygons A 11, 12, 52, 53, 53 54 41 B 52, 53, 9, 41, 54 9 22, 13 6 Points - ◦ Marker or point symbol, ◦ color, ◦ size and angle. Lines – ◦ Line symbol, ◦ color, ◦ width Polygon – ◦ Fill color and pattern, ◦ Outline width and color, ◦ background color 7 Not using attributes Using Attributes 8 Names (city, county, buildings) – LABEL Types and conditions ◦ Landuse (forest, water, urban, cropland) How would you symbolize this? ◦ Ranking (1-5) of scenic view along a highway How would you symbolize this? 9 Usually requires grouping the data for display using graduated colors or size or both How many classes (groups) do you need? How do you divide the data into groups? 10 Turn on the labels for your layer – Based on attribute value Parameters: ◦ Size ◦ Font ◦ Color ◦ Position 11 Shapefile Coverage Geodatabase Arc/In(coverage format) Versions 1-7 form 1980 -1999 Arc Macro Language (AML) ArcGI(geodatabase format) Versions 8.1-10.3 2000- Visual Basic Application ArcView(shapefile format) Versions 1-3 form 1994 -1999 Avenue script language 12 Coverage 13 Shapefile: includes a set of files with the same file name but different extensions. These files have to be saved in the same folder. An ESRI shapefile consists of three or more files (with extensions .shp, .shx, .dbf, .sbx and .sbn) 3 mandatory files: Main File (geography) <filename>.shp Database File (attributes) <filename>.dbf Index File (indexing) <filename>.shx 14 Geodatabase A collection of geographic datasets of various types held in a common place (database). 3 Types of geodatabase Personal GDB File GDB Enterprise GDB Microsoft Folder of Storage Format Access binary files DBMS Storage capacity 2 GB 1 TB Depends on per table* edition Supported OS Depends on Windows Any platform edition platform Single editor Single editor Multiple editors Number of users Multiple readers Multiple readers & readers Extend the Geodatabase level Dataset level transaction model Editing lock with Versions 15 Inside a Geodatabase 16 Two data models are commonly used in GIS: Vector & Raster Elevation and Satellite imageries are two common raster data sources. Raster image resolution: cell dimension Pros: Conceptually simple & efficient Well established processing and analysis algorithms Cons: Rigid data structure Linear features are not well represented 18 The Storage Space/Resolution Tradeoff Decreasing the Cell Size by one-half causes a Four-fold increase in the storage space required 19 20 Vegetation Classification Map Discrete data – unique value Digital Elevation Model Continuous data – Stretch or classify 21 Geodatabase Raster dataset ArcInfo GRID TIFF Many other formats 22 23 In ArcMap, you have two options to work with your map: ◦ Data View ◦ Layout View Analysis: Data View Map Production: Layout View 24 Title North Arrow Legend Scale bar/text Other text Neatline 25 In ArcMap, a map document is saved as a *.mxd file. A MXD file saves information about: ◦ Reference to different map layers ◦ Symbology, labels, map layout, etc. A MXD file doesn’t save information of the layers themselves. 26 27 Where in this world are you? 28 How do we locate a point on the earth? The most basic system is the spherical grid ◦ longitude (measures east- west), Meridians ◦ latitude (measures north - south), Parallels ◦ measured in degrees (DMS or DD) ◦ 3-D perspective 29 What is the shape and size of the earth? Complex Simple Earth’sActual Shape mathematical mathematical estimation of the estimation of earth’s shape earth’s shape 30 There are locally “best fit” ellipsoids geoid Ellipsoid B Ellipsoid A 31 Datum - Defines the surface (ex radius for a sphere, major axis and minor axis or inverse flattening for an ellipsoid) and the position of the surface relative to the center of the earth. There maybe infinite reference surfaces. Nations or governing bodies can agree on points and surfaces as standard references. 32 Commonly Used: North American Datum of 1927 (NAD 27) NAD 83 World Geodetic System 84 (WGS 84) We can transform positions from one datum to another via mathematical operations. http://www.fs.fed.us/r1/fireinfo/tools/lat_long_&_datums_dicussion.doc 33 Geographic Projected Copyright © 2004–2008 ESRI. All rights reserved.al Locations 34 Project a 3-D earth to a 2-D map. ◦ Linear units are most common ◦ 2-D perspective ◦ There are always projection errors. 35 A systematic rendering of locations on a 3-D spherical coordinate system (lat./long.) to a two- dimensional system. Distortion introduced by projection: ◦ Shape ◦ Area ◦ Distance ◦ Direction 36 Simple - tangent to the globe at a point, parallel, or meridian, or Secant - passing through the earth (multiple standard lines. Standard line – line(s) (point) of tangency between the projection and the reference globe. ◦ No distortion at standard line. ◦ Distortion increases with distance from the standard line. 37 38 At national level: Transverse Mercator Lambert Conformal Conic Albers Equal-Area Conic Equidistant Conic 39 At state level: State Plane Coordinate (SPC) Universal Transverse Mercator (UTM) Public Land Survey System (PLSS) ◦ Special Case –Historical ◦ Legally important – Deeds/ownership descriptions ◦ Is NOT a ‘projected’ coordinate System and cannot be Projected or Defined 40 41 42 Used in most of the Central and Western US Established for inventory and transfer of property Grid system ◦ 6 square mile Sections within ◦ Subdivide into 36 1-mile square sections ◦ Quarter, quarter-quarter sections 43 Define T ownship 44 45 SE1/4, SE1/4, NE1/4, sec. 13, T2S., R2W. 46 Used in many of the Eastern and Southeastern States. Also used for land titles and transactions. Example: "beginning with a corner at the intersection of two stone walls near an apple tree on the north side of Muddy Creek road one mile above the junction of Muddy and Indian Creeks, north for 150 rods to the end of the stone wall bordering the road, then northwest along a line to a large standing rock on the corner of the property now or formerly belonging to John Smith, thence west 150 rods to the corner of a barn near a large oak tree, thence south to Muddy Creek road, thence down the side of the creek road to the starting point." 47