Mapping Census Data in ArcView 3.x Nancy Lemay University of Ottawa Barbara Znamirowski Trent University
Workshop Outline Defining certain concepts and terms: Map scale, coordinate systems, datum and projections. We will try to understand these concepts
Workshop Outline (cont d) Understanding different file formats: -.e00,.shp,.shx,.dbf,.sbn and.sbx. Introduction to ArcView and its components. Hands-on exercise using census data and cartographic boundary files (CBF).
Map Scales A defined dimensional relationship between reality and the map (Robinson et al., 1995): a) Verbal: one cm represents ten kilometers b) Representative fraction: 1:10,000 c) Graphic scale: 5 0 0 0 0 5 0 0 0 1 0 0 0 0 M e t e r s d) Area scale: Represents square kilometers
Calculate Map Scales For example, if 2 cm on a map represents 1 km on the ground the scale would be 2 cm = 1 km, or... Scale is unitless because it is a ratio.
Examples small vs. large scale Large scale: 1:50,000 Small scale: 1:250,000
Coordinate systems A coordinate system is a reference system based on mathematical rules for specifying positions (locations) on the surface of the earth. The coordinate values can be spherical (latitude and longitude) or planar (such as Universal Transverse Mercator). A coordinate system is usually defined by a datum, ellipsoid and projection, and is specified in terms of units (e.g. degrees, meters).
Types of Coordinate Systems Geographic coordinate system: Uses latitude and longitude for locating positions on the uniformly curved surface of the earth. Rectangular/plane coordinate systems: Used to locate positions on a flat map. For example Universal Transverse Mercator (UTM)
Geographic Coordinate System The Equator (latitude) and Prime Meridian (longitude) are the reference points. Usually Greenwich, England is the Prime Meridian. The Cartographic Boundary Files, the Road Network Files and the representative points are disseminated in latitude/longitude coordinates. Prime meridian Equator
Decimal Degrees (DD) Decimal degrees are similar to degrees/ minutes/seconds (DMS) except that minutes and seconds are expressed as decimal values. Decimal degrees make digital storage of coordinates easier and computations faster. 60.34444 instead of 60º20'40"
Example: Converting DMS to DD degrees 60º20'40" minutes seconds 20 minutes.= 0.33333 (20/60) 40 seconds = 0.01111 (40/3600) Add up the degrees to get an answer: 60º + 0.33333 + 0.01111=60.34444 DD
Ellipsoid (Spheroid) and Geoid Ellipsoid - used as a reference of the earth s surface for the mathematical model of the earth. Mathematical approximation of the geoid. Geoid - estimates the earth s surface using mean sea level of the ocean with all continents removed.
Datum Geodetic reference system that specifies the size and shape of the earth. Base point from which the latitude and longitude of all other points on the earth's surface are referenced. Two types of datums: (1) Earth-centered (WGS84, NAD83), (2) Local (NAD27, ED50). The spatial data disseminated for the 2001 Census are based on the North American Datum of 1983 (NAD83). http://www.geod.nrcan.gc.ca/index_e/geodesy_e/reference04_e.html
Map Projections Process of transforming and representing positions on the earth's three-dimensional curved surface to a twodimensional (flat) surface. The process is accomplished by a direct geometric projection or by a mathematically derived transformation. Use projected spatial data to calculate distance!! For more information: http://mac.usgs.gov/mac/isb/pubs/mapprojections/projections.html
Map Projections Examples Cylindrical Equal Area Lambert Conformal Conic Preferred for world maps. Mollweide s Good for directional and shape relations along large east-west mid-latitudes. Good for middle latitudes.
Different File Formats Shapefile.shp is used in ArcView and ArcGIS and is accompanied by the following auxiliary files:.dbf the dbase file that stores the attribute information of features. Required..shx the file that stores the index of the feature geometry..sbn &.sbx the files that store the spatial index of the features..prj - the file that stores the coordinate system information..xml - metadata for ArcInfo 8.0, for using shapefiles on the Internet. Coverages are often published in a compacted form with the extension.e00 : Proprietary file format used to distribute Arc/Info datasets. Topology and attributes are properly maintained in this format.
ArcView Project File The ArcView.apr file contains the project information. Features are stored: view properties theme information layout information other types of information are stored. Return to the project without having to re-load all the associated files.
StatCan Spatial File Naming Convention First Character: projection of file: g if projection is Geographic Latitude/Longitude and l if projection is Lambert Conic Conformal. Next three characters: primary geographic boundary of file, for example csd. For example: gcsd035b02a_e.exe
Next three Numbers: geographic code of coverage, for example 035. Next character: file type (based on 1996 codes). a if digital boundary file (for Dissemination Warehouse only) (DBF in 1996) b if Cartographic Boundary File, detailed coverage for large-scale mapping c if detailed interior lakes hydrographic coverage e Ecumene r Road Network Files (RNF and SRNF) For example: gcsd035b02a_e.exe
Following two numbers: dissemination year (date stamp for versioning) The choices are: 01 if disseminated in 2001, 02 if disseminated in 2002, 03 if disseminated in 2003 etc. Next character: file format: a ARC/INFO ArcGIS Export File (e00), m MapInfo Export File (mid & mif) Final two characters: language _e English _f français For example: gcsd035b02a_e.exe
Introduction to ArcView 3.x
Tool bar Menu bar Button bar Project window Document windows Status bar
View display, query & analyze themes ArcView Documents Layout integrate documents to create presentationquality maps Table display attribute data Script program written in Avenue used to customize the interface, automate common functions or create applications
ArcView Projects Views Tables Charts Layouts Project window Displays the names of all project documents & acts as a gateway to all documents in the project. Scripts
Views and Themes Theme: A GIS links sets of features and their attributes and manages them together in units called themes. Each theme has a title and a legend in the view s Table of Contents. Themes
You can control visibility and change display order (by dragging) When a theme is turned on, ArcView draws it in the map display area. Theme Operations Active themes are raised To make more than one theme active, hold down the Shift key as you click on each theme. To invoke the Legend Editor Double-click on active theme.
Symbol Window Legend Editor Fill Palette Pen Palette Marker Palette Font Palette Color Palette Palette manager
Let s Map 2001 Census Data Proportion of Italian Mother Tongue by Census Tracts N 20 0 20 40 Kilometers Streets Hydrography Italian Mother Tongue Normalized by Total Population 0-0.005 0.005-0.014 0.014-0.031 0.031-0.075 0.075-0.146 Source: Statistics Canada 2001 Census data and cartographic boundary files Author: Nancy Lemay Projection: Lambert Conformal Conic
Saving the Beyond 20/20 table Open the B20/20 table «.ivt» for: Profile of Citizenship, Immigration, Birthplace, Generation Status, Ethnic Origin, Visible Minorities and Aboriginal Peoples, for Census Metropolitan Areas, Tracted Census Agglomerations and Census Tracts, 2001 Census - Cat. No. 95F0489XCB01005 After subsetting the B20/20 table to include only Ottawa Census Tracts, save the table as a «.dbf» file.
Importing the CBF.e00 file a) Under Start then Programs, you will find under Esri:
Importing the.e00 file (cont d) b) Click on Browse to find your.e00 file on your hard drive. c) Click on Browse and select where you want to save the new data files and type a new filename in Output Data Source.
Open ArcView Open ArcView and double-click on Views in the project view.
Set working directory When starting a project in which new data needs to be created, the working directory has to be set so that ArcView knows where to store the files. File -> Set Working Directory After this has been selected a dialog will appear where the working directory can be set.
Load cartographic boundary file To add a new theme click on
Make the theme active Add a check to make the theme active
Add table to your new project Open ArcView 3.x make Tables active in the project window, click on Add. (1) (2) (3)
Information on Table Joins A join function is provided in ArcView so that the census data can be appended to the attribute table of the CBF. In order to join the two tables, a common field containing the same values must be identified. Please note that the name of the field does not have to be the same, but the values in the field must be of the same type (string vs number).
Prepare census table for a join To Edit the census table click under Table > Start Editing Under Edit click Add Field Type «CTUID» for Name, select «String» as a Type and «10» for Width. Click under Table > Stop Editing
We need to convert these census tract labels to recreate the common field in our profile data. Click Calculate in the Field menu. The calculation is based on the following instruction: CTUID=505.AsString+[Geography].Left(7), which means that the CTUID string is created by adding the Ottawa CMA code as a string to the left-most 7 characters in each of the Geography labels.
Open CBF table To open the CBF table go back to the View and click the table icon on the button bar
Find the common field, it should be left justified (string). Identify common field
Join the census data with CBF Source table Destination table
In the attribute table click on the field you will use to join. You know the field is selected when it is sunken and darker than the surrounding fields. In the shapefile table click on the same field. Click Table in the menu and then Join or click on the following button: Destination table Source table
Calculate the ratio Open the destination table and under Table select Start Editing
Add a new field to calculate ratio Once the table is in edit mode, select Add Field under Edit.
Define the new field Give the new field a proper name. Select Number as Type. Type 4 for number of Decimal Places.
Calculate the new variable Under Field select Calculate Let s calculate the ratio of people who have Italian as a mother tongue and the total population.
Map the new variable Go back to the View and double-click on the active theme. We will select Graduated Color as a Legend type.
Select a classification field Select your newly created variable called Ratio for the Classification Field. Click Apply.
Choose a projection A projection is needed for publication purposes and for calculating distances. Under View select Properties. Select kilometers as Map Units and Distance Units. Click on Custom and select Lambert Conformal Conic.
Optional: add hydrography Click on the to add the hydrography shapefile. Remember to make it active by adding a checkmark. Double-click on the active theme to activate the Legend Editor and doubleclick on the the color box below Symbol. Click on the paint brush to select a new color. Click Apply.
Final results
Comparing ArcView 3.x and ArcGIS 8.x Same basic functionality as 3.x Separate software modules for organizing files (ArcCatalog), accessing tools (ArcToolbox) and working with data (ArcMap). Projection-on-the-fly Direct read of more data formats Can import 3.x project files and legend files
Terminology Project files (*.apr) become map documents (*.mxd) Projects become maps Views become data frames
Interface No more project window Table of contents Display view Source view Map display Toolbars
Importing Simple to do, but it has been known to cause problems. Primarily, cannot import all 3.x views Import 3.x project files (*.apr) Import 3.x legend files (*.avl)
Project file problem ArcMap allows the storing of relative path names. Use Set Data Source to find lost layers or simply remove and re-add the lost layer.
New terminology http://www.esri.com/news/arcuser/0402/files/talking.pdf
References Robinson, A.H., et al., Elements of cartography. 6th ed. 1995, New York: John Wiley. 674.
Partial Credits for Stolen Slides http://tdr.tug-libraries.on.ca/helps/gishelp.htm http://prod.library.utoronto.ca:8090/maplib/arcmap_guide.pdf http://www.ideal.forestry.ubc.ca/cons340/lecture03.pdf http://maps.nrcan.gc.ca/maps101/scale.html http://www.uottawa.ca/academic/arts/geographie/lpcweb/w eb2320/
More info on making your projects portable: http://www.wlu.ca/~wwwgeog/special/geomatics/pdf/tra nsportable.pdf http://www.esri.com/industries/k- 12/download/docs/transapr.pdf Importing ArcView GIS Projects into ArcGIS http://www.esri.com/news/arcuser/0701/avconvert.html