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Add Shapes Operation Census Tract Demographics Geodemographics WebCourse |
Mapping Your Locations & Areas with CommunityViewer -- adding and viewing points and polygons This section provides an overview of how the CommunityViewer software can be used to add your own points/markers and polygons/areas to a map. The map in the following view shows a thematic map of median household income by census tract for the Tulsa, Oklahoma area. Tracts are shaded by colors for median household income as shown for the data value intervals in the legend panel (at left). At the same time, the three additional layers, created using the CV Add Shapes tool, are shown. 
• tulsasites.shp is a set of points representing prospective sites an investor is evaluating • Terrority 1 is a polygon area -- a custom defined market study area • tulsacompsites.shp is a set of points representing competitor locations Application Objective. In this example, an investor seeks to examine 4 locations that are available for a new store. Three competitor locations are known to exist. The investor also seeks to examine a specific market area. To facilitate the market analysis, a next step is to develop shapefiles that can be used to represent these points and area. Other geography and data can then be added to a project for analysis of an even broader set of data. Add Shapes Operation. Start CV and open the project to be used. Invoke the AddShapes operation using Tools>AddShape. Three options are available: • Add Points & Polygon -- used to create both a points shapefile and polygon shapefile. • Add Points -- used to create only a points shapefile. • Add Polygon -- used to create only a polygon shapefile. When the Add Point & Polygon option is selected, points are clicked onto the map. Each point becomes a vertex forming the polygon also being created. A dbl-click signals end of the process, closing the polygon. As the process is completed, a points shapefile and polygon shapefile are created. The Add Point(s) option may be used to add one or more points. If one point is to be created, a single dbl-click creates the single point shapefile. The Add Polygon option is used to create only a polygon. In CV2, many polygons may be created; whereas in CV1 there is only polygon created per polygon shapefile. Multiple shapefiles may be created to view multiple areas at the same time. As the operations start, a prompt appears for the name of the shapefile to be created. The file name selected must not be in use. It will be created by the process. The previous point added may be undone by clicking the right mouse button. A message then appears 'Start adding points. Dbl-click to close polygon'. The message varies some by type of operation. The process is ended with a dbl-click (on the last point) and a message such as 'New marker shapefile created.' appears. The shapefile(s) are added to the project. Modifying Shape Attributes. The following shape attributes (shapefile dbf fields) are created for points and polygons created: name (char 20), code (char 2), n9 (numeric 9), and c20 (char 10). For polygon, a prompt appears when creating the polygon for the name and the code fields. For points, the name field is automatically assigned as 'P'+sequence number of the point being created. Other field values remain null. Modify the point or polygon shapefile dbf using the Database>dBrowser operation. The following graphic shows the c:\cv1\mapfiles\tulsacompsites.dbf open for processing: 
To change a record/field value click in the cell and key in the new value. Clicking in any other cell following the change automatically updates the file permanently. There is no save operation on this form as the save operations are automatic. goto top |
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