Q: Can I create .BNA boundary files using digitized boundary information (latitude and longitude values)?
A: You can enter coordinate information manually using the Boundary File Editor in TAP, or you can create your own boundary files following the format described below.
The SoftWright plotting programs provide the capability of adding boundary information to plots generated with the Terrain Analysis Package (TAP) Ô system. This information can include political boundaries (counties, cities, etc.), functional boundaries (business district, target market areas, etc.), roads, site locations, etc.
The boundary line data files are ASCII files that are compatible with other software that recognizes the Atlas BNA format, such as Golden Software's MapViewerÔ and SURFERÔ programs, as well as Caliper's Maptitude.
Boundary line files for each state, including counties, roads and zip codes, are available from SoftWright. TAP includes an editor to conveniently edit the .BNA objects, as well as other programs for filtering and selecting boundaries from the TAP Graphic Window.
Boundary line files can contain three types of objects:
Areas are three or more line segments that begin and end at the same point to form a closed figure. Areas can be used to represent any closed boundary, such as a county or city limits.
Lines are two or more line segments that do not begin and end at the same point and do not form a closed area. Lines can be used to represent roads, rivers, etc.
Points are single locations that can be used to locate transmitter sites, buildings, etc.
All boundary information in the file is represented by latitude/longitude pairs that define the end points of line segments (for lines and areas) or single point locations.
Boundary File Format
The boundary file information is saved in ASCII files using the same file format as described in Appendix C of the MapViewer manual from Golden Software. The file format is:
"Pname 1","Sname 1",type/length
"Pname 2","Sname 2",type/length
Pname is the primary name identifier for the object, enclosed in '"' marks. This Primary ID is typically a numerical identifier corresponding to the Federal Information Processing Standards (FIPS) code (if one exists) for the object. (Each state and county is assigned a unique identifier code in the FIPS system.) In other software (such as MapViewer) the Primary ID, such as the FIPS code, can be used to link boundary information to other data base items, such as population or other demographic data.
Sname is the secondary name identifier for the object, enclosed in '"' marks. This Secondary ID is typically the name of the object, such as a county name. The Secondary ID is used in TAP to write the name of the object on a plot.
Type/length is the identifier that indicates the type of object (point, line, area) and the number of latitude/longitude pairs used to represent the object in the file.
A positive integer greater than 2 indicates an area. The value indicates the number of coordinate pairs to follow. The last and first coordinate pairs should be the same to ensure a closed area.
A negative integer less than -1 indicates a curve (or line). The absolute value defines the number of coordinate pairs to follow.
The integer 1 indicates a point. Only one coordinate pair is allowed.
Coordinate values are indicated by decimal degrees of latitude and longitude. West longitudes and south latitudes are negative numbers to maintain normal plotting conventions (x values increase going right [east] and y value increase going up [north]).
Complex areas can include "islands." The coordinate pairs representing the islands are separated from each other by repeating the initial coordinate of the main area. The following sample file illustrates a complex area:
2,2 --begin main area
2,2 --end of main area
4,4 --begin island #1
4,4 --end island #1
2,2 --end main area
7,7 --begin island #2
7,7 --end of island #2
2,2 --end of main area
Boundary line files can be created and edited with an ASCII editor, or, more conveniently, with the TAP Boundary Line Editor program in the Boundaries menu.
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