Browse Prior Art Database

Display Simplification by Elimination of Unnecessary Boundaries

IP.com Disclosure Number: IPCOM000081372D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 4 page(s) / 32K

Publishing Venue

IBM

Related People

Evey, RJ: AUTHOR [+2]

Abstract

Geographically-related data is most readily interpreted when it is presented in the form of a map. In many applications this map is composed of areas or "zones," such as Census tracts, police beats or traffic sectors.

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Display Simplification by Elimination of Unnecessary Boundaries

Geographically-related data is most readily interpreted when it is presented in the form of a map. In many applications this map is composed of areas or "zones," such as Census tracts, police beats or traffic sectors.

Described is an interactive system to facilitate the analysis and display of geographically-related data. Display is achieved using a graphical display terminal, such as the IBM 2250. To determine which of the map zones satisfy conditions of interest, PL/I-like statements are entered via the alphameric keyboard specifying the characteristics by which zones are to be sorted and identified. Each statement is given an alphameric symbol (not necessarily distinct), chosen by the user, to be displayed at the centroid of those zones satisfying the corresponding statement.

An interpreter translates the statements, searches the prescribed arrays to determine the zones satisfying one or more statements, and thus the appropriate symbol for each zone is determined. Display of these symbols at the zone centroids of the entire map unfortunately produces a very cluttered and distracting display, which obscures the pertinent information. To correct this problem, common boundaries between zones satisfying the same statements are eliminated.

The boundary elimination method is illustrated by a simplified example, using the map shown in Fig. 1. The boundaries of the five zones are stored by first creating an array of the (x,y) coordinates of the fourteen points numbered here P(14,2) (Table 1). Next another array L (Table 2) is formed starting with zone 1, and listing in the first column the sequence of points which compose the boundary of zone 1. In the example, this sequence is 1, 2, 5, 6, 4, 1. The second column consists of a list of the zones separated by the line segment to the point corresponding in the first column, beginning at the previous point in the first column. Thus, opposite 6 in the first column would be 4 since 5 precedes 6 in this column, and the segment 5-6 is part of the separation between zone 1 and
4.

Outside boundaries are given the number of the zone; thus, opposite 2 in the first column is 1, since segment 1-2 is an outside boundary of zone 1. To indicate to which zone the sequence of boundary points corresponds, the number of the zone is entered as the first element of the second column, with a minus sign used to indicate the start of a new zone boundary set. Thus for zone 1 the array has

1 -1

2 1

5 4

6 4

4 2

1 1. Completion of the description of the map given in Fig. 1 requires a two-column array of twenty-three elements, as shown in Table 2. This input data procedure results in the array L(23,2).

1

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To utilize the array in creation of a zone map with common boundaries suppressed between zones satisfying the same statement, an array of symbols, corresponding to the statement satisfied by each zone, is generated by the interpreter. Denote...