CensusMapDoc.tioga
Greene, July 18, 1989 7:04:19 pm PDT
Chauser, June 2, 1992 2:32 pm PDT
CensusMap
CEDAR 10.1 — FOR INTERNAL XEROX USE ONLY
CensusMap
Street and Address Locator
Dan Greene
© Copyright 1988 Xerox Corporation. All rights reserved.
Abstract: This package is a street and address locator for the US Census Bureau's GBF/Dime maps, using BiScrollers and QuadTrees to browse the maps and using the ApproxSymTabs to lookup street names. When data is available, the software will interpolate addresses on streets.
Created by: Greene.pa
Maintained by: Greene.pa
Keywords: Census Bureau, Street Maps, Locator
XEROX  Xerox Corporation
   Palo Alto Research Center
   3333 Coyote Hill Road
   Palo Alto, California 94304

For Internal Xerox Use Only
1. Introduction
This package uses census maps:

Geographic Base File/DIME (GBF/DIME), 1980 [machine-readable data file] / developed by local planning agencies in cooperation with the Bureau of the Census. --Washington: The Bureau [producer and distributor], 1980.
It builds search structures to support 2D browsing (a Quad tree) and approximate string matching, and displays the map using BiScrollers.
2. Getting Started
The browsing and matching software is on CedarChest:

% bringover -p /cedarchest7.0/top/CensusMap.df

The maps themselves are on Eich:

% bringover /eich-nfs/noir/greene/top/CMaps.df

To create a map browser and index use a command like

% CensusMap PaloAlto

Most of the Bay area has been divided into rectangular maps that are named after a central city, so you may have to use the name of a neighboring city to get the desired map. For example, Menlo Park would be on:

% CensusMap RedwoodCity

and Mountain View requires two maps:

% CensusMap PaloAlto Sunnyvale

The file CMapAliases will alias many of the local city names to an appropriate invocation of CensusMap.
2. Using the Map
The map are displayed using a Buttonless BiScroller which is documented in BiScrollersDoc.tioga. A summary of the commonly used commands are:

Fit. Centers entire map

Scale. Left click zooms in by a factor of 2, right click zooms out by a factor of 2.

Shift-lock down, left click in map. Move map location to center of viewer.

Shift-lock down, middle down. Two dimensional thumbing.
Unlike many paint procs, the map painter pauses every two seconds and checks the system load, so that YOU DO NOT NEED TO WAIT FOR PAINTING TO COMPLETE before using the other commands.
If you select (without the shift-lock down) a street/river/rail way on the map the name of the feature selected will appear in a small window to the right of the BiScroller buttons.
3. Using the Index
Location
You can misspell a substring of the street you are attempting to locate and the software will sequence through the nearest matches (in string edit distance). The edit distances have been weighted so that name prefix and suffix extension is light weight (an therefore a likely match). This makes it easy to omit street suffixes like "Avenue" and prefixes like "San," in fact all you really need to type is the most characteristic substring. Enter the misspelled substring after "Street Name:" and then punch "BestMatch" followed by as many "NextMatches" as are necessary to locate the right street. Once the street is located symbolically it can be located geographically by punching "ShowStreetOnMap." To locate an address on the street enter the number after "Address:" and then punch "ShowAddressOnStreet."
Street address locations are interpolated from data on the addresses at the ends of streets, so they are not always accurate, and in some industrial areas (where the Census Bureau has less interest) the address data is missing altogether. (For example, Coyote Hill, will match, but not 3333 Coyote Hill).
Map centering
Each time you punch one to the show buttons the software will use the button that is inverted to the right of "Selection Centering on Map" to determine how to repaint the map. If "Always" is inverted the map will always move to center a request, if "Never" is inverted the request will blink if it is on the screen, otherwise is will be invisible. Finally "If Necessary" centers an item only if part of it is off the screen.