Geographic information. Spatial referencing by coordinates

2003 ◽  
Keyword(s):  
Geographic Information ◽  
Spatial Referencing

Location Translation Within a Geographic Information System

1997 ◽  
Vol 1593 (1) ◽  
pp. 55-63 ◽  
Author(s):  
Wende A. O’Neill ◽  
Elizabeth Harper
Keyword(s):  
Information System ◽  
Geographic Information System ◽  
Urban Areas ◽  
Geographic Information ◽  
Translation System ◽  
Department Of Transportation ◽  
Additional Information ◽  
Surface Transportation ◽  
Spatial Referencing ◽  
Translation Systems

Location translation allows the use of multiple spatial referencing methods within a geographic information system (GIS). Most GIS users are familiar with planar or spherical coordinates expressed as (x, y) pairs of numbers whose values reflect the map projection used. Coordinates are characterized as unique physical locations on the earth’s surface. Transportation professionals have added many methods of referencing data that occur along lines. Linear referencing systems generally reflect a measure of distance from a known point. Common linear referencing methods are route–milepoint and route–reference post–offset. Street (postal) address systems also fall into the category of linear references. Linear referencing methods do not uniquely define locations on the earth’s surface without additional information about the location of the line (or road) on the earth’s surface. Although many of the off-the-shelf GIS systems allow conversion among a wide variety of planar or spherical referencing systems, few accommodate linear referencing systems, and none are capable of translating among linear referencing systems or between planar or spherical and linear systems. Some of the issues that arise in the development of location translation systems are discussed. A description of the data model and database requirements of the system designed for the Utah Department of Transportation is included. This location translation system was developed to facilitate crash reporting in urban areas, although there are numerous applications within transportation agencies.

Transit Path Calculation Supported by Special Geographic Information System-Transit Information System

1996 ◽  
Vol 1521 (1) ◽  
pp. 98-107
Author(s):  
Robert Chapleau ◽  
Bruno Allard ◽  
Martin Trepanier
Keyword(s):  
Information System ◽  
Geographic Information System ◽  
Optimal Path ◽  
Original System ◽  
Geographic Information ◽  
Transit Network ◽  
Pedestrian Network ◽  
Spatial Referencing ◽  
Impedance Functions ◽  
Path Calculation

The Société de Transport de la Communauté Urbaine de Montréal (STCUM; Montreal Urban Community Transit Corporation) has recently undertaken the task of computerizing its phone information center, called AUT-OBUS. AUT-OBUS provides callers with optimal route choices within the STCUM transit network. An original system based on geographic and operations data bases combined with interactive path calculation and data processing software has already been implemented. A special geographic information system was developed to process the origins and destinations on the basis of the client's specifications. Multiple forms of spatial referencing are provided: street addresses, trip generators and attractors, monuments, special activities, street intersections, transit references (subway and rail stations, bus routes, terminals, etc.). The best path calculation is carried out by using interactively calibrated impedance functions (walking, in-vehicle, waiting, transfers, fares, and mode restriction). An added challenge was the necessary consideration of the network geometry, commercial speed, day type, trip time, and headway and the validation of the computed paths with existing schedules. For a transit network the size of Montreal's, consisting of 16,000 bus stops, 230 bus routes, and a pedestrian network of 80,000 links and 28,000 nodes, the calculation of the optimal path for a given origin–destination pair is less than 2 sec with a typical personal computer with a Pentium processor.

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