LECTURE 6: OBJECT MODELING FOR TRANSPORTATION

1. GIS APPLICATIONS IN TRANSPORTATION

2. REPRESENTING THE NETWORK

3. ARCGIS NETWORK FEATURES

Among the earliest GIS applications

Chicago studies of the 1960s

data on journey to work from neighborhood to workplace

data on daily shopping, recreation trips

the origin-destination matrix

matrix as a class of objects

UML association class

attributes of pairs of features

migration table

distance matrix

turntable

spatially binary data

traffic analysis zones (TAZs)

collections of polygons

DIME and TIGER

1970 census

Dual Independent Map Encoding

blocks as polygons

street segments as arcs

intersections as nodes

2D perspective

every polygon bounded by arcs

every arc terminates in nodes

checks on consistency

1980 census

Topologically Integrated Geographic Encoding and Referencing

joint project of the Bureau of the Census and the US Geological Survey

1:24,000 in urban areas

1:100,000 in rural areas

stimulus to industry

Tomtom, Navteq

importance of accuracy

traps to protect copyright

examples 1 2 3

Google

Maps

Streetview

routing for pedestrians

indoor 3D routing?

open-source alternatives

volunteered content

OpenStreetMap

Google MapMaker

data acquisition

TIGER

air photos

GPS tracks

individuals

vans

Geocoding

translate street address into coordinates

TIGER has address ranges

Problem: find the latitude and longitude of 950 West Broadway, Columbia MO

     Here are some records from that database:

     12901900006711    A    Broadway    W    A40    600    698    601    699
     6520365203            292901901902502509300930    6    7    252    553
     9234550038951400    9234700038951600

     12901900006712    A    Broadway    W    A40    700    798    701    799
     6520365203            292901901902502509300930    6    7    253    554
     9234700038951600    9234890038951800

     12901900006713    A    Broadway    W    A40    800    898    801    899
     6520365203            292901901902502509300930    6    7    253    556
     9234890038951800    9235030038951900

     12901900006714    A    Broadway    W    A40    900    998    901    999
     6520365203            292901901902502509300930
     9235030038951900    9235270038952200

Procedure:

1. search the TIGER file for Boone County, MO for features with the name "West Broadway" or equivalent (W. Broadway, Broadway W. etc)

note problem with lack of standard name syntax

get about 30 matches for the length of W. Broadway

2. find the record that lists the address range which includes address 950:

record #6714 covers the block from Greenwood to West Blvd, and includes the following data:

longitude 92.3503 to 92.3527 - .0001 degrees longitude is about 9m on the ground - block is about 216m long

latitude 38.9519 to 38.9522

ZIP code 65203 on both sides

census tract 6 on the left side, 7 on the right

address ranges 900 to 998 on the left, 901 to 999 on the right

no shape points, so we assume the block is straight

3. determine the coordinates of number 950:

assume that the houses are evenly spaced along the street, and that the full range of addresses is used (this is not necessarily a good assumption, but it's the best that can be done without more information)

longitude is: 92.3503 + {(950-900) * (92.3527-92.3503) / (998- 900)} = 92.3515

latitude is: 38.9519 + {(950-900) * (38.9522-38.9519) / (998- 900)} = 38.9521

note that the results are given to the same precision as the block endpoints, that is, to about 10m

we could have calculated more digits, but they would have been meaningless given the accuracy of the inputs (the database was built from 1:24,000 mapping)

how to express TIGER in UML?

TIGER is good enough for geocoding

define an address locator in ArcCatalog with properties

using a shapefile with streets and address ranges

create a table of addresses

geocode in ArcCatalog or ArcMap

get summary results

interactive resolution of difficult cases

display results

TIGER is good enough for simple navigation

MapQuest site

Paul Revere's directions

Intelligent Transportation Systems

information services that help move traffic faster

911

routing emergency vehicles

maintaining inventories

signals, signage

pavement management

icing

mowing

evidence for lawsuits

coordinates and GPS

Onstar, police accident reporting

linear referencing

distance along route from landmark

120m west of Patterson on Hollister

mismatch of GPS and databases

How to represent the continuous network?

break it into discrete pieces

stretch of street between adjacent intersections

"links" "edges" "segments" "blocks"

State between Victoria and Sola

State is ~50 records rather than 1

opportunity for typing errors

what if a new intersection is added?

break an existing record into 2

what defines an intersection?

at grade?

laneways?

LPOLY, RPOLY?
FNODE, TNODE?
geometry

shape points

length
traffic direction
lane count
traffic density
obstruction?
slope

geometry
lights?
stop signs?
turn restrictions
traffic circle?
at grade?

what's missing?

intersection ID
from link to link
restrictions
radius

intersections

interrupted median dividers

traffic circles

complex intersections

bizarre street numbering

dealing with lanes

new ITS applications

Network

a view of infrastructure

transportation, utilities

water, gas, telephone, rail, road

a collection of edges and junctions

specialized features that connect

support network functions

tracing

shortest paths