Georeferencing , Geocoding, andNetwork Analysis

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Georeferencing

How do we make sure all our data layers line up ?

Georeferencing:= linking a layer or dataset with spatial coordinates

Registration:= lining up layers with each other

Rectification: The process by which the geometry of an image is made planimetric 2

Georeferencing Based on Data Types

• Raster and Raster

• Vector and Vector

• Raster and Vector

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GeocodingConcepts and Definitions

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• What is Geocoding • Geocoding is a process of creating map features from

addresses, place names, or similar textual information based on attributes associated with a referenced geographic database, typically a street network that has address ranges associated with each street segment or 'link' running from one intersection to the next.

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Data Collection Methods

• Two main methods:

– Direct Collection Approach

– Matching Approach

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Direct Collection Approach

• Digitizing from available topographic maps • Direct collection using field techniques (ex.GPS)

Areas, Street, Dwelling

Global Positioning System (GPS)Digitizing from a topographic map

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Matching approach• Using an Address locator database and street

network database in a GIS • Joining an address database to an existing

spatial database for the area of interest

First Avenue

Second Avenue

Right of Street

Left of Street

#1 #99

#2 #100

address number

Main StreetFirst Avenue

Right of Street

Left of Street

#1 #99

#2 #100

#51

#32

Nodes

Second Avenue

Street SegmentStreet Network

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Some Example of Geocoding applications

• 911 emergency response• Map Quest and Google Earth• Finding locations of customers• Marketing analysis• Mapping distribution of crimes• Mapping township/range descriptions

Network Analysis

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What is a network?1) Any system of interconnected linear features.

What is a network?

2) A system of linear features connected at intersections and interchanges. These intersections and interchanges are called nodes. The linear feature connecting any given pair of nodes is called an arc.

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Networks

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• Using Network Analyst, you can find thepath that will reach specified locations inthe most efficient order. The path can be theshortest path or the fastest path. NetworkAnalyst also gives you the option to returnto the point of origin when defining a path.

• Network Analyst provides you with directionsfor navigating a route. The directions can becustomized to include different units, such astime or distance, or landmarks to help you findyour way while navigating the route.

1) Find the optimal path What it can do?

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• Accessibility is a measure, usually in units of distanceor time, of how easy it is to get to a location orlocations.

• For example, 12,350 people may be able to drive tothe hospital emergency room within 12 minutes;

• 2,125 potential customers may live within a 1.5kilometer (walking) distance of a shopping center;and a fire truck can reach 3,000 homes andbusinesses within 7.5 minutes.

• The simplest way to model accessibility is to use astraight-line distance or radius that extends outwardfrom a specific location.

• While this may be useful if you're in an airplane or aboat, it doesn't reflect the way people move from onelocation to another on land.

2) Modeling accessibility

What it can do?

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3) Finding the Best Route• Finds the route that minimizes travel cost through a series of stops • Options

• Cost Attribute (kms, minutes, etc)• Find best order• Time windows• Cost on stops• Directions

What it can do?

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4) Finding the Closest Facility

Finds the routes that minimizes travel cost between incidents and multiple facilities

Options• Cost Attribute• Number of facilities to

find• Cut-off value• Direction of travel• Costs on incidents and

facilities• Directions

What it can do?

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5) Finding Service Areas

Find the area or lines that can be traversed within a specified cost

• Create polygons around specified locations

• Create service area lines

Options•Cost Attribute•Multiple Break values•Direction of travel•Polygon generation options•Line generation options

What it can do?

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6) More Network Analysis Options• Other parameters include

• Barriers• U-Turn policy• Restrictions• Exact route vs.

Hierarchical route

Exact route Hierarchical route(major roads)

What it can do?

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7) Finding an Origin-Destination Cost Matrix

Generates an “OD” matrix of the cost from each originlocation to each destinationlocation.

Options• Cost Attribute• Cut-off value• Number of destinations to find

What it can do?

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Networks

Best route

Closest facilityService areasVehicle routingLocation-allocation

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Thank You

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