Topic 8: Geocoding and Dynamic Segmentation

Question 1

1. Methods for geocoding addresses
   - Address matching, and variants

Answer 1

Address matching requires:
- geocoding engine - a third-party service or engine built into a GIS, such as ArcGIS’s Address Locator
- input data - addresses, typically that must be parsed prior to analysis
- geocoding reference database - eg., DMTI’s CanMap Address Points or Postal Code Suite

Question 2

Where to get data for geo-referencing and Address Parsing?

Answer 2

Address information is broken down into fields or elements that make up the full street address

Question 3

ArcGIS location reference databases?

Answer 3

Called locators or locator services in ArcGIS

Question 4

Why may some addresses be slightly off?

Answer 4

linear interpolation is used to estimate location

Question 5

Variations on address matching?

Answer 5

• Zip or postal code matching - locate a region or centroid of the region defined by code
• parcel-level geocoding - locate by cadastral parcels
• place name geocoding - matches a place to a geographic location
• reverse geocoding - converts point locations to descriptions

Question 6

1. Methods for geocoding addresses
   - Intersection matching

Answer 6

• represents another variant of address matching

Question 7

2. Route-based location references
   - Linear referencing

Answer 7

• linear referencing: georeferencing along the distance of a line feature

Question 8

What is the measure value or M-value?

Answer 8

Used in linear referencing, can be used to identify point locations or attributes along route

Question 9

Why use linear referencing?

Answer 9

• Record events along a route by measuring the distance
• Associate multiple sets of attributes to line features without requiring the underlying lines to be segmented in the database

Question 10

2. Route-based location references
   - Routes, events, and dynamic segmentation

Answer 10

• Routes: linear features that have distance embedded in the dataset
• 2 types of events: point events (eg., auto collisions, construction sites) and line events (eg., winter road conditions, road construction zones, road surface conditions)
• By combining a route with an event table, we can create a new layer of information by dynamically segmenting the data into new attributes

Question 11

Benefits of dynamic segmentation?

Answer 11

• requires only a small amount of information to create
• can generate unlimited layers per route
• routes and events are independent, so one route is shared to all associated event layers (easier editing and updates)

Question 12

Limitations to dynamic segmentation?

Answer 12

• Specifying point features that are not coincident with the route is error-prone (eg., campgrounds just off the highway)
• requires calibration of distance data and measured values stored in the route
• editing the alignment of a linear feature will modify the m-values, requiring re-calibration