GIS: GEOCODING AND DYNAMIC SEGMENTATION chp 16

Applications of Dynamic Segmentation (data application-4)

1. Data management: speed limits, rest areas, bridges, pavement conditions, stream reach data, etc • Different routes can be created in the same linear feature (transit) • Different events can reference the same route (environmental data: base flow height, temperature, mean width, for the same route (stream)). 2. Data Display: Once an event table is linked to a route, table is georeferenced and can be used as a feature layer. 3. Data Query: perform both attribute data query and spatial data query on an event table and its associated event layer. 4. Data Analysis. Between individual event layers or two.

Variations of Geocoding (6)

1. Intersection matching 2. Zip code geocoding 3. Parcel level geocoding 4. Reverse geocoding 5. Place name alias geocoding 6. Photo geocoding

Dynamic segmentation (3)

1. locates spatial features from a data source often lacking x and y coordinates. 2. Works with linearly referenced data such as traffic accidents. 3. Designed to bring together a projected coordinate system with a linear referencing system (two fundamentally different measuring systems)

Geocoding (3)

1. the process of plotting street addresses or intersection points on a map. 2. conversion of x and y data 3. Geo-referencing satellite images.

Common geocoding approaches

Address geocoding (address matching)

Applications of Dynamic Segmentation

By converting linearly referenced data stored in a tabular report into events and routes, D.S can display, query, and analyze the data in a GIS environment.

Dynamic segmentation

Dynamic segmentation allows for events to be plotted on a route through a linear measurement system

Business Applications

Geocoding is most used in matching zipcode of customers and prospects to the census data. Parcel geocoding can link parcel IDs to parcel boundaries and allow property/insurance companies to use info to determine insurance rate based on distance of parcel to areas prone to flood. Also site and market area analysis

Applications of Geocoding

Great tool for wireless emergency services, crime mapping and analysis, and public health monitoring

Quality of Geocoding

It is exclusively expressed by the match rate and positional accuracy. The latter is measured by how close each geocoded point is to the true location of the address

Preprocessing

Parsing breaks down addresses to components (number, name, type, state, zip, etc). Results allow for matching of these components. Standardization identifies places and each address component in order.

Reference Database

TIGER/Line files, extracts of geographic/cartographic information from the U.S. census Bureau's MAF Tiger database. These are legal and statistical area boundaries

Photo geocoding

attaches location information to photographs

Reverse geocoding

converts point locations into descriptive addresses

Line events

cover portions of a route (pavement conditions). A line event table must have route ID, and from-to measures.

Matching

done against a reference geodatabase. Mismatches can occur* (misspelling, incorrect address, abbreviation unrecognized, outdated database, etc). In order to decrease mismatching, minimum candidate score and the minimum match score is used. Lower match scores can yield more matches, but also more geocoding errors

Route

linear feature with a linear measurement stored in its geometry. It has x, y coordinates PLUS and m value. The M value is the linear measurement. This value can be interpolated from milepost or other reference markers

Event

linearly referenced data (speed limits, traffic accidents, habitat conditions on a stream, etc) Events are stored in an event table. Events may be POINT OR LINE EVENTS.

Intersection matching: (corner matching)

match address data with street intersections on a map. Geocoding engine finds the location of the point where the two streets intersect. (police collision reports*)

Place name alias geocoding

matches a place name with a street address

Zip code geocoding

matching a zipcode to the code's centroid location. • It is NOT street level geocoding • Uses reference database containing x-y coordinates, either geographic or projected, of zip code centroids as opposed to a street network

Parcel level geocoding

matching parcel number to parcel centroid location, if parcel database available, plots parcel boundaries

Creating event tables (2 methods)

o Event table from an existing table, with data on IDs and linear measures through milepost river mile, and other data. o Event table by locating point or polygon features along a route. Similar to a vector-based overlay operation.

Creating Routes (6)

o The interactive method allows for selecting existing lines from a layer that make up a route and apply a measuring command to the route selected. o Data conversion method: creates routes at once from all linear features or from features selected by data query. o Simple route: one direction, no loops or branches o Combined Route: joined with another route o Split Route: route subdivides into two routes o Looping Route: route intersects itself.

Point events

occur at point locations: (top sings) to locate these events, a point event table must have route ID, location measures, and attributes describing the event.

Plotting

once matched, we plot as a point feature. Geocoding engine first locates the street segment in the reference database. THIS PROCESS IS LINEAR INTERPOLATION.

Location-Based services

refers to any service or app that extends spatial information processing to end users via the internet or wireless network.

Address matching process (3)

uses a geocoding engine, involves: preprocessing , matching and plotting

Wireless emergency services

uses built-in GPS receiver to locate a mobile phone user in need of emergency dispatch service.

LINEAR INTERPOLATION

• Offsetting plotting options: Side offset and end offset are options that allow geocoded plotting of point features away from its interpolated location along a stream segment. • Side offset: places a geocoded point at a specific distance from the side of street segment. (point-in-polygon overlay). • End offset: point feature at a distance from the end point of a street segment, preventing it from falling on top of a street