Lab 10 Geocoding

Lab 10 Geocoding - 44:005 Foundations of GIS Lab 10:...

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44:005 Foundations of GIS Lab 10: Geocoding Overview of the exercise… Use the Find tool to geocode a single street address Geocode a list of street addresses Obtain GIS layers from the ArcIMS map service Geocoding Geocoding involves combining tabular data (such as a table full of addresses) with spatial data (such as a shapefile full of road segments) to assign geographic locations to the tabular data. + = Geocoding assigns a geographic identifier (such as lat/long or UTM coordinates) to each record in the table. You can also geocode media (as Flickr does with photographs). Once assigned geographic coordinates, the features can then be mapped and entered into geographic information systems. Address matching Address matching (or address interpolation) is one method for geocoding. This method makes use of data from a road layer where each road segment has already been assigned geographic coordinates. Each road segment is attributed with an address range (house numbers at either end of the segment). Geocoding takes an address, matches it to a road and specific segment (such as a city block) and interpolates the position of the address, within the range along the segment. For example, the address 10 Main Street will be placed halfway along a road segment whose address ranges from 2 to 20 Main Street. The address matching algorithm finds an address based on certain assumptions. Typical assumptions, and those used in this lab, are that the even numbers fall on the right side of the road, odd numbers fall on the left side of the road and addresses are evenly spaced along the road. 044:005 Lab 10 pg. 1 of 15
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In this exercise, we will match some addresses from Iowa City. The roads in any road network may be difficult to address match because naming conventions are not standard. The use of street names such as Gen Degaulle Dr and St. Bernard Ave. makes the use of a geocoding algorithm difficult. You may find that the use of directional prefixes (such as N., W., E., and S.) and odd arrangements of house numbers also causes problems. The steps of the algorithm used by ArcMap are summarized below: ArcGIS Desktop Help 044:005 Lab 10 pg. 2 of 15
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I. Geocode a Single Address Using the Find Tool 1. Copy the lab 10 data to your student folder. 2. Add the ‘Johnson_County_Centerlines.shp’ layer to a new ArcMap document. This file contains a line representation of all the road segments in Johnson County. 3. Open up the attribute table of the Johnson_County_Centerlines layer so you can see the attributes you have to work with. Right-click the layer name and select Open Attribute Table . Each row of the attribute table represents a different road segment. As you can see reading across the column headers, the attribute table includes information about the name of the road, the type of road surface and the zip code on each side of the road among other things. The attributes FROMLEFT, TOLEFT, FROMRIGHT and TORIGHT specify the lowest and highest addresses along each road segment. For example, the addresses in the first road segment run from 300 to 324 Morningside
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This note was uploaded on 04/01/2012 for the course 044 005 taught by Professor Davidbennett during the Fall '11 term at University of Iowa.

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Lab 10 Geocoding - 44:005 Foundations of GIS Lab 10:...

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