Methods of Geocoding: By Street Address, by Postal Code, or by Boundary (Especially for GATE-Geospatial 2022)

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Geocoding is the process of converting addresses (like a street address) into geographic coordinates (like latitude and longitude) , which you can use to place markers on a map, or position the map. Reverse geocoding is the process of converting geographic coordinates into a human-readable address.

What is Geocoding? Definition and FAQs|OmniSci

To geocode data, it must contain information about location such as a street address, a postal code, or a name of an area, e. g. country, census subdivision etc. Geocoding is about adding x, y coordinates to point locations represented by these pieces of information.

Methods of Geocoding

Three main methods of geocoding are available:

Diagram Shows Three Methods of Geocoding

Various ways of geocoding pinpoint records on a map with different levels of accuracy. The most accurate of these three methods is geocoding based on a street address.

Geocoding by Street Address

Address geocoding involves matching addresses in a table to be geocoded to the street names and address ranges in the street network file.

Geocoding software reads the first record in the file. It first matches the street name in both - table to be geocoded and a reference table, which is accompanied by a map. Once the street name is matched, all address ranges for this street are examined in order to determine the street segment where the particular address is found, on the odd or even number side of the street. This part of the geocoding process is known as address matching.

Table 1: Table to be Geocoded

Table of Content to be Geocoded by Street Address

Table 2: Sample Records from the Attribute Table for a Reference Layer

Table Shows the Attribute Table for a Reference Layer

Figure Shows Illustration of Street Address Geocoding Using the Street Network File as a Reference Layer

Image Shows Street Address Geocoding Using Street Network Fi …

Geocoding by Postal Code

Any database that includes postal code information can be geocoded by postal code based on a file that consists of postal code centroid points with the geographic coordinates attached to them.

Geocoding using postal code involves matching postal code information in the table to be geocoded to the postal code information (FSALDU - Forward Sortation Area Local Delivery Unit) in the PCCF file that acts as a reference layer.

Table to be Geocoded

Table Shows Geocoding by Postal Code

Sample Records and Fields from the Postal Code Conversion File

Table Content of Records and Fields from the Postal Code Con …

Based on the match (relational join operation) the table to be geocoded receives coordinates from the PCCF file and points can then be created on a map. The geocoded records will have locations identical to the centroid locations of those postal codes to which they were matched.

Geocoding by Boundary

Geocoding by boundary is the least accurate of the three methods of mapping point locations. Any boundary file, such as countries or Forward Sortation Areas, can be used, as long as the boundary name in the table to be geocoded can be matched with the boundary name in the reference table.

Table Shows Geocoding by Boundary
Table Content Shows Records and Fields from the Forward Sort …

Table shows sample records and fields from the Forward Sortation Area reference table.

Geocoding using FSAs produces inaccurate results in both urban and rural areas. The larger FSA, the less accurate of the results. But still, the map produced with this method is better than no map at all.

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