CREATE LOCALIZER Statement

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CREATE LOCALIZER

Some data providers do not include region data for each feature, instead region polygons are provided. The CREATE LOCALIZER statement is used to build a region description from the provided polygons. Using the localize function, this information may then be used to populate the L_REGION and R_REGION properties of a street.

Syntax

Alchemy

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CREATE LOCALIZER [NESTED] name ON col_list FROM file_list;

Note
The NESTED keyword indicates that a strict region hierarchy is present. That is, each subregion belongs in precisely one region.

Nomenclature

name	The name given to this localizer. This name will be used to identify the localizer when using the localize function
col_list	A list of columns containing the names of each region
file_list	A list of files containing the respective region geometry

Example

First we would create a nested localizer using the CREATE LOCALIZER statement:

Alchemy

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CREATE LOCALIZER NESTED "myRegions"
  ON (%sbrb_name, %town_name, %cnty_name)
  FROM ("path_to\suburbs", "path_to\towns", "path_to\counties");

We would then use the localize function to populate the region fields of the street:

Alchemy

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IMPORT STREETS {
        $regnames = localize("myRegions", %geom);
}
[
        ...
        L_REGION 1 = $regnames[0],
        R_REGION 1 = $regnames[1],
        L_REGION 2 = $regnames[2],
        R_REGION 2 = $regnames[3],
        ...
]
FROM "path_to\street_data";

Caution
The region types must be ordered most specific first when working with a localizer. In this example the suburb (smallest and most specific region type) is specified first, followed by the town and then the county. A smaller region number indicates a more specific region.