Assigning Coordinate Levels to Non US Countries - trillium_discovery - trillium_quality - 17.2

Overview

Trillium creates lookup tables for latitude and longitude assignment using data from mapping suppliers. Trillium receives updates from suppliers every quarter, which helps ensure continuous improvement of the available data.

The level of supplier coverage varies as follows:

• From country to country: the supplier's data offerings are more advanced in some countries than others.
• Within each country: suppliers may have more detailed information in major cities and towns than in rural areas and smaller towns.

Geocode Coordinate Levels

The Geocoder returns coordinates at the following levels of accuracy relative to the input address:

Trillium always returns the most precise coordinate possible based on the available reference data from the supplier and the input addresses that you supply. A result code is generated that describes which type of coordinate has been returned.

There is a detailed information below about each level:

Interpolated Rooftop

Interpolated rooftop coordinates are linked to a specific, complete address using the house number, street name, city name, and any other relevant address components. The coordinates are calculated by Trillium using information retrieved from the supplier’s data.

Street Segments. The suppliers used by Trillium divide streets into one or more segments. Each segment generally describes a straight section of the street and varies in length depending on how straight the street is.

The definition of a street segment includes:

• Start and end coordinates
• The range of house numbers that the segment covers
• The side of the on which the street house numbers fall

Example. In the following map, the green highlighted street has three segments. The map shows the ranges of house numbers and the side of the street they occur.

The following process describes how the street segment definition is calculated:

Trillium calculates the coordinates for any house number on the street using the end points of the segment that contain the house number and the start and end coordinates. Using the position of the house number within the segment’s range, Trillium calculates how far from the start point the house number lies. (This assumes that all houses within the segment occupy the same amount of space.) This calculation produces a point on the street (the red icon on the map). Trillium offsets the position perpendicular to the line of the street segment on the correct side of the street to generate a realistic position for the building (the blue icon on the map). The size of the offset is determined by classification of the street, which is taken from the supplier’s data and indicates the type of street; for example, highway, major road, and so on.

Street Level

Street level coordinates are linked to a specific street using the street name, city, postcode, and any other relevant address components. The coordinates are taken directly from the supplier’s data, and are start coordinates of the first segment for that street in the data.

Postcode, City, and Region Centroids

These centroids are calculated by Trillium using the supplier’s data and are included in the Trillium latitude and longitude tables. They are calculated by averaging the coordinates of all of the addresses that fall in the postcode, city, or region.

Country Centroid

Country centroids are linked to the location of the country’s capital city.