Factors in Zoned Geographic Grid

[KathiSchleidt]

The Zoned Geographic Grid provides different factors in dependency on latitude, in order to avoid issues caused by meridian convergence at high latitudes. For each latitudinal zone, a specific longitude spacing for the cells of the geographic grid (equal or greater than the latitude spacing) is provided as follows:

• Zone 1 Lat[0°–50°] Factor: 1
• Zone 2 Lat[50°–70°] Factor: 2
• Zone 3 Lat[70°–75°] Factor: 3
• Zone 4 Lat[75°–80°] Factor: 4
• Zone 5 Lat[80°–90°] Factor: 6

As most of territories in continental European are included in Zones 1 and 2 (Cape North in Norway is approximately at 71° latitude), we focus on these 2.

Within Zone 1, the same offset should be used for both Latitude and Longitude components.

Within Zone 2, the offset for Longitude must be double the offset for Latitude.

[KathiSchleidt]

Unclear is if countries that span 50°Lat (e.g., DE, FR) must provide 2 separate coverage objects, one above and one below, or if one Zone can be selected to provide data in a consistent manner for the entire country.

[KathiSchleidt]

Here a simple example of a Zoned Grid for NL using a very course 1° grid.

The basic grid (not yet taking the zone factors into account) is as follows:

After applying the factor for Zone 2, the Zoned Grid is shown below in green: