How to solve the 180th meridian issue

The 180th meridian is the geographical boundary between the Eastern and Western hemispheres. It passes through the Pacific Ocean, Russia, Alaska, and Fiji.

The problem

When searching by location, the 180th meridian can lead to unexpected results. If a rectangle or polygon includes the 180th meridian, the search won’t include results from inside the area. Instead, the results return everything outside the area you selected.

The reason: longitudinal value reversal

When you cross the 180th meridian, the longitude switches from positive to negative numbers: from 180 to -180, not 181.

The solution: create two areas

If your area crosses the meridian, split the affected area into two adjacent shapes, one east of the meridian and one west.

Rectangles

Consider a rectangle that includes the 180th meridian: [70, 170, 60, -170]. To resolve the issue, split this rectangle into two smaller ones:

• Rectangle 1: [70, 170, 60, 180] (east of the meridian)
• Rectangle 2: [70, -180, 60, -170] (west of the meridian)

Use insideBoundingBox to define these shapes with the value [[70, 170, 60, 180], [70, -180, 60, -170]].

Polygons

Consider a polygon that includes the 180th meridian: [[70, 170], [80, 160], [90, 140], [80, 120], [70, 110], [60, 130], [70, 140]]. To resolve the issue, use insidePolygon to split this shape into two smaller ones:

• Polygon 1: [[70, 170], [80, 160], [90, 140], [80, 120], [70, 110], [60, 130], [70, 140]] (area east of the meridian)
• Polygon 2: [[60, 130], [70, 140], [70, 170], [60, 180], [50, 160], [60, 150], [60, 130]] (area west of the meridian)