geo_polygon_simplify()

Simplifies a polygon or a multipolygon by replacing nearly straight chains of short edges with a single long edge on Earth.

Syntax

geo_polygon_simplify(polygon, tolerance)

Parameters

Returns

Simplified polygon or a multipolygon in the GeoJSON format and of a dynamic data type, with no two vertices with distance less than tolerance. If either the polygon or tolerance is invalid, the query will produce a null result.

Polygon definition and constraints

dynamic({“type”: “Polygon”,“coordinates”: [ LinearRingShell, LinearRingHole_1, …, LinearRingHole_N ]})

dynamic({“type”: “MultiPolygon”,“coordinates”: [[ LinearRingShell, LinearRingHole_1, …, LinearRingHole_N ], …, [LinearRingShell, LinearRingHole_1, …, LinearRingHole_M]]})

• LinearRingShell is required and defined as a counterclockwise ordered array of coordinates [[lng_1,lat_1],…,[lng_i,lat_i],…,[lng_j,lat_j],…,[lng_1,lat_1]]. There can be only one shell.
• LinearRingHole is optional and defined as a clockwise ordered array of coordinates [[lng_1,lat_1],…,[lng_i,lat_i],…,[lng_j,lat_j],…,[lng_1,lat_1]]. There can be any number of interior rings and holes.
• LinearRing vertices must be distinct with at least three coordinates. The first coordinate must be equal to the last. At least four entries are required.
• Coordinates [longitude, latitude] must be valid. Longitude must be a real number in the range [-180, +180] and latitude must be a real number in the range [-90, +90].
• LinearRingShell encloses at most half of the sphere. LinearRing divides the sphere into two regions. The smaller of the two regions will be chosen.
• LinearRing edge length must be less than 180 degrees. The shortest edge between the two vertices will be chosen.
• LinearRings must not cross and must not share edges. LinearRings may share vertices.

Examples

The following example simplifies polygons by removing vertices that are within a 10-meter distance from each other.

let polygon = dynamic({"type":"Polygon","coordinates":[[[-73.94885122776031,40.79673476355657],[-73.94885927438736,40.79692258628347],[-73.94887939095497,40.79692055577034],[-73.9488673210144,40.79693476936093],[-73.94888743758202,40.79693476936093],[-73.9488834142685,40.796959135509105],[-73.94890084862709,40.79695304397289],[-73.94906312227248,40.79710736271788],[-73.94923612475395,40.7968708081794],[-73.94885122776031,40.79673476355657]]]});
print simplified = geo_polygon_simplify(polygon)

Output

The following example simplifies polygons and combines results into GeoJSON geometry collection.

Polygons
| project polygon = features.geometry
| project simplified = geo_polygon_simplify(polygon, 1000)
| summarize lst = make_list(simplified)
| project geojson = bag_pack("type", "Feature","geometry", bag_pack("type", "GeometryCollection", "geometries", lst), "properties", bag_pack("name", "polygons"))

Output

The following example simplifies polygons and unifies result

US_States
| project polygon = features.geometry
| project simplified = geo_polygon_simplify(polygon, 1000)
| summarize lst = make_list(simplified)
| project polygons = geo_union_polygons_array(lst)

Output

The following example returns True because of the invalid polygon.

let polygon = dynamic({"type":"Polygon","coordinates":[[[5,48],[5,48]]]});
print is_invalid_polygon = isnull(geo_polygon_simplify(polygon))

Output

The following example returns True because of the invalid tolerance.

let polygon = dynamic({"type":"Polygon","coordinates":[[[5,48],[0,50],[0,47],[4,47],[5,48]]]});
print is_invalid_polygon = isnull(geo_polygon_simplify(polygon, -0.1))

Output

The following example returns True because high tolerance causes polygon to disappear.

let polygon = dynamic({"type":"Polygon","coordinates":[[[5,48],[0,50],[0,47],[4,47],[5,48]]]});
print is_invalid_polygon = isnull(geo_polygon_simplify(polygon, 1000000))

Output