SHAPELY_SIMPLIFY
Simplifies an input WKT geometry using the Douglas–Peucker algorithm with a user-specified tolerance.
The tolerance controls maximum allowed geometric displacement; larger values usually reduce vertex count more aggressively.
Informally, the simplified geometry G' satisfies a bounded deviation from G under the chosen tolerance \varepsilon.
This implementation preserves topology to reduce invalid geometry artifacts during simplification.
Excel Usage
=SHAPELY_SIMPLIFY(geometry, tolerance)geometry(str, required): Input geometry (WKT).tolerance(float, required): All points in the simplified object will be within the tolerance distance of the original geometry.
Returns (dict): Excel Entity representing the simplified geometry.
Example 1: Simplify a line
Inputs:
| geometry | tolerance |
|---|---|
| LINESTRING (0 0, 1 0.1, 2 0) | 0.2 |
Excel formula:
=SHAPELY_SIMPLIFY("LINESTRING (0 0, 1 0.1, 2 0)", 0.2)Expected output:
{"type":"String","basicValue":"LINESTRING (0 0, 2 0)","properties":{"WKT":{"type":"String","basicValue":"LINESTRING (0 0, 2 0)"}}}
Example 2: Simplify a polyline
Inputs:
| geometry | tolerance |
|---|---|
| LINESTRING (0 0, 1 0.2, 2 0.1, 3 0) | 0.15 |
Excel formula:
=SHAPELY_SIMPLIFY("LINESTRING (0 0, 1 0.2, 2 0.1, 3 0)", 0.15)Expected output:
{"type":"String","basicValue":"LINESTRING (0 0, 1 0.2, 3 0)","properties":{"WKT":{"type":"String","basicValue":"LINESTRING (0 0, 1 0.2, 3 0)"}}}
Example 3: Simplify a polygon
Inputs:
| geometry | tolerance |
|---|---|
| POLYGON ((0 0, 2 0, 2 1, 1.2 1.2, 2 2, 0 2, 0 0)) | 0.3 |
Excel formula:
=SHAPELY_SIMPLIFY("POLYGON ((0 0, 2 0, 2 1, 1.2 1.2, 2 2, 0 2, 0 0))", 0.3)Expected output:
{"type":"String","basicValue":"POLYGON ((0 0, 2 0, 2 1, 1.2 1.2, 2 2, 0 2, 0 0))","properties":{"WKT":{"type":"String","basicValue":"POLYGON ((0 0, 2 0, 2 1, 1.2 1.2, 2 2, 0 2, 0 0))"}}}
Example 4: Simplify a multipoint geometry
Inputs:
| geometry | tolerance |
|---|---|
| MULTIPOINT (0 0, 1 1, 2 2) | 0.5 |
Excel formula:
=SHAPELY_SIMPLIFY("MULTIPOINT (0 0, 1 1, 2 2)", 0.5)Expected output:
{"type":"String","basicValue":"MULTIPOINT ((0 0), (1 1), (2 2))","properties":{"WKT":{"type":"String","basicValue":"MULTIPOINT ((0 0), (1 1), (2 2))"}}}
Python Code
from shapely import wkt
def shapely_simplify(geometry, tolerance):
"""
Returns a simplified representation of the geometric object.
See: https://shapely.readthedocs.io/en/stable/reference/shapely.simplify.html
This example function is provided as-is without any representation of accuracy.
Args:
geometry (str): Input geometry (WKT).
tolerance (float): All points in the simplified object will be within the tolerance distance of the original geometry.
Returns:
dict: Excel Entity representing the simplified geometry.
"""
try:
if not geometry:
return "Error: Geometry required"
geom = wkt.loads(geometry)
simplified = geom.simplify(tolerance, preserve_topology=True)
wkt_str = simplified.wkt
return {
"type": "String",
"basicValue": wkt_str,
"properties": {
"WKT": {"type": "String", "basicValue": wkt_str}
}
}
except Exception as e:
return f"Error: {str(e)}"