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Technical

Polygon

The closed geometry defining parcel boundaries. Stored as GeoJSON, KML, or WKT; viewed in GIS software.

A polygon (Turkish: poligon or çokgen) is a vector data type in Geographic Information Systems (GIS) that defines a closed area. It must have at least 3 vertices, and the first and last points must coincide (closed shape). Every parcel, building footprint, zoning block, lake boundary is modelled as a polygon.

GIS has three fundamental vector geometry types: point — a single coordinate; line — connecting two or more points; polygon — a closed area. In real estate/zoning applications, parcel boundaries, building areas and zoning regions are all expressed as polygons.

Key polygon properties: area — in m² or hectares; perimeter — metre distance totalling vertex-to-vertex edges; vertex count. In GeoJSON, a polygon has the structure `"type": "Polygon", "coordinates": [[[x1,y1], [x2,y2], ..., [x1,y1]]]`. Libraries like PostGIS and Turf.js support polygon analyses (intersection, union, contains).

Polygons with holes (e.g. a public-use area inside private land) are modelled as MultiPolygon or Polygon with holes. On Drozero's map layers, parcel polygons are clickable; click opens block-parcel data.

Examples

  • 1.A 500 m² rectangular parcel is expressed as a 4-cornered polygon; in GeoJSON it has 5 coordinate points (the first point is repeated to close).
  • 2.In İstanbul's 1/1000 implementation zoning plan, every parcel is shown in a different colour polygon (housing yellow, green space green).
  • 3.After drone-collected land imagery produces an ortophoto, an engineer manually clicks corner points to draw the polygon; the system auto-calculates m².

Frequently Asked Questions

Is polygon the same as 'çokgen'?expand_more
Yes, technically identical — 'poligon' derives from English 'polygon', 'çokgen' is the pure Turkish equivalent. In GIS and surveying practice, 'poligon' is more common; mathematics prefers 'çokgen'.
How is polygon area calculated?expand_more
Given corner coordinates, the **Gauss (shoelace) formula**: area = |Σ(xᵢ × yᵢ₊₁ − xᵢ₊₁ × yᵢ)| / 2. In projected coordinates (metres), the result is directly in m²; in geographic coordinates (lat-lon), spherical geometry is required. PostGIS's ST_Area() handles this automatically.
Do overlapping polygons cause problems?expand_more
Yes. In the cadastre, overlapping parcel boundaries signal a **title dispute**; resolved in the cadastre court. In GIS, topological errors (overlaps, gaps) are detected and corrected with 'Topology Checker' tools in ArcGIS or QGIS. Drozero parcel maps come from TKGM; overlaps should be reported.
How many vertices should a polygon have?expand_more
Minimum 3 (triangle). Upper limit is technical; 100-1000 vertices is common in practice. Very detailed polygons (10,000+ vertices) add unnecessary detail and increase processing time — simplified with Douglas-Peucker algorithm. TKGM parcels typically have 10-30 vertices.

Related Terms

GIS (Geographic Information System)Block / Parcel (Ada / Parsel)OrthophotoCoordinate System

Sources

  • • OGC Simple Features Specification
  • • GeoJSON Format Specification (RFC 7946)
  • • TKGM Spatial Data Infrastructure Technical Documentation

Try the FAR/GCR calculator

Calculate total floor area, storey count and estimated unit count in seconds from parcel m² and zoning values.

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Last updated: 2026-04-24