Land Surveying Units
Chains, Rods, and Modern Measurements
Learn Survey UnitsProperty deeds and land descriptions often use surveying terms like "chains," "rods," and "sections" that date back centuries. Understanding these units helps interpret property documents, understand land surveys, and convert between historical and modern area measurements.
Gunter's Chain System
Edmund Gunter invented the surveyor's chain in 1620, creating a system that elegantly links linear and area measurements:
| Unit | Feet | Meters | Relationship |
|---|---|---|---|
| Link | 0.66 | 0.201 | 1/100 chain |
| Rod (pole/perch) | 16.5 | 5.029 | 25 links = ¼ chain |
| Chain | 66 | 20.117 | 4 rods = 100 links |
| Furlong | 660 | 201.17 | 10 chains |
| Mile | 5,280 | 1,609 | 80 chains |
Area Units from the Chain System
| Unit | Square Feet | Square Meters | Acres |
|---|---|---|---|
| Square link | 0.4356 | 0.0405 | 0.00001 |
| Square rod | 272.25 | 25.29 | 0.00625 |
| Rood (¼ acre) | 10,890 | 1,012 | 0.25 |
| Square chain | 4,356 | 404.7 | 0.1 |
| Acre | 43,560 | 4,047 | 1 |
| Section | 27,878,400 | 2,590,000 | 640 |
The Acre Relationship
An acre was defined as 1 chain × 10 chains (66 ft × 660 ft = 43,560 sq ft). This made calculations simple: count square chains and divide by 10 to get acres.
US Public Land Survey System
The PLSS, established in 1785, divided public lands using a hierarchical system:
| Division | Size | Acres | Hectares |
|---|---|---|---|
| Township | 6 mi × 6 mi | 23,040 | 9,324 |
| Section | 1 mi × 1 mi | 640 | 259 |
| Half section | ½ mi × 1 mi | 320 | 130 |
| Quarter section | ½ mi × ½ mi | 160 | 65 |
| Quarter-quarter | ¼ mi × ¼ mi | 40 | 16 |
This system still defines property boundaries across most of the western United States.
Metes and Bounds
Older property descriptions (especially in the eastern US) use metes and bounds—directions and distances from reference points:
Common Terms
- Metes: Measurements (distances)
- Bounds: Boundaries (natural or artificial features)
- POB: Point of Beginning
- Thence: From that point
Example Description
"Beginning at the old oak tree on Miller Road, thence N 45° E 10 chains to a stone marker, thence S 45° E 15 chains to Smith Creek..."
Modern Survey Units
Metric System
Modern surveying increasingly uses metric units:
- Distances: Meters (m)
- Area: Square meters (m²) or hectares (ha)
- Coordinates: UTM or latitude/longitude
GPS and GIS
Modern surveying uses:
- GPS: Centimeter accuracy possible
- GIS: Geographic Information Systems for mapping
- Coordinates: Decimal degrees or UTM
Despite modern technology, legal descriptions often still reference historical units.
Converting Survey Units
| From | To Feet | To Meters | To Acres |
|---|---|---|---|
| 1 chain | 66 | 20.117 | — |
| 1 rod | 16.5 | 5.029 | — |
| 1 square chain | 4,356 sq ft | 404.7 sq m | 0.1 |
| 1 square rod | 272.25 sq ft | 25.29 sq m | 0.00625 |
| 1 rood | 10,890 sq ft | 1,012 sq m | 0.25 |
| 1 section | 27,878,400 sq ft | 2,590,000 sq m | 640 |
Conclusion
Land surveying uses a mix of historical and modern units. The chain-based system (where 10 square chains = 1 acre) underlies many property descriptions still in use. The US Public Land Survey System divides land into townships and sections. Understanding these units helps interpret property deeds, legal descriptions, and historical documents—even as GPS and metric units become more common.