A square chain is a unit of area measurement that is now considered obsolete and not commonly used. It was historically used in some English-speaking countries, including the United States and the United Kingdom, as part of the older system of land measurement.
One square chain is equal to an area of 10 square rods, or 484 square yards. In terms of square meters, one square chain is approximately equal to 404.68564224 square meters (m²).
The square chain was often used in land surveys and property descriptions in the past, but it has been largely replaced by the more standardized metric and imperial systems of measurement. In modern times, square meters and square feet are the more commonly used units for measuring land area.
A hectare (ha) is a unit of area commonly used in many countries, especially in agriculture and land management. It is equal to 10,000 square meters (m²) or 0.01 square kilometers (km²). The term "hectare" is often used to describe the size of large land areas, such as agricultural fields, parks, and estates.
To provide some perspective, a hectare is approximately the size of a square field with sides that are 100 meters (about 328 feet) long. It's a convenient unit for measuring land area in situations where using square meters or square kilometers would result in very large or small numbers.