The "vara castellana" is a historical unit of length that was used in Spain. It was commonly used for land measurement and other purposes in various regions of Spain, especially in the Castile region, which is why it is called the "castellana" vara. The exact length of the vara castellana could vary by region and historical period.
In general, the vara castellana was approximately 835.9 millimeters or about 32.91 inches in length. However, variations existed, and in different parts of Spain and at different times in history, the length of the vara castellana could differ slightly.
Like many historical units of measurement, the vara castellana has largely been replaced by more standardized and modern systems of measurement, such as the metric system. In contemporary Spain, the metric system is the standard for length measurement.
A chain is a unit of length used in some older systems of measurement, particularly in surveying and land measurement. In the United States, one chain is equal to 66 feet or 22 yards. Internationally, it's defined as exactly 20.1168 meters.
Chains were historically used for measuring large plots of land and for surveying purposes, often in agriculture and real estate. However, the use of the chain as a standard unit of measurement has largely been replaced by the more modern and standardized metric and imperial systems, which use units like meters, feet, and yards.
The term "chain" comes from the practice of physically measuring land using a chain made of linked metal bars or wire. Each chain was typically 66 feet long, and surveyors would lay out chains end to end to measure distances across large areas. Today, modern surveying equipment such as electronic distance measuring devices (EDMs) and GPS technology have largely replaced the use of physical chains in land surveying.