Stadiametric rangefinding, or the stadia method, is used to quickly measure distances with an engineer's transit, theodolites, or auto-level and a graduated rod (Please note that most Total Stations do not have stadia markings). The instrument must be used on a level surface for this method to work correctly. This Stadia range finding is good for locating topographic details such as fields, rivers, bridges, buildings, and roads.An instrument equipped for stadia work has two horizontal stadia marks spaced an equal distance from the center crosshair of the reticle. The distance between the stadia markings usually have a stadia interval factor of 100. This is important to know when calculating the distance between the instrument and the stadia rod.
To estimate distance with the stadia measuring method, hold the stadia rod so that it can be seen between the two stadia marks on the instrument's reticle (as pictured). With the Stadia Surveying Instrument focused on the rod, read the measurement markings on the stadia rod shown between the two stadia markings. The formula to calculate distance is D=R*S (Distance = Rod Reading Multiplied by the Stadia Constant.) The stadia constant is indicated on your instrument’s Users Manual. Most surveying Instruments have a Stadia constant of “100”. Therefore, if 6 feet is indicated on the rod, then the distance from the telescope to the rod is 600 ft. The calculation would look like this 100 * 6 ft = 600 ft. Stadia can give results accurate to about 1 foot under ideal conditions.
The stadia method of distance measurement is primarily used by professionals for a quick rough estimate and by those who primary task is not surveying. If you have any more questions about surveying instruments or would to purchase a tool to help you calculate stadia please visit EngineerSupply.com
