Datum Peg
Definition
A fixed ground marker with precisely recorded coordinates that serves as the origin point for a site grid. All spatial measurements on the site are expressed relative to the datum network, so the data remain consistent across survey sessions and surveyors.
- Field
- Crime scene / excavation surveying
- Type
- Fixed ground marker with recorded coordinates
- Function
- Origin point for the site grid
- Benefit
- Keeps measurements consistent across sessions/surveyors
Common questions
What happens to the reliability of a site's spatial record if the datum peg is disturbed mid-investigation?+
Every measurement recorded relative to that datum after the disturbance becomes suspect because the origin point may have shifted, so scene protocols typically require multiple redundant datum points and periodic verification checks to detect and correct for any accidental movement before it corrupts the spatial dataset.
Why use a fixed datum peg rather than just recording GPS coordinates for each find independently?+
A shared local datum lets multiple surveyors and instruments produce measurements that agree with each other to a precision finer than consumer GPS typically achieves, and it keeps the site's internal spatial relationships accurate and reproducible even if absolute GPS coordinates carry some error.
Related terms
- Backsighting
- The process of orienting a total station by pointing it at a known reference point (backsight) after setting it over the instrument...
- Resection
- A method of determining the instrument station's own coordinates by measuring angles and distances to two or more points of known position....
- RTK-GPS
- Real-Time Kinematic Global Positioning System: a satellite-positioning technique where a static base station transmits correction data to a roving receiver in real...
- Site Grid
- A rectangular coordinate system established across a site, usually with the origin at a datum peg and axes aligned to magnetic north...
- Total Station
- An electronic instrument that simultaneously measures horizontal and vertical angles and distance to a reflective prism, computing three-dimensional coordinates directly. Typical angular...