Automatic tank gauging, or ATG, replaces climbing a tank and dropping a gauge line with continuous, remote measurement of what is in the tank. It underpins inventory management, custody, and overfill protection across upstream and midstream storage. This guide explains what an ATG system is, the gauge technologies it uses, and how its data reaches SCADA.
Automatic Tank Gauging (ATG) in one line: Automatic tank gauging (ATG) is the continuous, automated measurement of a storage tank's liquid level - and usually temperature and inferred volume - using an in-tank gauge such as a radar, servo, or float device, instead of manual hand gauging. It feeds inventory, alarms, and custody calculations.
At minimum an ATG measures liquid level continuously. Because oil volume changes with temperature, a full ATG also measures product temperature (often at several depths with a multi-spot temperature probe) and combines level, temperature, and the tank's geometry to report gross and net standard volume. Many systems also read the oil-water interface level and, on larger installations, density and water bottoms.
The output is inventory a person can trust without climbing the tank: how much product is on hand, how fast it is moving, and how much room is left. That is the basis for scheduling hauls or pipeline transfers, reconciling movements, and triggering high-level and overfill alarms.
Non-contact radar gauges send a microwave signal from the top of the tank and time its reflection off the liquid surface; they are accurate, have no moving parts in the liquid, and are common on new installations. Servo (displacer) gauges suspend a small displacer on a wire and continuously balance it at the surface with a servo motor, giving very high accuracy for custody and also reading interface and density. Guided-wave radar runs the signal along a probe for narrow or turbulent tanks.
Older and simpler installations use float-and-tape or magnetostrictive float gauges, where a float rides the surface and its position is read mechanically or electronically. For custody-grade inventory, accuracy classes are defined by standards such as API MPMS Chapter 3.1B; the gauge choice follows how tight the measurement must be.
An ATG gauge outputs its readings over a fieldbus or serial protocol to a tank-side transmitter or an ATG console, which exposes level, temperature, and volume as data points. Those are wired into an RTU, flow computer, or PLC, or read directly by the supervisory layer, and become tags such as TANK3_LEVEL and TANK3_NET_VOL.
A cloud SCADA such as Merobix reads those ATG-derived tags over Modbus, DNP3, or OPC UA, so tank inventory, fill rate, and overfill alarms across an entire field or terminal appear on one dashboard. That turns per-tank gauging into fleet-wide inventory visibility and lets hauling and transfers be scheduled from the data rather than from site visits.
It is the continuous, automated measurement of a tank's liquid level, and usually temperature and inferred volume, using an in-tank gauge such as radar, servo, or a float - replacing manual hand gauging. It provides live inventory, movement rates, and overfill alarms for storage tanks.
Common technologies are non-contact radar, guided-wave radar, servo (displacer) gauges, and float-based gauges such as magnetostrictive or float-and-tape units. Radar and servo gauges offer the highest accuracy and are used for custody and inventory; float gauges are simpler and lower cost.
A basic ATG measures level, but a full system also measures product temperature and applies the tank's strapping table to report gross and net standard volume. Servo and advanced systems can also read the oil-water interface, density, and water bottoms, giving custody-grade inventory rather than just a level.
Safety & engineering notice. This article is general educational information, not site-specific engineering, safety, or legal advice, and it does not reflect any particular facility. Standards and regulations (for example OSHA, API, IEC, ISO, NFPA, NIST, and NERC CIP requirements) change and vary by edition, jurisdiction, and application. SCADA and remote monitoring cannot verify physical isolation, atmosphere, lockout/tagout, permit status, or a safe go/no-go decision. Qualified personnel must perform site-specific engineering, hazard analysis, and safety review, and confirm current requirements with the authority having jurisdiction, before acting.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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