Milligal converter
Convert gravity survey readings between milligals and SI acceleration — the units of finding things underground.
That's 2× as strong as a buried cavity, while an ore body is 2× stronger. A 70 kg person would weigh about 0.07138 g more or less.
What it means
How big is that anomaly?
Survey readings must be corrected for latitude, altitude, tides and terrain before the remaining anomaly means anything about the rock below.
Every unit
Your reading in every unit
Learn
Three things worth knowing
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1 mGal = 10 µm/s²
And ordinary gravity is 978,000 to 983,000 mGal depending on latitude. The survey business lives in the last few digits.
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Named for Galileo
The gal — one centimeter per second squared — honors the man who first measured how things fall. Geophysics works in thousandths of it.
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Corrections are most of the work
Moving a gravimeter up by three meters changes the reading by a milligal, which is larger than most anomalies being hunted. Position matters as much as the instrument.
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Popular gravity conversions
Background
About gravity surveying
Gravity is not the same everywhere: it varies with latitude, altitude and what is buried underneath. Those differences are tiny — a few parts in a million — so surveyors use the milligal, a hundred-thousandth of ordinary gravity.
A buried cavity or an ore body shifts the reading by a fraction of a milligal, which modern instruments can measure from a moving aircraft.