Both forms are correct but different.
Data - collective noun,
uncountable
Radar data is used to track the aircraft.
Data - noun, plural (sg. datum)
countable
The following data are used in the flight data processing:
- radar data;
- flight plan data.
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Citeaza
Main Entry:
da·ta Listen to the pronunciation of data Listen to the pronunciation of data
Pronunciation:
\ˈdā-tə, ˈda- also ˈdä-\
Function:
noun plural but singular or plural in construction
Usage:
often attributive
Etymology:
Latin, plural of datum
Date:
1646
1 : factual information (as measurements or statistics) used as a basis for reasoning, discussion, or calculation <the data is plentiful and easily available — H. A. Gleason, Jr.> <comprehensive data on economic growth have been published — N. H. Jacoby>
2 : information output by a sensing device or organ that includes both useful and irrelevant or redundant information and must be processed to be meaningful
3 : information in numerical form that can be digitally transmitted or processed
usage Data leads a life of its own quite independent of datum, of which it was originally the plural. It occurs in two constructions: as a plural noun (like earnings), taking a plural verb and plural modifiers (as these, many, a few) but not cardinal numbers, and serving as a referent for plural pronouns (as they, them); and as an abstract mass noun (like information), taking a singular verb and singular modifiers (as this, much, little), and being referred to by a singular pronoun (it). Both constructions are standard. The plural construction is more common in print, evidently because the house style of several publishers mandates it.
source: merriam webster