Staff at the national mapping agency Ordnance Survey are to stage a 12-hour strike in a row over pay.
More than 1,000 union members will walk out of the Southampton headquarters, as well as other UK offices, on Tuesday.
Prospect and the Public and Commercial Services union claim staff's pay expectations are not being met.
Ordnance Survey bosses are disappointed with the outcome of the industrial action ballot, but said only a third of the workforce voted to strike.
Nadine Grant, head of human resources at the government agency, said: "We have worked very hard with trade union representatives to reach agreement on our latest pay offer.
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Members now feel they have no other avenue open to them
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"It is a high priority for us, but we can only fund what we can afford."
Ben Middleton, negotiator from the union Prospect, said: "Members now feel they have no other avenue open to them other than strike action.
"Ordnance Survey management has failed to respond to their reasonable expectations to have pay protected against inflation and for staff to progress to the rate for the job in a realistic time frame."
He added: "Ordnance Survey have stubbornly refused to acknowledge that staff who have patiently borne a succession of poor pay offers feel that patience has run out."