UKIAH -- Trimble Navigation Limited (NASDAQ: TRMB), a Sunnyvale-based developer of GPS and automation devices for farming and other commercial uses, is closing a Ukiah firm that it acquired in 2009.

Four of the six employees will stay with the company and work remotely after the closure, one as a consultant.

Formerly NTech Industries, the Ukiah firm invented technology that allows farming equipment to sense nearby crops, depositing a precise amount of fertilizer or herbicide as needed. Trimble bought the company to integrate the technology with devices that automate farming, allowing tractors and other equipment to work fields without the aid of a driver, said John Lovell, who managed the integration of the firm.

Some late-stage assembly of the devices was done in Ukiah at the time of the acquisition, but all of the manufacturing has since moved to Burlingame, he said.

With a low density of employees at the Ukiah location, Trimble decided to close the building and have the remaining employees work remotely.

"It got to the point where it didn't make sense for us to maintain the building here," said Mr. Lovell. "We don't take the decision lightly -- we're very aware of the personal impact."

Founded in 1978, the $1.5 billion-dollar company does the majority of its engineering in Sunnyvale but has employees in more than 20 countries.