FORT LAUDERDALE, Fla. -

Local surveying firms are being told to lock up their equipment because thieves are targeting the tools of their trade.

Bob Krisak, with Keith and Schnars, P.A., in Fort Lauderdale, said nearly a dozen South Florida surveying firms have been hit in the first three months of this year.

"Absolutely, no survey firm today can function without them," said Krisak.

The crooks are stealing the electronics and GPS devices that measure and map building sites, and the computers used to store the data.

You frequently see surveyors using this stuff on the street. Krisak said that's usually where it's stolen.

"For some reason over the past three months, they must have realized it was more beneficial to them to go right to the source," Krisak said.

Surveillance images from a heist last weekend in Miami show four thieves prying open a door and leaving in a black pickup truck.

Two weeks ago, Krisak said his firm was hit and they got away with a dozen data collectors valued at $3,500 each.

Police are puzzled because the highly specialized equipment is not something you'd fence at a pawn shop or even sell on eBay.

"It could be used at some location where there's some construction going on or maybe it's being exported. It's really unclear," said Fort Lauderdale police Detective Deanna Garcia.

The Florida Society of Surveyors and Mappers is warning its South Florida members to lock up their equipment. The trade association is also working with police to connect the dots on these crimes.

"There are other companies that lose equipment and they are wiped out, and they can't do anything until they replace the equipment," Krisak said.