Two trampers have been lifted by helicopter from an unstable slip face in the lower North Island's Ruahine Ranges today - texting their coordinates so their rescuers could fly straight to them.

The pair, a man and a woman, were traversing the slip face when they realised it was unstable and they were unable to moved either forwards or back, said Inspector Anaru George of police central communications.

Cellphone coverage in the area was limited. It was not good enough for them to ring out but just good enough for them to send and receive texts, although some were garbled.

They sent a text message "stuck on a slip face, were ok but not safe" to a friend, who contacted police about 10am.

Police were able to text the trampers in order to identify their exact location and nature of their emergency, Mr George said.

They were able to supply their GPS coordinates, he said.

A helicopter was able to pinpoint the trampers quickly and winched them from the unstable slip face about midday.

They were extremely well equipped which made their extraction from their predicament very easy, Mr George said.

Normally the biggest problem was finding trampers in trouble, but not in this case, he said.

"They had everything going for them, except knowledge of the terrain that was falling away from under them."

In one of the final text messages to the police central communications centre, the trampers wrote "Thank you so much for your help. We are sorry to have ruined your saturday".