A helicopter's infra-red thermal imaging camera helped save a mother and her young son after they became stranded in an isolated ravine.

The 29-year-old woman used her mobile phone to call for help after she collapsed near a stream in the middle of Shipley Glen, Baildon as darkness fell last night.

The crew of the police helicopter, called from Wakefield, spotted the woman trapped among the rocks using the specialised cameras.

They then lit up the whole area with powerful spotlights to guide rescue teams on the ground to the woman, who police have not named.

She was eventually found, tearful and shivering, near some rocks with her seven-year-old son by her side 45 minutes after the alarm was raised as temperatures dipped to six degrees Celsius.

Two fire crews from Bradford and one from Bingley helped paramedics stretcher the woman to a waiting ambulance in Coach Road which took her to Bradford Royal Infirmary.

The boy was returned home to be looked after by other family members.

West Yorkshire Police spokesman David Robinson said: "The woman had gone out for a walk with her seven-year-old son and got lost in a wooded area.

"Fortunately she had a mobile phone with her which she used to contact the police.

"Our helicopter came out and illuminated the area and used thermal imaging equipment to find her.

"Both the child and the woman were uninjured but it appears she had an old leg injury which was playing her up.

"I don't know how we would have found her if she hadn't had the mobile phone. They were very lucky."

Sub Officer Andy Newman from Bradford fire station was among the crews on site.

He said: "By the time we arrived she was on a stretcher and we helped carry her out of the glen.

"She was very upset and crying in pain but you couldn't tell what injuries she had.

"They found her right down at the bottom of the glen and if she hadn't had the mobile phone she may well not have been found until this morning by someone walking their dog."