HOUSTON—When people in distress call 911, dispatch centers immediately start tracing their locations.

Cell phone callers can be found in two ways: By a process called triangulation or by a GPS chip in the phone.

But, as evidenced in the tragic death of 20-year-old Kristin Sanchez, that isn’t always enough.

Sanchez drowned after flipping her truck into a small pond on a rainy April night.

She wasn’t able to tell the operator where she was.

Even so, the dispatch center tracked her location using triangulation, which finds callers by pinpointing their phone signals as they bounce off nearby towers.

But even though they found her signal, rescuers were unable to reach her before she died.

Why?

The Galveston County Appraisal maps in the 911 system didn’t show the pond.

Rescue officials set out looking for other nearby bodies of water instead.

“They didn’t see the body of water. It’s relatively hard to find from the road unless you’re familiar with it,” Bobby Wright of Galveston County Emergency Communications said.

If a caller phones in from a late-model device, dispatch may not be able to use the GPS method of location, since old phones weren’t equipped with that technology.

Whether or not a phone has GPS capabilities also depends on the carrier.  Emergency officials said Sprint, Nextel, Verizon, Cricket, T-Mobile and AT&T have the service in their new devices.

Sadly, in Sanchez's case, her phone was equipped, but even that couldn't guarantee her safety.

Officials suggest you contact your carrier to see if your particular phone has the technology.