Summer readers find their way

WILLIAMSBURG — Gabby and Tynleigh Troyer, of Williamsburg, hunted for clues in the Williamsburg city park using GPS devices provided by the Iowa County Conservation department.

Part of the summer reading program, the hunt taught children and adults how to find locations on the earth using electronic devices and compasses.

Mary Blair, naturalist with Iowa County Conservation, showed step-by-step how to use a GPS device to find a location, using the hobby geocaching as an example.

“Geocaching is a real fun outdoor activity,” said Blair.

“Geocaches can be anything.” Some are boxes with trinkets in them, some are small containers, some are larger.

Geocache.com uses GPS coordinates to tell hunters where to find the caches. They can use the app on their phones or specialized GPS devices.

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The first step is to find the satellites that will pinpoint the location. “To find an exact location, you have to. hook to three satellites,” said Blair. They triangulate to provide an exact location to within a few feet.

There are 24 satellites in orbit.

The GPS shows a person’s current location in latitude and longitude. To find a different location, such as the location of a geocache, a person changes the latitude and longitude to the desired destination, then accesses a map on the device.

The latitudes and longitudes don’t have to be entered manually on the geocache app. The location is entered by whoever placed the cache. Anyone who looks for the cache using the app can simply touch the icon and follow the line to the cache.

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As with the GPS locations, the direction is shown “as the crow flies,” said Blair. Reaching the cache may require walking around natural or man-made objects.

The GPS can’t pick up satellite signals when a person is standing still, said Blair. And they don’t pick up signals well in buildings or underground.

Sometimes an electronic device is not available, and the GPS won’t work unless it can access satellites. So Emma Edelen, summer naturalist with Iowa County Conservation, demonstrated how to use a compass.

“It’s nice to have a compass with you just in case,” said Edelen.

“You have to hold it flat,” Edelen said, keeping her compass close to her body and parallel to the floor. “Your direction is always pointing out from you.”

Edelen explained that compasses work because the earth is magnetic due to its molten core. The red arrow on the compass will point to the North Pole, which is magnetic south, Edelen said. Opposite poles attract, she said.

“I’m a science teacher,” confessed Edelen as she explained magnets and the earth. During the school year she teaches earth science to ninth graders in Cedar Rapids.

Every 300,000 years, the poles flip, said Edelen. Right now, magnetic south is at the North Pole.

Edelen showed her audience how to make a compass by rubbing a paper clip on a magnet, then laying it on a piece of foam floating in water. The paper clip becomes magnetized and points north.

After learning global positioning satellites and compasses, children and adults followed Blair and Edelen to the city park where they used the GPS devices to find letters hidden around the park.

They also followed directions with their compasses, walking in small patterns according to direction and distance.