Why All The White Targets?

Small white X's or crosses have been staked in the grass near intersections in Tulsa for years. They've been ignored by most people, but not Bill Thomason. Thomason e-mailed News On 6's Rick Wells asking for answers. Rick checked around and found they are special markers used for aerial mapping.

One "X" or target is at 41st and South Utica. The News on 6 sent SKYNEWS 6 up to have a look from the air. It's from the air that these markers are important. There are lots of them. They are used to help orient aerial photographs.

Eric Andelin is the Vice President of Aerial Data Service, a Tulsa-based company that does aerial mapping all over the Western US. Those X's are used in a process called photogrammetry, surveying and mapping using aerial photographs.

"We can get down so close we can determine how much pavement is put on a new road," said Eric Andelin with Aerial Data Service.

The computer program analyzes the photo in 3-D. Dennis Fisher is the Tulsa Production Manager for ADS. He's like the Chief Photogrammetrist. Special glasses help the photogrammetrist see what the computer sees.

"Another thing it's good for is flood plain studies," said Andelin.

They are determining runoff and where the problems are and how to correct them. Periodically they fly over and photograph Tulsa County and the City of Tulsa

"What we are providing the city is an entire photo mosaic of the entire city," said Andelin.

That will be about 800 pictures. The white X's allow the photogrammetrist to line up overlapping images and put together an accurate mosaic. The same series of photographs can be used for several purposes. So, those big white X's ultimately save us time and money.

When an area of the city experiences big changes, like the area around the BOK Center, it can be re-photographed.

The white X's will help accurately fit the new photo into the overall mosaic.