Volume 30 Issue 1
News from GeoOne, Inc.
the same accuracy--and
save companies the cost
of ground control."
--OSU Professor Emeritus Dean Merchant
Professor Dean Merchant (at right)
and pilot Don Moore (left)
prepare for takeoff.
AIRBORNE GPS-
YOU CAN TAKE IT WITH YOU
A new twist on airborne GPS cuts the
costs and nails the numbers. Could it work for you?
From the forest primeval to urban jungles,
from highways to byways, 'in-situ' calibration for airborne GPS is
trimming project costs--without sacrificing accuracy.
Have Tools, Will Travel
It's a tight fit. The two-man crew is
stuffed like sardines into GeoOne's turbo-charged Cessna Centurion 210
aircraft with a video camera, 50 pound film magazine, TV-viewer and color
monitoring system. The professor is adjusting the camera, while the
pilot flies down the center of a pixelated line displayed on his ARNAV
navigational system, staying on the designated flight line.
The dignified white-haired professor projecting
intensity and enthusiasm is Dean Merchant. He is calibrating the
plane's GPS/photogrammetric system while airborne. Merchant has
played a leadership role in developing 'in-situ' calibration of airborne
GPS/photogrammetric systems, and is its leading proponent.
Which Ground Points are Pointless?
Using Global Positioning Systems (GPS) to
provide mapping coordinates is a foregone conclusion. Its advantages
are legendary. With 24 satellites and a few spares in orbit, and the
precision timing of atomic clocks, distances and measurements can be shown
with great accuracy.
Today, airborne GPS is cutting costs for
government agencies, engineering firms and corporations by eliminating
redundancy in ground controls--reducing the number of sites, say, from
thirty down to five. Traditionally, GPS is calibrated on the
ground. Accurate measurements are made in a laboratory
environment. However, when the camera is flying, it is subject to
different conditions that can cause systematic errors.
The camera--one of the world's most accurate--is gyro stabilized to the vertical, so the airplane may bump around, but the camera lens always points straight down. The GPS antenna is located directly over the camera. Today, the crew is flying 50 targets in a single photograph, to test distortion. Mathematical models are used to calibrate the camera. "It's likely to be five time more accurate," Merchant states.
Do More With Less
When is this useful? Merchant conducted terrain and topography studies for the Ohio Department of Transportation in 1997. "We were looking for ways to do more with less," he states. They ground-truthed targeted points and the results met accuracy standards. Moreover, they found:
- Airborne GPS can be a practical solution for highway engineering and design as well as high altitude GPS programs.
- It is accurate in hilly, forested areas, rural open areas and dense urban areas.
- Sufficient accuracy requires no targets except for
quality control purposes.
GeoOne's 'in-situ' calibrated airborne GPS is now operational.
SOAR
ABOVE
THE CROWD
Contact Judy Reimer
at 1-800-394-MAPS
to receive your
complimentary mouse
pad and discuss your
mapping projects.
Will this work for you?
We are constantly finding ways to maximize efficiency, increase accuracy
and help you achieve your goals. It's just one way GeoOne takes care
of its clients. For other ways--ask us!
