|
|
Demystifying Advancements in Digital Orthophotography
by Surdex Corporation, St. Louis, MO
About Surdex Corp.
Direct Camera Orientation Measurements
The purpose of aerial triangulation in the photogrammetric production process is to
establish precise and accurate relationships between the individual photographic film
coordinate systems and a defined datum and projection. This relationship is used to link
the ground surveyed control points via photographic measurements. This activity is often
termed “geo-referencing” of the aerial imagery.
Traditionally, the photogrammetrist takes photographic measurements with precise
photogrammetric instrumentation to be processed through computer algorithms; this
process is designed to eliminate blunders and systematic errors from the data while
minimizing the residual random errors within the entire triangulation network. The result
of the triangulation is a densified set of ground control points that are used to control the
remainder of the mapping process. The triangulation can be thought of as an
interpolation process where a dense pattern of ground control points, known as pass
points, are interpolated from a sparse pattern of surveyed ground control points and
Airborne GPS (ABGPS) control points.
Surdex employs the POS/AV 510-DG Applanix device for direct geo-referencing of
aerial photography. When used in conjunction with Airborne GPS exposure station
control and aerial camera systems, the inertial measurement unit (IMU) of the device
measures the camera’s six exterior orientation parameters to an accuracy that enhances
and in some cases even eliminates the fully analytical aerial triangulation process. The
POS/AV 510-DG provides highly accurate position and orientation data specifically for
airborne photogrammetric applications. It uses strapdown inertial sensors, Kalman
filtering and Airborne GPS, to measure the aerial camera’s position (x, y, and z) and
orientation (roll, pitch, and yaw) to an accuracy at the level of 0.328 feet RMSEposition and
20 arc seconds RMSEorienation or better on the ground from an altitude of 3280’ without
aerial triangulation.
Some of the benefits of using an Applanix device in conjunction with Airborne GPS
exposure station control for direct geo-referencing of aerial photography include:
- Minimum number of ground control points required
- No required analytical aerial triangulation in some cases depending on final
product accuracy requirements
- Higher level of horizontal and vertical accuracy and precision for
photogrammetric mapping
- Expedites mapping process by as much as three months for large, multi-faceted
projects
This is of great benefit to our clients by significantly reducing project time and cost.
Next
|
|
Sponsored by:
For information
regarding
advertising rates
Click Here!
|
