2011 - Geoinformatics

A r t i c l e
ALTM and Large Format Digital Photography
Simultaneous Data
Blom have a long history of owning and operating a range of digital cameras and sensors across
Europe. Traditionally, these instruments would be used independently, even if multiple data formats
were required. However, the demand for higher quality resources, and the need for improved capture
efficiency, has seen the long established techniques of aerial surveying put under the microscope. One
method to emerge is to use aircraft with dual sensor capabilities. In early, 2011 Blom UK adapted one
of their aeroplanes to enable simultaneous data capture with their Vexcel large format digital camera
and Optech ALTM LiDAR system.
By Hamish Grierson
The Second Hole
Cutting a hole into the fuselage of an aircraft is not as simple as
one may initially think, especially if the plane already contains a
large survey hatch. Before the hole can be cut several things need
to be considered. Will the control cables that run under the cabin
floor need to be rerouted? What is the strength and air worthiness
of the plane and how many alterations will be required? What are
the logistics of fitting the equipment and operators into the cabin
and will everything fit? Lastly, timescale and costs need to be considered.
How long will the plane be out of service and how much
will it cost, both in down time and in parts and labour?
Figure 1 - Both sensors are located on the right of the aircraft and the operator sits between them.
6
The original concept was to add a second full size survey hatch.
Following many discussions it was deemed that, with the engineering
taking up to six weeks, this would be too expensive. More importantly,
it became apparent that a full size hole was not actually
required. The ALTM head is a much smaller unit than the digital camera
so it does not require such a large hole. It could, in fact, utilise
the existing “Nav-Sight” hole.
Before the advent of GPS, nav-sights were used by operators of large
format film cameras to ensure the camera was taking pictures at the
required rate and over the correct location. The nav-sight sat in front
of the operator’s seat and required a small hole in the aircraft floor
October/November 2011