104
3 Non-geometry standards
(measured depth) d
r (range= 112 of2-way travel time)
IE---- Y ----'!li
(cross-track distance)
Fig. 3.26. Position and depth ealculation for a hydrographie sonar (IS057 2003)
The scanning linear array type sensor scans the terrain within the field of view
under the flight track. This sensor scans along one scan line using a rotating mirror.
Focal plane
~ Rotating
V-~ scan IlllITOr
1\\
1\ ~
I
\
I \
I \
I \
,
\\ Scan direction
///7
Fig. 3.27. Optieallayout of a linear seanning sensor. The other types of sean linear arrays are
eonie seanning and whiskbroom seanning sensors
The pushbroom sensor takes the data along a scanline at one moment.
Most of the scanning linear arrays and pushbrooms are flown on satellite platforms. As the orbit is smooth compared to the ground resolution the resulting image
may be georeferenced by robust transformations (sensor reference, rigorous model)
or by functional relations such as polynomial transformations (image reference). If
the scanning linear array type sensor is operated from an aeroplane, a line by line
rectification is necessary to georeference the data.