Leica ADS-40

Lecture 7
ADS 40 Camera and Imagery

Leica ADS-40
• ADS – Airborne Digital Scanner
• Used in the current , province wide, aerial imaging for the primary purpose of creating
the forest resource inventory.
• Succeeded first ADS-80.
• CCD lines having 12000 pixels each.
• Detector (pixel) size: 6.5 μm
• Dynamic range CCD chain
(radiometric resolution): 12 bit
• Spectral bands (in nm)
o Panchromatic 465 – 680
o Red 610 – 660
o Green 535 – 585
o Blue 430 – 490
o Near-infrared 835-885
• Field of View (swath angle): 64⁰

Leica ADS-40
• The pushbroom scanner takes seamless panchromatic images from three different
angles (allowing for stereo viewing), creating three separate scenes:
•The fact that each point is scanned three times, from three different angles, also helps in
stabilizing the image geometry, since the pushbroom scanned images have inherently poor
geometry (each strip represents an independent image!) (Mikhail et al. 2001).

• ADS-40 CCD sensor contains several lines, i.e.,
the sensor can simultaneously take several
seamless image strips.
• Image strips are taken at different angles to
allow for stereo viewing.
• Angles and spectral makeup of the imagery
can be customized for specific project needs.
• Camera can be set to take image strips at
different angles. eFRI imagery is captured in five
different image strips: RGB & NIR at 16⁰
backward and at nadir, panchromatic at 14⁰
backward, and at 2⁰ and 27⁰ forward.
• Each line has 12000 pixels along it.
• Panchromatic lines pixels are staggered
laterally by 0.5 pixels, halving the resolution –
panchromatic resolution for eFRI is 20 cm and
RGB & NIR resolution is 40 cm.
Leica ADS-40
-16⁰
RGB
NIR
-14⁰
0⁰
PAN RGB
NIR
2⁰
27⁰
PAN PAN

• A trichroid beam
splitter ensures that the
RGB colours from the
same place,
represented by a pixel,
are separated into RGB
components.
Leica ADS-40

Leica ADS-40
From Paternaki (2006).

In the eFRI system, there are several separate product levels created from
the ADS-40 imagery.:
Level 0: raw imagery
Delivered by the MNR:
Leica ADS-40
Level 1: stereo image strips – georeferenced but not ortho-rectified.
o A single band panchromatic image strip , 16 bit and a ground
resolution of 20 cm at forward, nadir and backwards view angles.
o A four band multispectral (R, G, B, NIR) image strip, 16 bit and a
ground resolution of 40 cm at nadir and backwards angles.
Level 2: ortho-rectified (planimetrically correct imagery -- true horizontal
distances, such as on topographic maps) strips and 5x5 km tiles.
o A single band, panchromatic, 16 bit, 20 cm ground resolution.
o 4 band (R, G, B, NIR), 16 bit, 40 cm ground resolution.
Digital Surface Model (DSM), points with surface elevations, at 5 m
ground resolution.
Classified DSM – points classified in vegetation (trees), water and
ground.
Level 0
Level 1
Source: Paternaki
(2006).

Leica ADS-40
• The camera itself is part of a complex computer and navigation system.
1 - Sensor (Camera) Head
with:
• Digital Optics
• IMU (Inertial
Measurement Unit)
2 – Control unit with a
position and attitude
computer POS (Position
and Orientation System).
3 – Mass Memory
4 – Operator Interface
5 – Pilot guidance Indicator
6 – Mount PAV30 (gyro
stabilized mount).
Source: Fricker (2001).
Two other systems can be defined as part of the aerial
photo flight operation:
• Flight and Sensor Control Management System
(FCMS)
• Attitude and Position Measurement System

Leica ADS-40
Camera Head
Source: Pateraki (2006)
• The focal plane module
consists of four CCD
housings: two of them
contain single lines and
two contain triple lines.
• Each CCD line consists of
two linear arrays, each
with 12000 pixels, size
6.5μm, but staggered by a
0.5 pixel shift.
• The panchromatic lines
make use of the staggered
arrangement, whereas the
colour lines (RGB, NIR1,
NIR2) do not (Sandau et al.
2000)

Leica ADS-40
Gyro-stabilized camera mount PAV30
• Compensates angular aircraft
movements
o Pitch and roll -- within ± 5°
o Crab -- within ± 30°
• This allows for taking true vertical
imagery.
• As a result, simplified
aerotriangulation.
Source: Lecia PAV30 http://www.leicageosystems.com/downloads123/zz/airborne/gener
al/brochures/PAV30_Brochure.pdf

Leica ADS-40
Control Unit (Camera Computer) Within the System
The Image Data Processing unit
compresses the image data
provided by the camera head in
real-time. It does the
compression at a rate of up to 40
MB/s in two optional modes,
lossless and JPEG.
Source: Sandau et al. (2000)
Stores all mission
data – image,
orientation and
housekeeping
data.

Source: Sandau et al. (2000)
Leica ADS-40
Flight and Sensor Control Management System (FCMS)
• FCMS controls, coordinates and monitors individual subsystems and provides a graphical
user interface.
• The system can be used on ADS-40 but also on a number of other sensors made by Leica
Navigation System
GNSS (GPS) supported navigation – navigation
and graphical guidance is displayed during all
phases of the survey flight.
Flight & Error Data Log
Data, e.g. flight track, start and stop of imaging
sequences, sensor parameters, are stored for
precise evaluation, optimization and
maintenance.
Flight Managemet
• Different displays of suggested flight path, approach
and turns for operator and pilot.
• Keeps track of flown, not flown and lines that need to
be re-flown (because of, e.g., clouds).
• Vector data and ground control points as a backdrop
for flight guidance.
•Optimized guidance information for flight lines to be
flown.
Sensor Control
• Interfaces the hardware and allows for different
parameters to be transferred to the hardware and
status information read back.
• Automatic sensor release – starts and stops the sensor
according to the flight plan.
Test & Service Facility
Allows service technicians to locate and replace faulty
parts or update internal software.

IMU measures and
reports on a plane’s
velocity, orientation and
gravitational forces by the
use of accelerometers and
gyroscopes.
Relative orientation and
velocity from IMU and
absolute position and
velocity from GPS are used
to correct low-frequency
errors in the navigation
solution.
POS generates both a realtime
and post-processed
position and orientation
solution.
Leica ADS-40
Attitude and Position Measurement System
Source: Sandau et al. (2000)
POS has the ability to control automatically the
stabilised platform yaw, and to remove crab and
drift.

FCMS Interfaces

Frame Array Digital Imagery vs. Linear Array Digital Imagery
• Less time to mosaic (auto-triangulate, ortho-rectify) linear array digital imagery.
Source: Pateraki (2006).

Frame Array Digital Imagery vs. Linear Array Digital Imagery

Source: Pateraki (2006).
Digital vs. Analog Images

Source: Pateraki (2006).
Digital vs. Analog Spectral Sensitivity
• Non-overlapping bands are more suitable for controlled remote sensing analyses and
displays, whereas overlapping, film-type, bands are more suitable for high-quality, true
colour images.

References:
Fricker P. 2001. ADS40 – Progress in digital aerial data collection. Photogrammetric Week 01,
Institute of Photogrammetry. Heidelberg, Germany.
Mikhail, E. M., J. S. Bethel, and J. C. McGlone. 2001. Introduction to Modern Photogrammetry.
John Wiley & Sons, INC.
Pateraki, M. 2006. Digital Aerial Cameras. International Summer School “Digital Recording and 3D
Modelling”. Crete, Greece.
Sandau, R., B. Braunecker, H. Driescher, A. Eckardt, S. Hilbert, J. Hutton, W. Kirchhofer, E.
Lithopoulos, R. Reulke, S. Wicki. 2000. Design principles of the LH systems ADS40 airborne
digital sensor. International Archives of Photogrammetry and Remote Sensing. 33:B1.