Transcript Document

VIIth International Scientific and Technical Conference
From Imagery to Map:
Digital Photogrammetric Technologies
ADS40 imagery processing
using PHOTOMOD:
technology and experience
Petr S. Titarov,
Software Developer
September 17-20, 2007, Nessebar, Bulgaria
Report outline
 ADS 40 image acquisition
 Software involved and data flows
 Solving space intersection and resection problems
 Processing ADS40 using PHOTOMOD
 Pilot project: creating 1 : 2 000 orthoimagery
ADS 40 image acquisition
ADS 40 Level 0 imagery
Level 0 image
ADS40 Level 0 images
are distorted due to
pushbroom imaging
mode and exterior
orientation instability.
Exterior orientation
X
w
Y
f
Z
k
ADS 40 Level 1 imagery creating
The Level 1 image is generated by
projecting Level 0 image onto the
constant height plane in the Local
Space Rectangular (LSR) reference
frame using in-flight (not adjusted)
exterior orientation.
Level 0 vs. Level 1
Level 0 image
Level 1 image
As compared with Level 0 images, the Level 1 images are non-distorted,
comfortably viewable, suitable for automatic tie points measurement.
Specific aerial pushbroom imagery artifacts
On the edge of the image
Inside the image
The gaps on the ADS40 Level 1 images are caused by abrupt exterior orientation change.
Level 1 images edges
AN-30
L-410
Data flows between software involved
GPro
Sensor calibration
(*.cam)
In - flight exterior
orientation (*.odf)
Level 0 imagery creation,
automatic tie points
measurement
Ground control
and tie points
ORIMA
Block adjustment
Level 1 imagery creation
Level 1 imagery + metadata (*.sup) +
sensor geometric calibration (*.cam) +
in-flight exterior orientation (*.odf)
PHOTOMOD
DTM/DEM extraction,
2D/3D vectorization,
orthoimagery creation
Adjusted exterior
orientation
(*.odf.adj)
GPS/IMU software, GPro, ORIMA…
GPS/IMU software
Post-processing of the in-flight
GPS/IMU measurements:
 POSProc/ POSGPS
 GrafNav
GPro
Image download from on-board
storage, Level 0/1 imagery generation
ORIMA
ADS 40 block
adjustment
PHOTOMOD Software
PHOTOMOD DTM
DTM derivation
PHOTOMOD StereoDraw
3D Vectorization
PHOTOMOD Mosaic
Orthomosaic generating
PHOTOMOD Vector
Digital map creating
Space intersection and space resection problems
Space intersection
 xleft 


X 
    y left 
Y  f
x right 
Z 


 
y 
 right 
Space intersection is
solved to derive DTM.
Space resection
x
  
 y
X

g Y
Z






Space resection is solved
to create orthoimagery.
Solving space resection problem by Level 1 image
Level 1 space resection solving scheme
LSR
coordinates
X,Y,Z
LSR coordinates of the Level 0
image point projection onto the
rectification plane
Level 0 image
coordinates
Adjusted
orientation
In-flight
orientation
l0 , p0
Xp, Yp, H
Level 1 image
coordinates
Affine
transformation
l1 , p1
Level 0 space resection
Level 0 space resection
Solving Level 0 space resection problem is time-consuming
operation due to pushbroom image acquisition mode and
the instability of the airborne sensor exterior orientation.
The procedure consists of three stages:

Iterative contracting the search area (estimating line
and detector number ranges);

Sequential line number search throughout the range;

Calculating detector number using line number found;
Solving space intersection problem by Level 1 stereopair
Level 1 space intersection solving scheme
Left Level 1 image
coordinates
l1left , p1left
LSR coordinates on
the rectification plane
Affine
transformation
X r.p. left ,Yr.p. left , Hr.p. left
Left
Level
0
image coordinates
In-flight
orientation
l0left , p0left
Level 0 space resection
LSR coordinates
Adjusted
orientation
Right Level 1 image
coordinates
l1right , p1right
LSR coordinates on
the rectification plane
Affine
transformation
Xr.p. right ,Yr.p. right , Hr.p. right
Right
Level 0
image coordinates
In-flight
orientation
l0right , p0right
Level 0 space resection
Level 0 space intersection
X,Y,Z
Selecting images for processing in PHOTOMOD
Stereo processing
14 ̊ backward + nadir
nadir + 28 ̊ forward
B : H = 0.25
B : H = 0.53
Best correlation, but
worst stereo precision
14 ̊ backward + 28 ̊ forward
B : H = 0.78
Best stereo precision,
but worst correlation
Orthoimagery creating
Orthoimagery should be created using
nadir images to minimize the influence of
DTM errors on the orthoimage accuracy.
PHOTOMOD project structure for ADS 40 processing
Since the block adjustment of ADS 40 data is performed by ORIMA,
there is no reason to insert the entire block into single PHOTOMOD project.
Project structure in the case of stereopair
composed of nadir and off-nadir images
Project structure in the case of stereopair
composed of backward and forward images:
the nadir image is added into separate strip.
The orthomosaic is created using capability
of PHOTOMOD Mosaic module to involve
images from several PHOTOMOD projects.
Adding ADS 40 images into the PHOTOMOD project
Level 1 support file (*.sup)
ORIGINAL_ORIENTATION
In-flight external orientation file (*.odf)
ADJUSTED_ORIENTATION
Adjusted external orientation file (*.odf.adj)
ORIGINAL_CALIBRATION
Interior orientation file (*.cam)
IMAGE_FILE_NAME
Image file (*.ads)
BLOCK_DATA
Raster (0,0) (*.tif)
Raster (0,1) (*.tif)
...
Automated folder
analysis and data
search
Radiometric enhancement
Focus on reference systems
Local Space
Rectangular
PHOTOMOD project
reference system
The exterior orientation is given with respect to
LSR (Local Space Rectangular) reference system.
So the connection between PHOTOMOD project
reference system and LSR should be provided.
There are two ways to establish the connection:

To measure at least three points with known
ground coordinates on the stereopair (shift –
rotation – scale seven parameters set will be
calculated);

To specify completely the PHOTOMOD project
reference system - datum, map projection etc.
Pilot project: 1 : 2000 orthoimagery production
Source data
 images GSD:
20 cm
 strips number:
 data (L0&L1) volume:
24
0.5 Tb
Output orthoimagery
14 ̊ backward + nadir
stereopairs were used
to derive DEM for
orthoimagery creating
 scale:
1 : 2 000
 sheets number:
 orthoimagery area:
351
91,25 km2
Pilot project: workflow
GPS/IMU post-processing
S
T
E
P
B
Y
S
T
E
P
GPro
ORIMA
PHOTOMOD Montage Desktop
PHOTOMOD AT
PHOTOMOD DTM
PHOTOMOD Mosaic
In-flight exterior orientation data preparation
Level 1 imagery generating
Block adjustment
PHOTOMOD projects creating
DTM extraction from stereopairs
Deriving orthomosaic using images and DEMs
from several PHOTOMOD projects
Pilot project: check points





points number :
strips number:
images GSD:
X,Y mean errors:
Z mean error:
15
24
20 cm
20 cm
30 cm
Pilot project: orthoimagery samples
Panchromatic
Color
Thank you for your attention!
THE END