Photogrammetric Analysis of Rotor Clouds Observed during T ... · Introduction Digital stereo...
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Photogrammetric Analysis of Rotor Clouds Observed during T-REX Ulrike Romatschke 1 , Vanda Grubišić 1 , and Joseph A. Zehnder 2 1 National Center for Atmospheric Research, 2 Southwest Weather Consulting, LLC Introduction Digital stereo photgraphs collected during the T-REX field campaign are used to: ● Develop algorithms for camera calibration, automatic feature matching, and reconstruction of 3D cloud scenes. ● Track the 3D path of cloud fragments at the upstream edge of rotor clouds and monitor their growth and dynamics until their merger with the main cloud. Data Camera calibration, feature matching, and 3D cloud reconstruction algorithms Results: Statistics from 37 clouds Conclusions The T-REX field campaign took place in Owens Valley, CA, in the lee of the Sierra Nevada. ● IOP 6: March 25, 2006, 08:40-16:50 PST ● Cameras: Cannon 20D digital 8 Mpixel ● Base line between cameras: 666m ● Shutter speed: ~10s We study the evolution of cloud fragments which form upsteam of a largely stationary rotor cloud. 1. Lens distortion correction and image enhancement. ● Grubišić, V., and Coauthors, 2008: The Terrain-Induced Rotor Experiment: A field campaign overview including observational highlights. Bull. Amer. Meteor. Soc., 89, 1513–1533. ● Hu, J., A. Razdan, and J. A. Zehnder, 2009: Geometric calibration of digital cameras for 3D cumulus cloud measurements. J. Atmos. Oceanic Technol., 26, 200–214. Algorithms have been developed for camera calibration, automatic feature matching, and reconstruction of 3D cloud scenes from stereo photographs. The resulting point clouds have: ● high spatial resolution (~m) which is only limited by the pixel size and the distance to the cameras ● high temporal resolution (~10s) High resolution 3D point clouds allow detailed analysis of cloud evolution parameters such as growth, and horizontal and vertical movement. 2. Calibration of all six camera angles relative to each other by minimizing the distances (d) of “sightlines”. 3. Transformation of camera coordinate system (x, y, z) to world coordinate system (longitude, latitude, elevation) using real world reference point visible in both images. 5. Calculation of 3D coordinates of matched pixels via triangulation, and reconstruction of 3D point cloud. 4. Automatic matching of left and right image pixels of selected cloud feature. Cameras Sierra Nevada Owens Valley Camera A Camera B Reference point Reference point Reference point Image from camera A Image from camera B Lon, lat, elev, from Google Earth d Camera A Camera A Camera B Camera B 0 19 Jan 22:00 20 Jan 00:00 20 Jan 02:00 20 Jan 04:00 Time 0s 30s 70s Image from camera A Image from camera B -118.162 -118.160 -118.158 36.650 36.652 36.654 3800 4000 4200 4400 Latitude [ °] Longi tude [ °] Elevation [m] 3800 4000 4400 4200 E l e v a t i o n [ m ] -118.162 -118.160 -118.158 Longitude [°] 36.654 36.652 36.650 Latitude [°] Sierra Nevada Owens Valley 0s 10s 20s 30s 40s 50s 60s 70s 0 0.5 1 1.5 Horizontal travel distance [km] 0 50 150 250 Elevation [m] 100 200 0 0.2 0.6 0.8 Cloud area [km 2 ] 0.4 0s 10s 20s 30s 40s 50s 60s 70s 0s 10s 20s 30s 40s 50s 60s 70s Horizontal speed [m/s] 0-10s 10-20s 20-30s 30-40s 40-50s 50-60s 0 10 20 30 40 -10 Vertical speed [m/s] -5 0 5 10 0 0.5 1 1.5 Travel distance of front and back edge [km] Front Back 0-10s 10-20s 20-30s 30-40s 40-50s 50-60s 0s 10s 20s 30s 40s 50s 60s 70s Contact: [email protected]
Transcript of Photogrammetric Analysis of Rotor Clouds Observed during T ... · Introduction Digital stereo...
Photogrammetric Analysis of Rotor Clouds Observed during T-REXUlrike Romatschke1, Vanda Grubišić1, and Joseph A. Zehnder2
1National Center for Atmospheric Research, 2Southwest Weather Consulting, LLC
IntroductionDigital stereo photgraphs collected during the T-REX field campaign are used to:● Develop algorithms for camera calibration, automatic feature matching, and reconstruction of 3D cloud scenes.
● Track the 3D path of cloud fragments at the upstream edge of rotor clouds and monitor their growth and dynamics until their merger with the main cloud.
Data
Camera calibration, feature matching, and 3D cloud reconstruction algorithms
Results: Statistics from 37 clouds
Conclusions
The T-REX field campaign took place in Owens Valley, CA, in the lee of the Sierra Nevada. ● IOP 6: March 25, 2006, 08:40-16:50 PST ● Cameras: Cannon 20D digital 8 Mpixel● Base line between cameras: 666m ● Shutter speed: ~10s
We study the evolution of cloud fragments which form upsteam of a largely stationary rotor cloud.
1. Lens distortion correction and image enhancement.
● Grubišić, V., and Coauthors, 2008: The Terrain-Induced Rotor Experiment: A field campaign overview including observational highlights. Bull. Amer. Meteor. Soc., 89, 1513–1533.
● Hu, J., A. Razdan, and J. A. Zehnder, 2009: Geometric calibration of digital cameras for 3D cumulus cloud measurements. J. Atmos. Oceanic Technol., 26, 200–214.
Algorithms have been developed for camera calibration, automatic feature matching, and reconstruction of 3D cloud scenes from stereo photographs. The resulting point clouds have:● high spatial resolution (~m) which is only limited by the pixel size and the distance to the cameras
● high temporal resolution (~10s)High resolution 3D point clouds allow detailed analysis of cloud evolution parameters such as growth, and horizontal and vertical movement.
2. Calibration of all six camera angles relative to each other by minimizing the distances (d) of “sightlines”.
3. Transformation of camera coordinate system (x, y, z) to world coordinate system (longitude, latitude, elevation) using real world reference point visible in both images.
5. Calculation of 3D coordinates of matched pixels via triangulation, and reconstruction of 3D point cloud.
4. Automatic matching of left and right image pixels of selected cloud feature.
Cameras
Sierra Nevada
Owens Valley
Camera A Camera B
Reference point Reference point
Reference pointImage from camera A Image from camera B Lon, lat, elev,
from Google Earth
d
Camera A Camera ACamera B Camera B
019 Jan22:00
20 Jan00:00
20 Jan02:00
20 Jan04:00
Time
0s 30s 70s
Image from camera A Image from camera B
-118.162
-118.160
-118.158
36.650
36.652
36.654
3800
4000
4200
4400
Latitude [°]
Long
itude
[°]
Elevation [m]
3800
4000
4400
4200
Ele
vatio
n [m
]-118.162 -118.160 -118.158
Longitude [°]
36.6
5436
.652
36.6
50
Latitude [°]
Sierra Nevada
Owens Valley
0s 10s 20s 30s 40s 50s 60s 70s
0
0.5
1
1.5
Hor
izon
tal t
rave
l dis
tanc
e [k
m]
0
50
150
250
Ele
vatio
n [m
]
100
200
0
0.2
0.6
0.8
Clo
ud a
rea
[km
2 ]
0.4
0s 10s 20s 30s 40s 50s 60s 70s
0s 10s 20s 30s 40s 50s 60s 70s
Hor
izon
tal s
peed
[m/s
]
0-10s 10-20s 20-30s 30-40s 40-50s 50-60s
0
10
20
30
40
-10
Ver
tical
spe
ed [
m/s
]
-5
0
5
10
0
0.5
1
1.5
Tra
vel d
ista
nce
of f
ront
and
bac
k ed
ge [
km]
Front
Back
0-10s 10-20s 20-30s 30-40s 40-50s 50-60s
0s 10s 20s 30s 40s 50s 60s 70s
Contact:[email protected]
