Presentation by Gennadii Donchyts (Deltares) at the Symposium Earth Observation and Data Science, during Delft Software Days - Edition 2017. Thursday, 2 November 2017, Delft.

1. Planetary-scale surface water detection
from space
Gennadii Donchyts

6. Donchyts et. al. 2016, http://nature.com/nclimate/journal/v6/n9/full/nclimate3111.html
http://aqua-monitor.appspot.com

7. New Land
New Water
Donchyts et. al. 2016, http://nature.com/nclimate/journal/v6/n9/full/nclimate3111.html
http://aqua-monitor.appspot.com

8. cloudsshadows
TOAreflectance,%
Percentiles, %
clear pixels
10% 62%

9. http://aqua-monitor.appspot.com
How did the Earth’s surface water
change over the past 30 years?

10. http://aqua-monitor.appspot.com
Aqua Monitor

11. Earth Engine
Storage and Compute
Landsat Satellite Data
Aqua Monitor: NASA Landsat and Google Earth Engine

12. 1. Annual surface reflectance percentile composites
2. Supervised classification (SVM)

14. Global Tide and Surge Model (GTSM) tidal range

15. Matching satellite overpasses and tides

16. The actual image (GMaps mosaic)

17. JRC water occurrence (30 years)

18. Water occurrence (2013-2017, min/max suppression)

19. Water occurrence, filtered

20. Reservoirs, ~150 000 mapped
http://bit.ly/global_reservoirs_map_2016
GRanD ~= 6000
N(t), A(t), V(t)

21. Prosser Creek Reservoir, USA
3 km

22. Prosser Creek Reservoir, USA
3 km

23. 0
500000
1000000
1500000
2000000
2500000
3000000
3500000
11/14/1984 5/7/1990 10/28/1995 4/19/2001 10/10/2006 4/1/2012 9/22/2017
Surface water area estimated from satellite and from local water level station
* after outlier removal
R² = 0.9903
0
500000
1000000
1500000
2000000
2500000
3000000
3500000
0 2000000 4000000
A* (A)
RMSE < 0.059 km2
A = 0.5 – 3 km2

24. t, x
λ
Sᵠ Sᶿ
Zs
Z
L
C
Cs
class
Y
ᵠ
z
clouds
land use classes
cloud shadows
azimuth
elevation
topography
hill shadows
Bayesian Network for Multispectral Optical Data

25. P(water | x, y, cloud=0)
2. Estimate probability density (prior)1. Detect water for cloud-free images
3. Estimate surface area using generative-discriminative algorithm
0. Input images from multiple sensors
~1200 images, <30m
𝑃 𝑊 𝑊 𝑡
=
𝑃 𝑊 𝑡
𝑊 ∙ 𝑃 𝑊
𝑃 𝑊 𝑡

30. Trends
Medium resolution, <30m

31. Number of Landsat images measured annually
1 50

32. Trends and challenges
Resolutions
Temporal: months to seconds
Spatial: 1km to 1m
Spectral: 3-15 bands
Radiometric: 8  16bit
Single sensor  Multisensor
Coverage
Local  Global
Volumes
100 MB  10 000 000 000 MB
Availability
~20PB of free satellite images

34. Questions?