1. Mapping Vegetation with Synthetic Aperture Radar:
Applications in Kenya and Southeast Asia
Thomas Ballatore, Ph.D., GISP
Director, Lake Basin Action Network
Faculty Aide, Center for Geographic Analysis, Harvard University
ABCD-GIS Seminar Series
07 December 2016
K450 CGIS Knafel

2. Remote sensing is…
the practice of deriving information about the Earth’s land and water surfaces using images acquired from an overhead perspective, by employing electromagnetic radiation in one or more regions of the electromagnetic spectrum, reflected or emitted from the Earth’s surface.
Campbell and Wynne
Introduction to Remote Sensing
p.6, 5th ed. (2011)

3. Remote sensing is…
the practice of deriving information about the Earth’s land and water surfaces using images acquired from an overhead perspective, by employing electromagnetic radiation in one or more regions of the electromagnetic spectrum, reflected or emitted from the Earth’s surface.
Campbell and Wynne
Introduction to Remote Sensing
p.6, 5th ed. (2011)

4. The Electromagnetic Spectrum
CC BY-SA 3.0,

5. Sensing in the Visible and NIR

6. SPECTRAL
Landsat OLI
Soil
Green
Dry
Soil
Dry
Green

7. The Problem with Clouds…

8. Remote sensing is…
the practice of deriving information about the Earth’s land and water surfaces using images acquired from an overhead perspective, by employing electromagnetic radiation in one or more regions of the electromagnetic spectrum, reflected or emitted from the Earth’s surface.
Campbell and Wynne
Introduction to Remote Sensing
p.6, 5th ed. (2011)

9. Remote sensing is…
the practice of deriving information about the Earth’s land and water surfaces using images acquired from an overhead perspective, by employing electromagnetic radiation in one or more regions of the electromagnetic spectrum, reflected or emitted from the Earth’s surface.
Campbell and Wynne
Introduction to Remote Sensing
p.6, 5th ed. (2011)

10. The Electromagnetic Spectrum
CC BY-SA 3.0,

11. Types of Sensors Visible & Reflected IR Thermal IR Microwave
Remote Sensing
Thermal IR
Remote Sensing
Microwave
Remote Sensing
Radiation
Source >>
Object >>
Type >>
Sun Object Object Sensor
Reflecting Radiating Radiating Reflecting
Passive Passive Passive Active
Spectral
Radiance >>
© Asian Institute of Technology, 2014, All Rights Reserved

12. Microwave Radiation
10GHz
1GHz
0.2μm
1.0μm
10μm
1mm
10mm
10cm 1m
Visible
Microwave Bands
Middle
infra-red
Thermal
infra-red Ka Ku X C S L P UV
Near infra-red
The electromagnetic spectrum
(after NASA/JPL, 1988)
100
Transmittance (%) 50
0.2 μm
1.0μm
10μm
1mm
10nm
10cm 1m
Wavelength
X, C, S, L bands are used for SAR on-board satellites
Characteristic of atmospheric spectral transmittance
(after NASA/JPL, 1988)
© Remote Sensing Technology Center of Japan, 2014, All Rights Reserved

13. Surface scatter (Reflection) mechanism
lake
grass
forest
©METI/JAXA
© Remote Sensing Technology Center of Japan, 2014, All Rights Reserved

14. Backscatter change in a paddy field
Open water
Planting
Vegetated
weak
strong
HH backscattering

15. Seasonal change
Seasonal changes in microwave backscatter provide useful information to detect paddy field area.
SAR Backscatter
Low
High

16. Sentinel 1A
11 Aug 2015
Innundated paddies are dark

17. Sentinel 1A
22 Oct 2015
After growing and/or harvest, more backscatter. The river, however, has flooded!

18. Asian Development Bank (ADB) MOOC

21. Tana River Basin, Kenya

23. Example case of area around Bura Irrigation Project

24. Sentinel 2A
22 Jan 2016
Healthy, growing vegetation is in red. If all images were this quality, the classification would be easy. The pixel size is 15m.

25. The problem with clouds…

26. Landsat 8 OLI
10 Jan 2016

27. Landsat 8 OLI
26 Jan 2016

28. Landsat 8 OLI
11 Feb 2016

29. Landsat 8 OLI
27 Feb 2016

30. Landsat 8 OLI
14 Mar 2016

31. Landsat 8 OLI
30 Mar 2016

32. Landsat 8 OLI
15 Apr 2016

33. Landsat 8 OLI
01 May 2016

34. Landsat 8 OLI
17 May 2016

35. Landsat 8 OLI
02 Jun 2016

36. Landsat 8 OLI
18 Jun 2016

37. Landsat 8 OLI
04 Jul 2016

38. Only 1 out of 11 Landsat 8 OLI images are usable for the current year!
For Sentinel 2A, there are only 2 usable images…

39. The solution is to use active microwave sensors (SAR) that can see through clouds!

40. Sentinel 1A
17 Jan 2016
Healthy vegetation is bright. Resolution is nominally 10m but despeckling reduces that a bit.

41. Sentinel 1A
05 Mar 2016

42. Sentinel 1A
29 Mar 2016

43. Sentinel 1A
22 Apr 2016

44. Sentinel 1A
16 May 2016

45. Sentinel 1A
09 Jun 2016

46. Sentinel 1A
03 Jul 2016

47. Sentinel 1A
20 Aug 2016

48. Sentinel 1A
13 Sep 2016

49. Spatial Resolution: Landsat 8 OLI vs. Sentinel 2A vs. Sentinel 1A

50. Landsat 8 OLI
04 Jul 2016

51. Sentinel 2A
30 Jun 2016

52. Sentinel 1A
03 Jul 2016

53. A close-up of the river vegetation

54. Landsat 8 OLI
04 Jul 2016
Landsat is good but the 30m resolution loses to Sentinel 2A on the next slide.

55. Sentinel 2A
30 Jun 2016

56. Sentinel 1A
03 Jul 2016
Sentinel 1 is not as good as Sentinel 2 because it has much less spectral resolution, however, given the prevalence of clouds, it is a great resource.

57. Acquiring SAR data

58. Processing SAR data

59. For questions and/or comments, please write: ballatore@g.harvard.edu