Shane Bradt, PhD, GISP Kampala, Uganda | Sep 2014

Remote Sensing of Lakes

Part I: Basics

DRAFT

1.  Why use remote sensing for lakes?

2.  Remote sensing of lakes concepts

3.  Remote sensing of phytoplankton 3.

DRAFT

SDD = 0.9 m Chl = 39.4 µg l-1

TP = 46.3 µg l-1

SDD = 9.8 m Chl = 1.4 µg l-1

TP = 4.0 µg l-1

1

DRAFT

1

DRAFT

• Survey many lakes at once

• Have information for entire lake area

• Detect differences difficult to measure with other techniques

• Minimize data collection time and expense

• Collect repeated measurements over time

Benefits • Pixels may be too large for some lakes

• Imagery may not be available often enough

• Bands may not be specific to water quality parameters

• Can be very expensive

• Sensors see only a certain depth into the lake

Downfalls

1 Remote sensing for lakes

DRAFT

How lakes are different than land in RS 1

Very high Seldom used Very high

~20-150 nm Variability Classification For every image

Very low (<10%) Crucial Very low 10-25 nm Bio-optical Optical modeling For initial images, not every image

Intensity of RS signal Importance of atmospheric correction Importance of infrared Band width Analytical approach Analytical techniques Ground data necessary

Land Lakes

DRAFT

Chemical, Physical and Biological Activities

1. Light

2. Lake

3. Satellite

4. Data collection

Remote sensing of lakes concepts 2

DRAFT

Reflection

Scattering

?

2

DRAFT

Scattering

Absorption

Fluorescence

2

DRAFT

Reflectance = (at each wavelength)

(at each wavelength)

(at each wavelength)

R (λ) = Lw (λ)

Ed (λ, 0+)

2

Intensity of light leaving the water

Intensity of light entering the water

DRAFT

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

400 425 450 475 500 525 550 575 600 625 650 675 700 725

Wavelength (nm)

Rrs

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

0.0035

400 425 450 475 500 525 550 575 600 625 650 675 700 725

Wavelength (nm)

Rrs

SDD = 0.9 m Chl = 39.4 µg l-1

TP = 46.3 µg l-1

SDD = 9.8 m Chl = 1.4 µg l-1

TP = 4.0 µg l-1

3 Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

Remote sensing of phytoplankton

DRAFT

400 450 500 550 600 650 700 0

50

100

Wavelength (nm)

Ref

lect

ance

(%)

V B G Y O R

Chlorophyll a (ALL ALGAE) A

bsor

ptio

n

3 Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

DRAFT

400 450 500 550 600 650 700 0

50

100

Wavelength (nm)

Ref

lect

ance

(%)

V B G Y O R

Phycocyanin (CYANO) Abs

orpt

ion

3 Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

DRAFT

400 450 500 550 600 650 700 0

50

100

Wavelength (nm)

Ref

lect

ance

(%)

V B G Y O R

Rel

ativ

e ab

sorp

tion

Chl Chl

PC

3 Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

DRAFT

400 450 500 550 600 650 700 0

50

100

Wavelength (nm)

Ref

lect

ance

(%)

V B G Y O R

Rel

ativ

e re

flect

ance

3 Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

DRAFT

Scenedesmus and Microcystis

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

30

40

50

60

70

80

90

100

3 Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

DRAFT

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

400 425 450 475 500 525 550 575 600 625 650 675 700 725

Wavelength (nm)

Rrs

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

0.0035

400 425 450 475 500 525 550 575 600 625 650 675 700 725

Wavelength (nm)

Rrs

Phycocyanin Fluorescence

Low Abs. CDOM

Chlorophyll a

SDD = 0.9 m Chl = 39.4 µg l-1

TP = 46.3 µg l-1

SDD = 9.8 m Chl = 1.4 µg l-1

TP = 4.0 µg l-1

3 Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

DRAFT

Remote Sensing of Lakes

Part II:

Satellites

Shane Bradt, PhD, GISP Kampala, Uganda | Sep 2014 DRAFT

1.  Satellite sensors useful for lake RS

2.  Comparison of resolutions

3.  Deciding which sensor to use for lake RS 3.

DRAFT

Agency Purpose Satellite

Thematic Mapper NASA Land Landsat

SeaWiFS NASA Sea/Land OrbView-2

MERIS ESA Sea/Land Envisat

MODIS NASA Sea/Land Aqua & Terra

Satellite sensors useful for lake RS 1

Landsat TM

DRAFT

• Spatial •  Temporal • Spectral • Radiometric

Comparisons of resolutions 2

DRAFT

• Spatial – Size of smallest image element (pixel)

•  Temporal • Spectral • Radiometric

2

DRAFT

SPATIAL RESOLUTION

200 m

2

Landsat

MERIS

MODIS

SeaWiFS

DRAFT

• Spatial – Size of smallest image element (pixel)

•  Temporal – How often an image can be collected

• Spectral • Radiometric

2

DRAFT

TEMPORAL RESOLUTION

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

1

2

3

SeaWiFS

2

DRAFT

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

1

2

3

TEMPORAL RESOLUTIONSeaWiFS MODIS

2

DRAFT

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

1

2

3

TEMPORAL RESOLUTIONSeaWiFS MODIS MERIS

SeaWiFS

2

SeaWiFS MODIS

SeaWiFS

DRAFT

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

1

2

3

TEMPORAL RESOLUTIONSeaWiFS MODIS MERIS

SeaWiFS

Landsat

34 12 3 2

DRAFT

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

1

2

3

SeaWiFS MODIS MERIS

SeaWiFS

Landsat

34 12 3 TEMPORAL RESOLUTION19 9 2 2

DRAFT

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

1

2

3

SeaWiFS MODIS MERIS

SeaWiFS

Landsat

TEMPORAL RESOLUTION19 9 2 16 7 1 2

DRAFT

• Spatial – Size of smallest image element (pixel)

•  Temporal – How often an image can be collected

• Spectral – The locations and widths of “bands”

• Radiometric

2

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

2

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

Landsat TM

2

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

2

Landsat TM

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

SeaWiFS

2

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

2

SeaWiFS

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

MODIS

2

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

2

MODIS

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

MERIS

2

DRAFT

Microcystis aeruginosa - natural light

Wavelength (nm)

400 450 500 550 600 650 700

Ref

lect

ance

(%) w

hite

pan

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

2

MERIS

DRAFT

• Spatial – Size of smallest image element (pixel)

•  Temporal – How often an image can be collected

• Spectral – The locations and widths of “bands”

• Radiometric – Sensitivity of measurements

2

DRAFT

LEVELS

BITS 2

4

3

8

4

16

5

32

6

64

7

128

8

256

Imagine the sensor is a ruler to measure light…

…the better your ruler, the better you can measure!

DRAFT

LAKES 2

4

0 0

0

1 1

1 2

3 8

256

129 47

173

19

63

26

79

16 0 11

DRAFT

Bits Total

Levels “Lake” Levels

Landsat TM 8 256 26

SeaWiFS 10 1,024 102

MERIS 12 4,096 410

MODIS 12 4,096 410

2

DRAFT

250 meters 500 meters 1 kilometer B1: 620-670 nm B3: 459-479 nm B8: 405-420 nm B2: 841-876 nm B4: 545-565 nm B9: 438-448 nm B5: 1230-1250 nm B10: 483-493 nm B6: 1628-1652 nm B11: 526-536 nm B7: 2105-2155 nm B12: 546-556 nm B13: 662-672 nm B14: 673-683 nm B15: 743-753 nm B16: 862-877 nm B17: 890-920 nm B18: 931-941 nm B19: 915-965 nm B26: 1360-1390 nm

DRAFT

250 meters 500 meters 1 kilometer B1: 620-670 nm B3: 459-479 nm B8: 405-420 nm B2: 841-876 nm B4: 545-565 nm B9: 438-448 nm B5: 1230-1250 nm B10: 483-493 nm B6: 1628-1652 nm B11: 526-536 nm B7: 2105-2155 nm B12: 546-556 nm B13: 662-672 nm B14: 673-683 nm B15: 743-753 nm B16: 862-877 nm B17: 890-920 nm B18: 931-941 nm B19: 915-965 nm B26: 1360-1390 nm

Ocean Team

DRAFT

250 meters 500 meters 1 kilometer B1: 620-670 nm B3: 459-479 nm B8: 405-420 nm

B2: 841-876 nm B4: 545-565 nm B9: 438-448 nm

B5: 1230-1250 nm B10: 483-493 nm

B6: 1628-1652 nm B11: 526-536 nm

B7: 2105-2155 nm B12: 546-556 nm

B13: 662-672 nm

B14: 673-683 nm

B15: 743-753 nm

B16: 862-877 nm B17: 890-920 nm B18: 931-941 nm B19: 915-965 nm B26: 1360-1390 nm

Land Team

DRAFT