PLMR Calibration

Valerio ParuscioDr Jeff Walker

University of Melbourne

Outline

• Admissible error in brightness temperature measurement

• Available data for calibration

• Calibration options and recommendation

Model Sensitivity Assessment

How accurate has the Brightness Temperature measurement to be in order to have a Moisture content error less than 4%?

Hypothesis:• Roughness = 0.2• SS Albedo = 0.05• Soil Type = Silt clay loam

Variables:• Moisture Content (0.05-0.4) %v/%v• Vegetation Water Content (03)kg/m2

• Soil Temperature (280315)K• Incidence Angle (040)

Model Sensitivity Assessment

How accurate has the Brightness Temperature measurement to be in order to have a Moisture content error less than 4%?

Graphs Tb sensitivity

cold 4.5 3.2 6.8 7.3

hot 5.0 3.6 7.6 8.2

cold 2.2 1.3 3.4 2.9

hot 2.5 1.5 3.8 3.3

0 40 0 40

3 Vegeta

tion

Wate

r Conte

nt

dry wet

0

Moisture Content

Incidence Angle

Soil

Tem

pera

ture

cold 4.5 6.4 6.7 7.0

hot 5.0 7.2 7.6 7.9

cold 2.2 2.6 3.4 2.8

hot 2.5 2.9 3.8 3.2

0 40 0 40

Moisture Content

dry wet

Incidence Angle

Soil

Tem

per

atu

re 0

Veg

etati

on

Wate

r Conte

nt

3

1.3

2.2

H polarization

error (K)

V polarization

error (K)

Critical scenarios• High value of Vegetation Water Content• High Incidence Angle• Dry Soil

Max Tb error permitted =

Most common scenarios• Low value of Vegetation Water Content

Max Tb error permitted =

Commonly Tb error up to 8K can be tolerated

4.7K (Hpol)2.7K (Vpol)

2.2K (Hpol)1.3K (Vpol)

Available data for

calibration• Box pre and post flight

(~300K)

act

ual

measured

Available data for

calibration• Box pre and post flight

(~300K)

• Sky pre and post flight (~5K)

act

ual

measured

Box and Sky Brightness Temperature

Pre flight Box

Pre flight Sky Post flight Sky

Post flight Box

Available data for

calibration• Box pre and post flight

(~300K)

• Sky pre and post flight (~5K)

• Water in flight (~110K)

act

ual

measured

Temperature and Conductivity spatial series

Temperature and Conductivity time series

Transect–Buoy data comparision

Week 1 Week 2 Week 3 Week 4

Thermal Infrared data over the lake

Mon

Tue

Wed

Thu

Fri

Available data for

calibration• Box pre and post flight

(~300K)

• Sky pre and post flight (~5K)

• Water in flight (~110K)

• Sky in flight (~5K)

act

ual

measured

Available data for calibration

1. Box pre flight (~300K)

2. Sky pre flight (~5K)

3. Water in flight (~110K)

4. Sky in flight (~5K)

5. Box post flight (~300K)

6. Sky post flight (~5K)

act

ual

measured

Calibration options• 6 points (all)

• 4 points/2 points (box & sky from the ground)

• 3 points (box and water)

Calibration lines (6 beams, 2 polarizations)

Check the 4 pt calibration with water ponit

H polV pol

Check the 3 pt calibration with in flight sky ponit

V pol H pol

Variation in Tb measurement passing from the 4 points cal to

the 3 points cal

Time series of slope & offset (4 pts)

• From 4 pt

V-Pol

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

30/10/05 4/11/05 9/11/05 14/11/05 19/11/05 24/11/05 29/11/05

Date

Off

se

t (K

)

V3L

V2L

V1L

V1R

V2R

V3R

H-Pol

-40

-35

-30

-25

-20

-15

-10

-5

0

5

30/10/05 4/11/05 9/11/05 14/11/05 19/11/05 24/11/05 29/11/05

Date

Off

se

t (K

)

H3L

H2L

H1L

H1R

H2R

H3R

V-Pol

0.95

0.97

0.99

1.01

1.03

1.05

1.07

1.09

1.11

1.13

1.15

30/10/05 4/11/05 9/11/05 14/11/05 19/11/05 24/11/05 29/11/05

Date

Slo

pe

(K

/K)

V3L

V2L

V1L

V1R

V2R

V3R

H-Pol

0.95

0.97

0.99

1.01

1.03

1.05

1.07

1.09

1.11

1.13

1.15

30/10/05 4/11/05 9/11/05 14/11/05 19/11/05 24/11/05 29/11/05

Date

Slo

pe

(K

/K)

H3L

H2L

H1L

H1R

H2R

H3R

Variation in Tb measurement passing from the 4 points cal to

the 2 points cal

Error using a unique 4 pt calibration instead of a daily one

Conclusion

• Recommendation this campaign

V pol 4 pt dailyH pol 4 pt daily (or unique)

next campaign V pol 4 pt daily, 3 pt(?)

H pol 4 pt/2 pt daily (or unique)