LANDNET WG meeting #4CEOS/WGCV -41 Plenaryceos.org/document_management/Working_Groups/WGCV/Meetings/… · Jul.15 Aug.15 Sep.15 Okt.15 Nov.15 Dez.15 Jan.16 Feb.16 Mrz.16 Apr.16 Mai.16

www.aoe.cas.cn

Recent Progress of BaoTou Comprehensive

Cal&Val Site

September 5, 2016

LANDNET WG meeting #4 CEOS/WGCV-41 Plenary

Academy of Opto-Electronics(AOE), Chinese Academy of Sciences National Remote Sensing Center of China (NRSCC), Ministry of Science and Technology , P. R. China

Prof. Chuan-rong Li

报告时间9月5日下午17:00，时长15分钟（包含提问）。

www.aoe.cas.cn 2 2

Outline

(1) • Overview of the Baotou site

(2) • Progress in automatic calibration

(3) • Great events of Baotou site

www.aoe.cas.cn 3

Overview of the Baotou site

• Located in the Inner Mongolia, China; 50km away from the Baotou city.

• A flat area of approximately 300km2, about 1270m above sea level, features a cold semi-arid climate.

• Land covers: Sand, bare soil, grass, lake, various crops ( maize, sunflower, lucern, potato, etc. )

Lake Ulansuhai

3 grassland

Lake Ulansuhai bare soil

sand

sunflower lucern

potato maize

Site overview:

www.aoe.cas.cn 4

Stepwise Cal&Val technical system

Comprehensive surface targets

with artificial targets and natural

scenes reasonably matching

Airborne standard sensors

Ground test equipment

(a) artificial targets

Artificial portable

targets Artificial

permanent

targets

Natural

scenes

Data processing

and quality

evaluation system

Automatic

in-situ

calibration

system

Overview of the Baotou site

• Advanced Cal&Val system

• Great contribution to RS applications

• International platform for R&D

www.aoe.cas.cn 5

Accomplished automated surface spectrum measurement system

Progress in automatic calibration

As one of the four demonstration sites of the Radiometric Calibration Network (RadCalNet),

four automated systems with identical spectroradiometer configurations were set up on the

black, white and gray artificial permanent targets, and the sand field.

CE 318

1.5km

Automated system in sand field

Cimel CE318

Data

processing

server

Automated systems

Worldview3 image over Baotou site on Oct.

27, 2015. (Band 5/3/2)

www.aoe.cas.cn 6

Essential data collection by automated surface spectrum measurement system


Essential data of the site has been collected for several years.

Measuring the surface feature with high temporal resolution (2 min) from 8:30 to 16:30

local time, and supporting data self-checking and teletransmission.

0

5

10

15

20

25

30

35

Jul.15 Aug.15 Sep.15 Okt.15 Nov.15 Dez.15 Jan.16 Feb.16 Mrz.16 Apr.16 Mai.16 Jun.16 Jul.16 Aug.16

Black White Gray Sand

Month-year

No

. o

f d

ays w

ith

me

asu

rem

en

t

www.aoe.cas.cn 7

To meet the requirement of RadCalNet portal, the surface reflectance is retrieved from the

observed reflected radiance and the measured atmospheric parameters, with the help of

atmospheric radiative transfer model (MODTRAN);

Automated system only observes surface at fixed point. Because of the heterogeneity of the

target, the reflectance should be corrected according to the historical surface measurement.


400 500 600 700 800 900 10000

0.2

0.4

0.6

0.8

Wavelength (nm)

Su

rfac

e re

flec

tan

ce

Measured (SVC)

Retrieved (Auto system)

400 500 600 700 800 900 10000

0.2

0.4

0.6

0.8

Wavelength(nm)

Su

rfac

e re

flec

tan

ce

Measured (SVC)


400 500 600 700 800 900 10000

0.2

0.4

0.6

0.8

Wavelenth(nm)

Su

rfac

e re

flec

tan

ce

Measured (SVC)


400 500 600 700 800 900 10000

0.2

0.4

0.6

0.8

Wavelength (nm)

Su

rfac

e re

flec

tan

ce

Measured (SVC)

Retrieved (Auto system)Black White

Gray Sand

Fixed point (green curves) V.S.

Area average (red curves)

scat

sky

diffuse

sky

direct

solar

g

EEE

L

Direct irradiance Sky irradiance

Observed at-ground

reflected radiance

Calculated with MODTRAN and

atmospheric parameters (AOT, water

vapour, …)

*S

Fix point reflectance

Scaling coefficient

Fix

ed

po

int

reflecta

nce r

etr

ieval

Sp

atia

l sca

ling

effe

ct co

rre

ctio

n

www.aoe.cas.cn 8

84 effective files following RadCalNet portal format have been generated and uploaded.

Each file contains information for one day of one target. In the file, there are 13 records for

observations at different time (9:00-15:00 local time, 2 values/hour).


0 096 098 099 101 103 104 107 111 112 113 115 119 127 128 129 130 131 133 175 176 204 210 211 213 214 215 216 217 218 222 2230

0.02

0.04

0.06

0.08

0.1

DOY

Ref

lect

ance

Blue Green Red NIR

0 096 098 099 101 103 104 107 111 112 113 115 119 127 128 129 130 131 133 175 176 204 210 211 213 214 215 216 217 218 222 2230

0.05

0.1

0.15

0.2

0.25

DOY

Ref

lect

ance

Blue Green Red NIR

0 096 098 099 101 103 104 107 111 112 113 115 119 127 128 129 130 131 133 175 176 204 2380

0.2

0.4

0.6

0.8

DOY

Ref

lect

ance

Blue Green Red NIR

Bla

ck ta

rge

t G

ray ta

rge

t W

hite

ta

rge

t

www.aoe.cas.cn 9

BRDF characteristics


400 600 800 1000 1200-40

-20

0

20

40

60

Wavelength(nm)

Fanis

tro

py(%

)

-30° -20° -10° 10° 20° 30°

400 600 800 1000 1200-40

-20

0

20

40

60

Wavelength(nm)

Fanis

tro

py(%

)

-30° -20° -10° 10° 20° 30°

400 600 800 1000 1200-40

-20

0

20

40

60

Wavelength(nm)

Fanis

tro

py(%

)

-30° -20° -10° 10° 20° 30°

Black white

gray

400 500 600 700 800 900 1000 1100 1200-20

-10

0

10

20

30

40

Wavelength(nm)

Fa

nis

otr

op

y(%

)

30o

20o

10o

-10o

-20o

-30o

sand

The artificial targets, which are paved by gravels, have much more obvious angular

anisotropy than the sand field.

With Ross-Li model, the BRDF effects can be well described. Therefore, after BRDF

correction, the accuracy of calibration can be improved.

• Black target: 0.24%(<10°);

0.46%(<30°)

• Gray target: 0.67%(<10°);

0.74%(<30°)

• White target: 0.95%(<10°);

2.03%(<30°)

• Sand target: 0.478%(<10°);

0.692%(<30°)

RMSE of BRDF model

With BRDF correction, the

angular effects may be reduced

below 1% in most cases.

www.aoe.cas.cn 10


The spectroradiometers used in the automated surface spectrum

measurement system were calibrated in NIM (National Institute

of Metrology, China).

The overall uncertainty is reported to be lower than 2%. (k=1,

traced to NIM).

400 500 600 700 800 900 10000

0.5

1

1.5

2

2.5

Wave length (nm)

Sta

bili

ty (

%)

Black

Gray

White

SandBlack: 0.13%

Gray: 0.12%

White: 0.11%

Sand: 0.1%

400 500 600 700 800 900 10001

1.5

2

2.5

3

Wave length (nm)

Co

mb

ine

d U

nce

rta

inty

(%

)

Black

Gray

White

Sand

Overall uncertainty of 4 spectroradiometers

Wavelength/nm 300 400 500 600 700 800 900 1000

Repeatability/% 1 0.7 0.5 0.5 0.5 0.5 0.6 0.8

Lamp/% 0.8 0.6 0.4 0.4 0.4 0.4 0.5 0.6

Current % 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

Alignment for lamp/% 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Distance % 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

Diffuser pannel/% 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

Uniformity /% 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Alignment for

spectrometer/% 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

nonlinearity % 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Stray light /% 0.8 0.7 0.5 0.5 0.5 0.5 0.5 0.6

Combined U/%(k=1) 1.84 1.56 1.32 1.32 1.32 1.32 1.4 1.57

Expanded U/% (k=2) 3.7 3.1 2.6 2.6 2.6 2.6 2.8 3.1

Uncertainty budget for lamp-panel system (NIM)

Stability of 4 spectroradiometers

www.aoe.cas.cn 11

Demonstration on satellite calibration

Since the end of February 2016, when all the 4 systems at artificial targets and sand field were

updated with same spectroradiometers，there have been 10 matchups for Landsat8, Sentinel-

2a, ZY3, ZY-02C, GF-1, GF-2 and CBERS-4 satellites.

GF1 (Pan:2m / MUX:8m)

Acquired date: 2016-06-07

GF2 (Pan:1m / MUX:4m)


ZY02C (Pan:5m / MUX:10m)


CEBRS04 (Pan:5m / MUX:10m)


ZY3 (Pan:2.1m / MUX:6m)

Acquired date: 2016-04-20 Landsat 8 (Pan:15m / MUX:30m)


Satellite Date

Landsat8 04/21,05/07,06/08,06/

24

07/26,08/04,08/27

Sentinel-

2a

03/30, 04/29, 07/21

CBERS-4 06/07

GF-1 04/23,06/07,08/20

GF-2 04/22

ZY3 04/20

ZY3-02 07/20

ZY-02C 04/16,04/19,04/22,04/

25,04/28,05/12,

06/07

www.aoe.cas.cn 12


Demonstration satellite in RadCalNet framework

Average differences between simulated TOA radiance and observed TOA

radiance are 4.8%, 1.5%, 0.0%, 1.2% for Blue, Green, Red, NIR band of

OLI/Landsat8.

Blue Green Red NIR0.8

0.9

1.0

1.1

1.2

Channels

Sim

ula

ted

/Ob

serv

ed

2016-04-21

2016-05-07

2016-06-08

2016-06-24

Clear day but large AOD (0.6389@550nm)

2016/04/21 2016/05/07 2016/06/08 2016/06/240

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Date

Atm

osp

heri

c p

ara

mete

rs

Aerosol optical thickness@550nm

Columnar water vapor(g/cm2)

Except for 8 Jun, AODs at

other days are smaller than

0.3@550nm

OLI/Landsat8 image

www.aoe.cas.cn 13


Chinese high-resolution satellite---ZY3-02

Pan+MSS/ZY3-02

Pan/ B1 B2 B3 B4

Wavelength

(um) 0.5~0.8

0.45~

0.52

0.52~

0.59

0.63~

0.69

0.77~0

.89

Pixel size

(m)

2.1(NAD);

3.5

(FWD/B

WC)

6

swath width

(km) 51 51

revisit

period

(±32°,day

s)

5 5

ZY3-02 satellite was launched on May 30, 2016, which is a new civilian high-resolution

mapping satellite. It will join its predecessor ZY3-01 satellite (launched in 2012) in the same

orbit to form a network and capture high-definition, 3D images and multispectral data.

The on-orbit test was carried out over the Baotou site during July 15-25, 2016.

www.aoe.cas.cn 14

• Measurement Synchronous measurement: spectral reflectance for 3 permanent artificial targets and 6

portable targets; Automatic measurement: spectral radiance for 3 permanent artificial targets and the sand

field; atmospheric parameters.



portable gray-scale targets Portable colored targets

AOD atmospheric profiles sunphotometer atmospheric sounding

synchronous spectrum measurement

www.aoe.cas.cn 15


Chinese high-resolution satellite---ZY3-02 Chinese high-resolution satellite---ZY3-02

Radiometric calibration

• The portable target of 60% reflectance shows saturation in

the blue band image, so the corresponding point was

removed when fitting calibration coefficient.

• Using 2 portable colored targets to validate calibration result

based on 4 automated measurement systems, as well as

calibration result based on all targets’ synchronous

measurement. Further Improvement is still necessary for

automated calibration mode.

The response linearity were greater than 0.98 for all bands . Validation results by using portal blue colored targets

For saturation, the DN

value of red region is

filled with 977 by

satellite agency

Automatic measurements/

Synchronous measurements

Targets

reflectance

Simulated

targets TOA

radiance

Observed

targets

DN

calibration coefficients:

a(automated mode);

b(Synchronous mode)

Sensors

Sensors

Observed

targets DN

Observed TOA

radiance using

coefficients a/b

Simulated

sand TOA

radiance

Validation Calibration

Measurements on

colored targets

Targets

reflectance

www.aoe.cas.cn 16



Calculation Specification

Cross track 0.153

0.1 Along track 0.103

MTF

edge angle SNR MTF-ref Mean of relative

errors（100 times） RMSE

（100 times） Error ＜10% （100 times）

-8.7610° 42 0.15 -0.83% 20.76% 38

Error analysis results for 100 simulated images

Estimate errors of 100 simulated images

The error analysis indicates that

influenced by factors such as

black/white contrast, atmosphere

and sensor noise, the SNR value

when estimating MTF is only 42,

and in addition the edge angle is

larger than the recommended

threshold 5°, so the current MTF

evaluation may contain relatively

no small uncertainty. -6,00%

-5,00%

-4,00%

-3,00%

-2,00%

-1,00%

0,00%

1,00%

2,00%

0 1 2 3 4 5 6 7 8 9 10

Re

lati

ve

err

or

Edge angle

Relative estimate errors for different angles

www.aoe.cas.cn 17

In August 2016, the first workshop of the “National Calibration and Validation Site

for High Resolution Remote Sensors” was held at Baotou. Representatives of all

EO satellite operational agencies of China attended the workshop.

Great Events

www.aoe.cas.cn 18

The 28th IVOS meeting and the 5th RadCalNet meeting were hosted by Baotou site during July

18 to 21 2016. Nearly 30 worldwide scientists from NASA, NOAA, ESA, CNES, DLR, NPL,

CSIRO, ONERA, GSJ, SDSU, etc, attended this meeting.

Great Events

www.aoe.cas.cn 19

After this meeting, on July 22, four scientists (Dr. Steffen Dransfeld from ESA, Dr.

Françoise Viallefont-Robinet from ONERA, Dr. Esad Micijevic from USGS and Dr.

Hirkazu Yamamoto from GSJ) visited the Baotou site.

Great Events

www.aoe.cas.cn

20

Future work

To improve the operational capability

Robust our system in operational running, especially the improvement of controlling

and data processing software.

Extension of spectrum range to SWIR domain.

To improve the calibration accuracy

Development of the local atmospheric model：Explore the information from historical data to find the characteristics of the local atmosphere and surface. Study how to improve or correct the atmospheric radiative transfer model.

Development of automated measurement device for total/diffused sky irradiance, providing observed total irradiance to replace the simulation value derived from MODTRAN in current system.

www.aoe.cas.cn 21

To Enhance the capability of land product validation based on the infrastructure of Baotou Site

crop (maize, wheat, sunflower, melon)

Future work

Install evaporation, soil moisture observation equipment of Eddy covariance system (EC), Large aperture scintillometer (LAS) and TDRs, to realize the supporting capacity of land surface product modeling and validation;

Study on the temporal, spatial, spectral and viewing angle matching technologies, decreasing significant scaling bias of step-wised validation.

Eddy covariance system (EC)

Large aperture scintillometer (LAS)

MiniTrase COSMOS

Detector ESU of 30m×30m

Soil moisture profile

The distributed

soil moisture

monitoring

system

4D observation

platform

The matrix evaporation

observation system

grass

www.aoe.cas.cn 22

Activities on Baotou site

Documents

LANDNET WG meeting #4CEOS/WGCV -41 Plenaryceos.org/document_management/Working_Groups/WGCV/Meetings/… · Jul.15 Aug.15 Sep.15 Okt.15 Nov.15 Dez.15 Jan.16 Feb.16 Mrz.16 Apr.16 Mai.16