Spectrum Earth
Targeting GEO’s Needs, Integrating Multi-source Data,
and Lowering Barriers of Application
Speaker：Yan Liu
Team Member：Xingfa Gu、Juan Li、Yulin Zhan、Xiangzhi Huang、Xiangqin Wei、
Xiaofei Mi、Miao Liu、Hu Zhang、Xingeng Dong、Yongtao Jin

Content

1. Working Experience with GEO
2. GEO’s Goals and Vision
3. Features and Advantages of Spectrum Earth
4. Progress of China GEO Cooperation Initiative2

Working Experience with GEO
Assist leaders to participate
GEO events

Participate in organizing GEO
and AOGEO events

S&T exchanges

GEO plenaries, ExCom meetings,
PB meetings

3 AOGEO Workshops and 1 joint side
event with EuroGEO

AOGEO Training Workshop, Youth
Track in 2021 GEO week, etc

International Communication Platform

S&T communication with world top experts;

Multi-stakeholders communication platform

Scientific research address actual needs.

3

GEO’s Goals and Vision
Data Providers

Earth Observations
Satellites

Research Teams
Organizations
Institutions……

Research Teams

Spectrum information is
the fundament of
accurate quantitative
inversion.

GEO Engagement
Priorities

The Earth Surface
Parameters
LAI

Model Inversion
Drones

Decision Makers

Albedo……

存在的一些问题

LandcoverIn-situetc

4Features and Advantages of Spectrum Earth

1

2

3

4

Natural
Earth

Image
Earth

Spectrum
Earth

Knowledge
Earth• Objective Existence• Directly Shot by• Natural and Artificial Objects Remote Sensing

 Comprehensive: Multispectral, multiscale,temporal continuous satellite observed
spectrum data of the earth's surface; Quantitative: Standard radiation, space, time ofthe earth's surface; Continuous: Full coverage, continuous time,
spectral normalization.

• Information-Knowledge• Multi-level integration

GEO Engagement
Priorities

存在的一些问题

Spectrum is theunique “fingerprint”
of land surface andcore information thatsatellite can capture5Features and Advantages of Spectrum Earth
Ideal Spectrum Earth：Full and continues information in
multiple dimensions

3
Spectrum Earth

SpatialDimensionServes applications that needs
different spatial details

TemporalDimension

Meet the needs of observing
changes in different time
periods.

SpectralDimension

Fully reflect spectrum details.

Observation Angle
Dimension

Supportenergybalance,surface structure analysis.

6Features and Advantages of Spectrum Earth
Reality: A single satellite or sensor can realize near-completeness ina certain dimension.
SpatialDimension

TemporalDimension

SpectralDimension

Drones,Commercial
Satellites

Land
Satellites

On Demand

Week-Month

Hyperspectral,
spectrometer

Multispectral

Observation
Multi-angle
Angle’s Dimension

Wide

Meteorological
Satellites

Day

Microwave

Narrow Wide7

Features and Advantages of Spectrum Earth➢ The ideal spectral earth is a complex and huge scientific research andengineering system, which is difficult to realize in short time.

➢ Seek a suitable start for technical research and system development.
– Pressing needs in local and international community, especially in GEO.
– Enough satellite data.
– On a certain technical basis.
➢ Gradually realize the multi-dimensional integrity and continuity of land
surface spectrum information.

8

Features and Advantages of Spectrum Earth
Global environmental problems are becoming increasingly prominent, while low-resolution
data is difficult to satisfy demands.
Typical Problems: Climate Change， ozone layer destruction, biodiversity reduction, acid rain spread, forest
loss, land desertification, air pollution, water pollution, marine pollution, solid waste pollution.

MODIS（500m）

Sentinel-2（10m）

Since low-resolution data cannot capture the detailed changes of the surface, mediumresolution data is urgently needed to provide information support!
9Features and Advantages of Spectrum EarthG l o ba l e ar t h o b se r vat i o n h as e n te re d t h e e r a of m e d i u m - re s o l u t i o n e r a .
At present, there are more than 20 medium-resolution
Seriessatellites in orbit around the world.

ZY Satellites

Gaofen Series Satellites

Sentinel Satellites

Gaofen WFV Satellite
Data Coverage Map

Satellite

Country

Ziyuan Series

ZY 02C/D
ZY 04

China

Gaofen Series

GF-1A/B/C/D
GF-3/4/6

China

Domestic
commercial
satellite series

beijing-1
Jilin-1

China

LandSatLandSat-8

America

Sentinel Series

Sentinel-2A/B

SPOT Series

SPOT-6…

EU
FranceThere are numerous types and large quantities of medium-resolution satellite data, difficult in processing
and short of global spatiotemporally continuous medium-resolution data product set, which cannot meet10
the needs of fine monitoring of the global environment.

Features and Advantages of Spectrum EarthD e ve l o p i n g Sp e c t r u m Ear t h to i m p ro ve
gl o ba l d at a e f f i c i e n c y
The medium-resolution data of Gaofen series has developed anefficient global coverage capability. In November 2019, CNSA
announced open sharing of China’s Gaofen data with 16-meter
resolution.

Improve thelevel ofapplication
technology
东西纬度oImprove global/
large-scalemonitoring
capabilities

Gaofen, Landsat and Sentinel 2 series satellites.

o

o

o

o

Improve multitemporalmonitoring
capabilities

P6,P29 P7,P29 P8,P29

P11,P26
P10,P25P11,P25

o

70

东西经度

P9,P24 P10,P24P11,P24

南
北
纬
度

14,35
13,34
12,33
11,32
10,31

常规经纬网格中低纬度
地区

9,6 9,7 9,8 9,9 9,10 9,11 9,12 9,13 9,14 9,15 9,16 9,17 9,18 9,19 9,20 9,21 9,22 9,23 9,24 9,25 9,26 9,27 9,28 9,29 9,30
8,5
7,4
6,3
5,2
4,1
3,0

P9,P11 P10,P11P11,P11

o-70

P10,P10P11,P10o

沿0 度经线逆时针旋
转90 度的经纬网格

medium-resolution remote sensing data resources including

o

o
o

高纬度地区

Spectrum Earth is most suitable for taking advantage ofo-30 -20 -10 0 10 20 30
120

南 110 P6,P28 P7,P28
北 100o P6,P27
P8,P27
经 90o
P9,P26
度 80o

高纬度地区

南 -80
P9,P9
北 -90o P6,P8 P8,P8
经 -100oP6,P7 P7,P7
度 -110o-120

oP11,P9

P6,P6 P7,P6 P8,P6

o

o

o

o

o

o

o

-30 -20 -10 0 10 20 30

东西纬度

Improve multisource dataprocessing andapplication
capabilities

11Features and Advantages of Spectrum Earth
Seek a suitable start for technical research and system development
Mediumresolution……
Landsat Series

Gaofen Series

Sentinel Satellite

Multispectrum

Spatiotemporalcontinuity

补个图

12

Features and Advantages of Spectrum EarthSome

ProblemsintheApplication of GEO Worldwide•

Solutions Put forward by Several Countries

Large-scale

Many types of loads and large differences in•Focusing on solving geometric problems

application accuracy;•

High threshold for back-end users’ application.

Some

Problems

in

the

•

The value of overseas application needs to be
improved;•

Connection with international technology systemneeds to be improved.

•

Globalized

Application of Gaofen data

Optical Data Centre（ODC，Australia)
Analysis Ready Data（ARD，CEOS)
Single-load data product，application- oriented

Spectrum Earth（ SE，China）
Focusing on solving problems such as multi-load,
multi-temporal and massive data••

Data Information system （DAIS）
Information and product production

Spectrum Earth was proposed in "China’s Plan for Implementing GEOSS (2016-2025)"
13

Progress of China GEO Cooperation Initiative
Research on Development of Medium Spatial Resolutionof Spectrum Earth and its Application Technology
Dec 1st, 2020- Dec 1st, 2023
Key R&D Program of the Ministry of Science and Technology
Key projects of intergovernmental scientific and technological innovation cooperation
Overseas Cooperation Teams: Geoscience Australia

International Centre for integrated Mountain Development

Research Areas：Australia, Nepal, France, Cambodia–Taking into account both ecosystem diversity and GEO activity
Research Tasks: 1. Multispectral Data Processing Technology System of Spectrum Earth;
2. Expanding Technology from Multispectral Images to Hyperspectral Images;
3. Research and Development of 10-meter level Spectrum Earth platform;
4. Application and Demonstration based on Spectrum Earth.
14

Progress of China GEO Cooperation Initiative
Challenges

Basic
Situation

FacingChallenges•

Cloudy and snowy, highrequirements for cloud andsnow recognition accuracy;•

Difficult to obtain effective
observations at any scale
during the rainy season;•

Parts of the region most of
the time are covered byclouds or thick aerosols;• High Altitude• Complex Terrain• Monsoon Climate

15

Progress of China GEO Cooperation Initiative
I n c o r p o r at i n g l o w - re so l u t i o n i n f o r m a t i o n i n to s u r f a c e re f l e c t a n c e
a n g l e n o r m al i z at i o n .

Existing
Problems

Solutions

1. The GF-1 wide-field imager has a larger field ofview, but its multi-angle observation capability
cannot fully describe the anisotropic reflection
characteristics of the surface.

2. There are many factors affecting the anisotropic
reflection characteristics, and the reflection anisotropy
characteristics of different structures of the surface arequite different.

The low-resolution surface reflection anisotropy feature product is introduced to analyze the
distribution characteristics of the anisotropic reflection feature, extract the prior knowledge ofthe surface anisotropic reflection, and realize the angle normalization of the reflectance data of
the GF-1 wide-field imager.
Achieving consistency and comparability of observational angles of data16

Progress of China GEO Cooperation Initiative
I n c o r p o r at i n g l o w - re so l u t i o n i n f o r m a t i o n i n to s u r f a c e re f l e c t a n c e
an gl e n o r m al i z at i o n .
Algorithm
Scheme1. Kernel driver model parameternormalization

2. The extraction of prior BRDF knowledge

The normalized BRDF is more regular,
which facilitates the extraction of priorknowledge

1. Applicability evaluation of prior BRDF

Results
Evaluation

The extracted prior BRDF canrepresent most pixels’
anisotropic reflection features.
Prior knowledge changes
significantly over time.

Angle normalization is performed bysimulating the relationship between
directional reflectance and real
observations

2. Normalized evaluation of GF1-WFV reflectance

校
正后

Simulation data validation showed that the prior
BRDF had a good correction effect on the GF-1
WFV observation plane (RMSE<0.02).

3. Angle normalization

校
正
前

%

The reflectance before and after normalization is significantly different, andthe maximum relative difference can reach 16%. The reflectance after
normalization has a high consistency with that of Landsat (NIR RMSE<0.056). 17

Progress of China GEO Cooperation Initiative
Re c o n st r u c t i o n of m o n t h l y re f l e c t an c e d a t a i n c l o u d y a n d r a i n y re g i o n s
Lack of spatiotemporal continuous
low-resolution reflectanceproducts to assist in data
reconstruction••

The limited 10-meter-level clear sky data isdifficult to meet the input requirements oftraditional data fusion algorithms.
Affected by the thick aerosol in the mountains, it
is impossible to use the cloud mask data torealize automatic screening of clear sky data.

Commonly used data
reconstruction methods operate
independently on a single band,
but lack consideration of thecorrelation between multiple bands

Problems

February 2020, black represents missing data

NBAR is one of the most widelyused reflectance products, often
used as auxiliary data for
Solutions medium-resolution scale data
reconstruction.
• Synergistic use of angularreflectance and NBAR toimprove the available data in
the reconstruction algorithm,
and taking into account surface
time changes, quantitatively
imputation for missing data.
•

Some areas of Nepal, all observations of Gaofen 1 in January 2020,
black represents missing data••

Using pixels’ time series changes in the wholegrowing season to reconstruct data from thetime dimension, realize the reconstruction of
spatiotemporal continuous data over a long
period of time
Compare the 10-meter-level data with the lowresolution time curve, and remove the thickaerosol data through outlier analysis.

Aiming at the characteristics ofmainly vegetation coverage in
Nepal, the vegetation index is used
as a unified index to search forsimilar pixels in the spatiotemporalwindow to achieve multi-band
collaborative reconstruction.

18

Progress of China GEO Cooperation Initiative
Re c o n st r u c t i o n of m o n t h l y re f l e c t an c e d a t a i n c l o u d y a n d r a i n y re g i o n s

Medium Resolution Scale•

Effectively filling in missing clear
sky data.

•

With time series information, theeffect of thick aerosols onreflectance is mitigated.

•

The accuracy is close to that of
traditional data fusion algorithms（Pearson’s r~0.95, RMSE ~0.04）•

There is no need to manually filter
input data, enabling automatedprocessing of large areas•

In areas with long-term cloud
coverage caused by terrain, thealgorithm needs to be further
improved.

Jan.

Feb.

Mar.

Apr.

May

Jun.

Jul.

Aug.

Sept.

Oct.

Nov.

Dec.

The best monthly observations of the Gaofen-1 satellite in 2020

Jan.

Feb.

Mar.

Apr.

May

Jun.

Jul.

Aug.

Sept.

Oct.

Nov.

Dec.

Monthly reflectance after reconstruction in 2020

19

Progress of China GEO Cooperation Initiative
Ap p l i cat i o n D e mo n st rat i o n of Eco l o gi cal En vi ro n me n t f acto r s Mo n i to r i n g
Based on the spectrum earth data, using the self-developed LAI inversion algorithm (R2=0.818, RMSE=0.5) coupledwith the PROSAIL radiative transmission model and the neural network model, the application demonstration of
the leaf area index, a typical element of the ecological environment, was carried out in the whole area of Nepal.

Algorithm Accuracy Verification

Spatial distribution of LAI of typical elements of the ecologicalenvironment in Nepal in 2020

20

Progress of China GEO Cooperation Initiative
Ap p l i cat i o n D e mo n st rat i o n of Eco l o gi cal En vi ro n me n t f acto r s Mo n i to r i n g
Based on the spectrum earth data and the self-developed FVC inversion algorithm based on the pixel dichotomy
model (R2=0.827, RMSE=0.086), an application demonstration of typical ecological environment elementsvegetation coverage was carried out in Nepal.

Algorithm Accuracy Verification

Spatial distribution of vegetation coverage of typical elements ofthe ecological environment in Nepal in 202021

Progress of China GEO Cooperation Initiative
Ap p l i cat i o n D e mo n st rat i o n of Lan d Co ve r Mo n i to r i n g
Optimize the deep learning Unet model and establish the loss function of the inverse log-weighted
cross-entropy of the type percentage.

2016

The random sampling method is usedfor verification, and the classification
accuracy is about 84%.

22

Progress of China GEO Cooperation Initiative
m u l t i s p e c t r al i m age s to h y p e r sp e c t r al i m a g e s➢ Targeting the characteristicsof the ground objects in thedemonstration area, thespectrum information of
typical ground objects,
especially the mineral
spectrum data, was collected,
which provided data support
for the expansion of
hyperspectral images.
➢ The construction of thespectrum database of typicalground objects oriented tothe target load is completed,which provides databasesupport for the engineeringof hyperspectral image
expansion.

Measurement
Type

Field
PhotosCoordinate

measurement
photo

Measurement spectrum

Spectrum
analysisbrick red lightyellow granite

N42.05685
E94.81883

2214nm吸收谷可能是铝羟基影响，2375nm处吸收谷
是由于镁羟基造成。

light graywhite
plagiogranite

N42.31621
E95.07766

在全波段范围之
内，反射率较高。
该波谱曲线并未
表现出明显的吸收特征。

offwhite biotite
graniteN42.30281
E95.07905

2202nm/2260nm
铝羟基特征吸收
2350nm吸收谷，是 CO32-特征吸收。

Spectrum collection andanalysis in the domestic
demonstration area

The ground spectrum
measurement of different rockores is carried out in thedemonstration area. The types ofrock ores have dark and brightcontrast changes from the overall
tone, and the lithology types
include different types of granite,slate, schist, and alluvial beaches.
⚫ The measured spectra werecollected for the main
vegetation types around Hami.
The main vegetation types were
cotton, corn, and a small
amount of grapes.
⚫

Sample collection from overseas demonstration areas⚫The overseas sample collection area is mainly located in the northof West Urt, Sukhbaatar Province, with east longitude 112°30′～
113°36′ and north latitude 46°51′～47°15′;⚫A total of 52 sets of samples were collected, including granite,rhyolite porphyry, tuff, limestone and other samples.

Sample collection from overseas
demonstration areas

There are over 1,300 hyperspectral data in spectra database,over 500 measured spectra, including 9 different types ofground objects such as water, wheat, soil, some plants,
roads, granite, sloping beaches, and slate.

Progress of China GEO Cooperation InitiativeP l a t f o r m re se arc h an d de ve l o p m e n t
For multi-source heterogeneous remote sensing satellite data, carry out the research and development of thespectrum earth platform data processing system, which can provide standardization, and normalization
processing capabilities, and unify the radiation reference, geometric reference, and spatiotemporal resolution
scale, data product specifications, etc., of multi-source heterogeneous remote sensing satellite data, support
multi-source remote sensing satellite data application collaborative processing capabilities.
Normalize the image data obtained at
different times to a specific time

Normalize the image data with different
resolutions from different satellites todata blocks of standard pixel size.

24Thank you！
Aerospace Information Research Institute(AIR)
Chinese Academy of Sciences(CAS)www.aircas.ac.cn

25