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List of reference,algorithms, applications in RS data fusions (contribution are welcome) <img src="https://www.mdpi.com/remotesensing/remotesensing-10-00527/article_deploy/html/images/remotesensing-10-00527-g001.png" alt="drawing" width="600"/>

Table of Contents

Overview of Data Fusion

Trends

There are popular topics and review literatures in different periods.

1992~2000: Data fusion, spatial resolution

2001~2010: classification, unsupervision, change detection, model, multi-resolution, quality, feature extraction Wavelet transform

2011~2021:hyperspectum, deep learning, Heterogeneous, fusion framework, sparse expressions.

Basic Concept

DOD: Data fusion is a multilevel, multifaceted process dealing with the automatic detection, association, correlation, estimation, and combination of data and information from multiple source. Community: Data fusion is a formal framework in which are expressed means and tools for the alliance of data originating from different sources. It aims at obtaining information of greater quality; the exact definition of ‘greater quality’ will depend upon the application

Sensors

SatelliteSensorSpatial ResolutionBandRevisit Cycle
NOAAAVHRR1.1kmVIS,NIR,TIR12h
Terra/AquaMODIS250m,500m,1000m36bands1d
TerraASTER15m,30m,90m14bands(VIS-TIR)16d
LansatMSS79mVNIR18d
TerraMSS+TM30m,120mVNIR,TIR16d
TerraETM+30m,60mVNIR,TIR16d
TerraOLI30m,100mVNIR,TIR16d
OrbView-2Sealifts1kmVIR,NIR,pan1d
SPOTHRV20m3VNIR26d
SPOTVGT1.15km3VNIR+SWIR26d
SPOTHRG/HRS/VGT10m26d
ENVISATMERIS300m15(390-1040nm)35d
Sentinel-2MSI10m,20m,60mVNIR, SWIR5days
Sentinel-1SAR>5mC band12
Sentinel-3SLSTR,OLCI,SRAL,DORIS~300Moptical, micro,1d
HJ-1A/1BUPDATING30m31d
TH-1UPDATING10m58d
BJ-1UPDATING32m
CBERS-01/02UPDATING20m-150m26d
ZY-1 02BUPDATING20m26d
ZY-2 02CUPDATING10m55d
SJ-9AUPDATING10m69d
IRS-P3WIFS/MOS188m5d
updating

Focus, Taxonomy

Research Focus

The application of data fusion in remote sensing is mainly divided in two scenarios:

1. Resolution enhancement:

It aims to provide higher resolution by combining multi modal data. The results are more like to be transition data, base map, or continuous time series for applications need high temporal and spatial resolution.

They are mostly:

For examples:

Sub TopicEnhancementApplications
Super ResolutionSpatialTransition for registration, base map
pan-sharpeningSpatialbase map
spatio-temporal fusionTemporal and Spatialbase map, time series

Typical applications: Plant detection, weather detection, ecology, change detection, land cover, etc.

2. Feature/object detection:

It aims to improve accuracy and precision of specific task, based on complementary property of heterogeneous information in multimodality. Often, temporal continuity can be sacrificed.

They are mostly:

For examples:

Sub TopicEnhancementApplication
Change detectionAccuracy of Change mapLand cover, Building..
Object detectionAccuracy of DetectionCar, Building
SegmentationAccuracy of ClassificationLand Cover, Forest

Typical Applications: change detection, land change coverage, land classification, disaster monitoring, building recognition, vehicle recognition, etc.

3. Data Alignment.

It aims to find and adjust the unlinear connections between different sensors, It could be divided into matching and co-registration, Furthermore, the problems need to be resolved could be regarded as topological and radiation issues. They are mostly:

For examples:

Sub TopicDescription
Radiometric CorrectionAtmospheric effect. etc
Geometric CorrectionCamera, Solar Angle etc
Band AdjustmentFunction based on prior knowledge
BRDF AdjustmentFunction based on vegetation
Registration of Different ModalSAR-Optical, Multi-Temporal..
Adaptive RegistrationDomain, Manifold, Attention Mechanics, Tensor

Taxonomy

Depending on the main problem solved by the model/algorithm, the development of data fusion can be divided into many areas

Current Challengings

In almost every small direction (as shown in the previous subsection). There are a number of issues so authors only list some most important challenges to demonstrate.

As mentioned before, spatial enhancement and fusion of complementary information are main scientific focus. Apart from these, there are:

1. Issues Related to Radiation

IssuesPopular SolutionsDescription
Atmospheric effectRadiometric CorrectionCommonsense
Solar azimuth and elevationRadiometric CorrectionCommonsense
Band pass Adjustmentlinear regressionThe small differences between MSI and OLI equivalent spectral bands need to be adjusted.
Bidirectional Reflectance Distribution effectBRD Function (BRDF)The BRDF is needed in remote sensing for the correction of view and illumination angle effects (for example in image standardization and mosaicking)

2. Issues related to Topology

IssuesPopular SolutionsDescription
Lens Distortion(Camera Calibration in) Geometric CorrectionCommonsense
Error caused by Elevation(SAR and optical)Co-RegistrationPlease see figure1 and figure2
Mis-matching in pixelCo-Registrationin Multi-Temporal, Multi-Sensor, Multi-Angle
Mis-matching in FeatureCo-Registration , Domain Adaptationadaptive alignment as part of model
Mis-matching in ObjectCo-Registration , Attention Mechanicsadaptive alignment as part of model

Figure1. Error due to deviation in DEM, Relationship between error and Angle

enter image description here

3. Issues Related to Data

Noise:

IssuesPopular SolutionsDescription
Noise in SAR(Camera Calibration in) Geometric CorrectionSpeckle
Cloudmask, super resolution, reconstruction, interpolation

Sample:

IssuesPopular SolutionsDescription
Spectral/Index Colinearity, SimilarityPCA, Correlation AnalysisHuges Phenomenon, Statistics
Lack of SamplesData Augmentation, Semi-supervised, GANsOverfitting, low generalization
Unbalanced SamplesLoss functions, updating...weak train in small class
Gap in ResolutionTransition(Super resolution)For 1:2 or higher resolution ratio in multi modal, It will increase the difficulty in data fusion

4. Issues Related to Method and Process

IssuesPopular SolutionsDescription
Computation SpeedAlternative method, cloud service, Parallel computing
Issues related to trainingAI toolslike overfitting, vanished gradient etc.,
Hard to fuse heterogeneityPixel(like unmixing), feature(like feature layers), decision level(like DT)multi-modal
low GeneralizationData augmentation, Domain Adaptive, Pre-traintransferability
lack of InterpretabilityCombination with prior knowledge(Branch, Attention, feature layers, data assimilation )Physics

5. Issues related to Physics

IssuesPopular SolutionsDescription
Intra-class Variation(updating)Small difference between different class
Inter-class variation(updating)Large difference in same class
Landscape HeterogeneityLearning based method,(updating)Variations in high resolution pixel.
Change due to LandcoverLearning based method,(updating)
Abrupt ChangeFunction related to time(updating)disaster etc
Seasonal ChangeFunction related to time(updating)vegetation

Algorithms

There are currently more than 200 spatio-temporal models, so only part of baseline models or popular papers are included.

1.Spatial Resolution Enhancement Algorithms

Multisensor image fusion for spatial resolution enhancement such as pan-sharpening, multi/hyperspectral image fusion, and downscaling of multiresolution imagery

PurposePrincipleMethodPaperCodeFeatures
SpatialComponent (+)Principle Component Analysis(PCA)Shettigara et al.1992Updating
Spatial+Intensy-Hue-Saturation(IHS)Tu et al.2001Updating
Spatial+Brovey Transform(BT)Tu et al.2005Updating
Spatial+Gram-Smidt(GS)Aiazzi et al.2007Updating
Spatial+GS adaptive(GSA)Aiazzi et al.2007Updating
Spatial+GIHS adaptive(GIHSA)Aiazzi et al.2007Updating
SpatialUnmaxingMMT(Zhukov et al.1999)Updating
Spatial+MMT(MERIS,Lansat)(Milla et al.2008)Codeconstraints, Positive of End Member
Spatial+LAC-GAC NDVI(MAselli, 2011)Code
SpatialBaysianBME(Li et al.2013)Code
SpatialHybridUpdating
SpectralLinearWavelet TransformNunez et al.1999Updating
Spectral+High-pass filteringChavez et al.1991Updating
Spectral+Curvelet TransformNencini et al.2007Updating
Spectral+Contour Transformdo and Vetterli 2005Updating
Spectral+Laplacian PyramidSchmitt and Zhu, 2005Updating
Spectral+Smoothing Filter-based intensity modulationLiu,2000Updating
SpectralUnmixingSpectral UnmixingBendoumi et al.2014
Spectral+Nonnegative Matrix UnmixingHuang et al.2008Updating
Spectral+Coupled Nonnegative Matrix UnmaxingYokoya et al.2012Updating
SpectralBayesianMaximum a posterioriHardie et al.2004Updating
SpectralLearningSparse Representation
Spectral+Analysis Sparse Model
Spectral+MRA DNNAzarang et al.2017Code
Spectral+PNNLi et al.2012Updating
Spectral+DRPNNWei et al.2017 MatlabResidual Network
Spectral+MSDCNNZhou et al.2019Python
SpectralHybrid

2. Spatiotemporal Fusion by Traditional Methods

(Normally Prediction by fusing two high temporal and high spatial resolution sensors with correction,Multisensor and multimodal data fusion using a variety of sensors such as optical imaging, SAR, and LiDAR)

SensorPrincipleMethodPaperCodeFeaturesRegistration
Landsat&MODISWeighted FunctionSTARFMGao et al.2006)Python
++STAARCH(Hilker et al.2009)CodeCloud and Snow Cover
++ESTARFM(Zhu et al.2010)IDL,PythonEnhancement in Heterogeneous region
MODIS&landsat+RWSTFM(wang et al.2017)Codekriging Based
1MODIS,2landsat+Prediction Smooth Method(Zhong et al.2018)Codeabrupt change, phenologyManual
MODIS&landsat+SADFATWeng et al.2014CodeConsider Annual temperature Cycle
Unlimited+STITFMWu et al.2014CodeMulti-Sensor LST
+STVIFMLiao et al.2017Codegrowth stages
UnmixingESTDFM(Zhang et al.2013)
+MSTDFAWu et al.2015Codesensor adjustment by linear model
+OB-STVIUM(Lu et al.2016)CodeConsideration of Phenology Change
TemporalBayesianNDVI-BSFM
LearningSPSTFM(Huang et al.2012)Codesparse representation
+One-pair image learning method(Song et al.2012)Codesparse representation
Landsat&AHVRR+EBSCDLWu et al.2015
Landsat&MODIS+ELM(Liu et al.2016 )CodeMatlab
Landsat&MODIS+CSSF(Wei et al.2017)CodeCompression downsampling
Landsat&MODIS+WAIFAMoosavi et al.2015wavelet&ANN
2Landsat&1MODIS+STFDCNNSong et al.2018CodeTransition Image
+DCSFTNCode
HybridFSDAF(Zhu et al.2016)Abrupt Change
+NDVI-LMGM(yu et al.2015)linear growth&unmixing
Two Time seriesOthersSTAIR(Luo et al.2015)Difference, Cloud
Multi Time seriesOthersSTAIR2(Luo et al.2020)

3. Spatio-Temporal Fusion by Neural Network

RegistrationModalProcess LevelMethodPaperCodeFeatures
TraditionalA(T1,T3), B(T2)pixelStfNet(Two Branch)(Liu,2019)CodeFeatures
TraditionalA1-3,B1,3pixelSuper Resolution, weighted function(SONG, 2019)CodeFeatures
TraditionalA1-3,B1,3pixelLevelSuper Resolution, weighted functionLi,2019CodeFeatures
TraditionalA12,B1PIXELDMnet, concatenatelI 2020CodeFeatures
TraditionalA12,B1PIXELCNN, concatenate[Yin 2020](TraditionalA1,B1

4. SAR to Optical

TaskSourceMethodPaperCodeFeatures
Pan-SharpeningLow&HighCNNjin et al.2016CodeResolution enhancedment of MSS
Pan-SharpeningLow&HighCNNG Masi et al.2016CodeEnd-to-End
SAR 2 OpticalSARGANsReyes et al.2018CodeFeature Level, two Stream, semi-auto- Label
SAR 2 Optical(Cloud removal)SARDRNMeraner et al.2018Codecloud removal
SAR 2 OpticalSARsar2optToriya et al.2019Code
Growth PredictionMultiCNNScarpa et al.2018Codepixel level, Sentinel,NDVI fusion and pixel fusion
Growth PredictionSAR&VNIRRandom ForesthECKEL et al.2020Codepixel level, Sentinel

5.Registration

LearningModalProcess LevelMethodPaperCodeFeatures
Registration and SRLow&HighDeep Neural NetworkY. Qu et al.2018Code
RegistrationSAR&OpticalDeep Neural NetworkMou 2017 et al.2018Patch-based
RecognitionHyper&SARDual DCNNLagrange et al.2018CodeFeature Level, two Stream
RecognitionMulti&SARMulti-TaskUNetJIAN et al.2019CodeMulti-Task(Edge, Biniary),xception
RegistrationOptical&SARSiameseMou et al.2018CodeFeature Level, two Stream, semi-auto- Label
RegistrationOptical&SAR3 DNNHughes et al.2020Codehot map, goodness
RegistrationOptical&SARSiamese& Gaussian pyramid coupling quadtreeHe et al.2018CodeCoarse-finer
RegistrationOptical&SARPseudo-Siamese CNNHughes et al.2018Code
SupervisedOptical&SARSiamese CNNMerk et al.2017Code

6. Super Resolution Enhancement

RegistrationModalProcess LevelMethodPaperCodeFeatures
CNNYuan et al.2016CodeEnd-to-End,Transfer Model from CV, hyperspectrum
Low&HighDeep Residual Convolutional Neural NetworkWang et al 2017CodeEnd-to-End,Transfer Model from CV, hyperspectrum
Low&HighSSF-CNNX. Han et al 2018CodeEnd-to-End,Transfer Model from CV, hyperspectrum
Low&HighDeep Neural NetworkR. Dian et al.2017Code
Low&HighSparse Dirichlet-NetY. Qu et al.2018Code
Low&HighDeep Neural NetworkY. Qu et al.2018Code
Low&HighDeep Neural NetworkY. Qu et al.2020CodeChen
MannualHSI-MSIpatch-based,concatenationSuper ResolutionLow&HighDeep Neural NetworkYang et al.2018

7. Classification

RegistrationModalProcess LevelMethodPaperCodeFeatures
ClassificationMultiCNNLagrange et al.2018CodeComparision of existing
ClassificationMultiFusioNetHu et al.2017CodeFeature Level, two Stream
MultiDeepNetsForEOAudebert et al.2017 # Semantic Segmentation of Earth Observation Data Using Multimodal and)CodeFeature Level, two Stream
ClassificationVNIR-DSMDeepUNetAudebert et al.2017CodeChannel Packing
ManualSentinel2,Lansat8, OSM,etc,.Pixel(Concatenation)ResNetQiu et al.2018LCZ maps

8.Change Detction

ModalMethodPaperCodeFeatures
SAR1 (T1, T2)Ratioing/log RatioingPapers
SAR1 (T1, T2)Small wavelet transform(Bovolo,2005)Unsupervised
SAR1 (T1, T2),SAR2 (T1, T2)Markov(Solarna,2018)Unsupervised
More Change detection research please refer to Awesome Change Detection

Quality Assessment

1.Assessment Index With Reference Images.

IndexDescriptionDimensionReference
Spectral angleupdatingspectralUpdating
General image quality indexupdatingspectralUpdating
Root Mean Square Errorupdatingspectral&temporalUpdating
Relative mean spectral errorupdatingspectral&temporal
Signal-to-noise ratioupdatingspatialUpdating
Peak signal-to-noise ratioupdatingspatialUpdating
Correlation coefficientupdatingspatial&temporalUpdating
Structural similarity coefficientspatial&temporalUpdating
Global integrated error indexupdatingspatial&spectralUpdating
Average errorupdatingspatialUpdating

2.Assessment Index Without Reference Images.

IndexDescriptionDimensionReference
Average valueupdatingspatial,spectral
Varianceupdatingspatial,temporalUpdating
Standard deviationupdatingspatial,temporalUpdating
Information entropyupdatingspatial,temporalUpdating
Mean gradientupdatingspatial,temporalUpdating

Community

IEEE GRSS data fusion contest(Link)

Year: 2020 Title: Global Land Cover Mapping with Weak Supervision Data: MSS, SENTINEL MSS

Track1:

Main AuthorApproachCode
RobinsonA combination of iterative clustering and epitome representationsCode
Yu XiaMulti-branch fusion of unsupervised multi-resolution segmentation, random forest classification of remote sensing indexes, and convolutional neural network predictions with post-processing based on expert priorsWHU_YuXia
Daniele CerraAutomated label pre-processing, a Gaussian Naive Bayes classifier trained on cluster centroids, and classes obtained by k-means clustering and random forests with bag of words features, followed by classification refinement designed for specific classesPineapples
Track 2:
Main AuthorApproachCode
------
Huijun ChenAn ensemble of random forests trained on refined labelsAntonia
Daniele CerraAs Track 1 third, but random forests trained on high-resolution labels for validation dataPineapples
Shuting YinA combination of random forests, k-means, and DeepLabv3++ with postprocessing and retrainingdfchen

Year: 2019 Title: Reconstruct both a 3D geometric model and a segmentation of semantic classes for an urban scene Data: WorldView-3, VIR, NIR, LiDAR

Track 1: Single-view semantic 3D

Main AuthorApproachCode
Saket KunwarAn ensemble of random forests trained on refined labelsnest
Zhuo ZhengA pyramid on pyramid network based on an encoder-dual decoder frameworkRSIDEA-WHU
Track 2: Pairwise semantic stereo
Main AuthorApproachCode
------
Hongyu ChenA modified version of Pyramid Stereo Matching Network (PSMNet) and Disparity Fusion Segmentation Net (DFSN)BurningAllthing
Rongjun QinU-Net and Pyramid Stereo Matching Network (PSMNet)qin.324

Track 3: Multi-view semantic stereo

Main AuthorApproachCode
Pablo d’AngeloSemi-global matching and an ensemble of CNN classifiers with ad hoc detectorsPanoptes
Rongjun QinSemi-global matching and U-Netqin.324
Track 4: 3D point cloud classification
Main AuthorApproachCode
------
Lian YanchaoAn ensemble of random forests trained on refined labelsnest
Jia MeixiaAttention-SIFT Net (AS net) based on Pointnet++ and PointSIFTaijinli0613

Year: 2018 Title: urban land use and land cover classification Data: Hyper, Multi, Lidar, RGB(5cm) updating

Main AuthorApproachCode
Yonghao XuFully convolutional networks and post-classification with topological relationships among different objectsGaussian
Daniele CerraDeep convolutional and shallow neural networks on a simplified set of classes, completed by a series of specific detectors and ad hoc classifiersdlrpba
Sergey SukhanovEnsemble learning based on several classifiers, including convolutional neural networks, gradient boosting machines, and random forests, followed by post-processing techniquesAGTDA

2017,2016,2015 are updating!

Discussion

Software and Open Source Tools

We will focus on cloud computing and some important machine learning libraries

Cloud Services

Useful Library

Database

TERMS

There are terms which are slightly different from those in other areas.

Measurements(SIGNAL/image): Primarily the outputs of a sensor,represent the raw information, normally in format of singal, images. The elementary support of the measurement is a pixel in the case of an image, and is called a sample in the general case

Object: It is defined by its properties, e.g., its color, its materials, its shapes, its neighborhood, etc. It can be a field, a building, the edge of a road, a cloud, an oceanic eddy, etc.

attribute(Feature): It is a property of an object. Mathematical attribute: aggregation of measurements made for each of the elements of the object Modality: It refers to the raw input used by the sensors.

Spatial context of a pixel, computed by local variance, or structure function or any spatial operator. This operation can be extended to time context in the case of time-series of measurements. Equivalent terms are local variability, local fluctuations, spatial or time texture, or pattern.