1,957 research outputs found
μκ³΅κ° ν΄μλ ν₯μμ ν΅ν μμ λ³ν λͺ¨λν°λ§
νμλ
Όλ¬Έ(λ°μ¬) -- μμΈλνκ΅λνμ : νκ²½λνμ νλκ³Όμ μ‘°κ²½ν, 2023. 2. λ₯μλ ¬.μ‘μ μνκ³μμ λκΈ°κΆκ³Ό μλ¬ΌκΆμ μνΈ μμ©μ μ΄ν΄νκΈ° μν΄μλ μμ λ³νμ λͺ¨λν°λ§μ΄ νμνλ€. μ΄ λ, μμ±μμμ μ§νλ©΄μ κ΄μΈ‘νμ¬ μμμ§λλ₯Ό μ 곡ν μ μμ§λ§, μ§νλ³νμ μμΈν μ 보λ ꡬλ¦μ΄λ μμ± μ΄λ―Έμ§μ κ³΅κ° ν΄μλμ μν΄ μ νλμλ€. λν μμ±μμμ μκ³΅κ° ν΄μλκ° μμμ§λλ₯Ό ν΅ν κ΄ν©μ± λͺ¨λν°λ§μ λ―ΈμΉλ μν₯μ μμ ν λ°νμ§μ§ μμλ€.
λ³Έ λ
Όλ¬Έμμλ κ³ ν΄μλ μμ μ§λλ₯Ό μΌλ¨μλ‘ μμ±νκΈ° μμ± μμμ μκ³΅κ° ν΄μλλ₯Ό ν₯μμν€λ κ²μ λͺ©νλ‘ νμλ€. κ³ ν΄μλ μμ±μμμ νμ©ν μμ λ³ν λͺ¨λν°λ§μ μ곡κ°μ μΌλ‘ νμ₯νκΈ° μν΄ 1) μ μ§κΆ€λ μμ±μ νμ©ν μμμ΅ν©μ ν΅ν΄ μκ°ν΄μλ ν₯μ, 2) μ λμ μμ±λ€νΈμν¬λ₯Ό νμ©ν 곡κ°ν΄μλ ν₯μ, 3) μ곡κ°ν΄μλκ° λμ μμ±μμμ ν μ§νΌλ³΅μ΄ κ· μ§νμ§ μμ 곡κ°μμ μλ¬Ό κ΄ν©μ± λͺ¨λν°λ§μ μννμλ€. μ΄μ²λΌ, μμ±κΈ°λ° μ격νμ§μμ μλ‘μ΄ κΈ°μ μ΄ λ±μ₯ν¨μ λ°λΌ νμ¬ λ° κ³Όκ±°μ μμ±μμμ μκ³΅κ° ν΄μλ μΈ‘λ©΄μμ ν₯μλμ΄ μμ λ³νμ λͺ¨λν°λ§ ν μ μλ€.
μ 2μ₯μμλ μ μ§κΆ€λμμ±μμμ νμ©νλ μκ³΅κ° μμμ΅ν©μΌλ‘ μλ¬Όμ κ΄ν©μ±μ λͺ¨λν°λ§ νμ λ, μκ°ν΄μλκ° ν₯μλ¨μ 보μλ€. μκ³΅κ° μμμ΅ν© μ, ꡬλ¦νμ§, μλ°©ν₯ λ°μ¬ ν¨μ μ‘°μ , κ³΅κ° λ±λ‘, μκ³΅κ° μ΅ν©, μκ³΅κ° κ²°μΈ‘μΉ λ³΄μ λ±μ κ³Όμ μ κ±°μΉλ€. μ΄ μμμ΅ν© μ°μΆλ¬Όμ κ²½μκ΄λ¦¬ λ±μΌλ‘ μμ μ§μμ μ°κ° λ³λμ΄ ν° λ μ₯μ(λκ²½μ§μ λμ½μλ¦Ό)μμ νκ°νμλ€. κ·Έ κ²°κ³Ό, μκ³΅κ° μμμ΅ν© μ°μΆλ¬Όμ κ²°μΈ‘μΉ μμ΄ νμ₯κ΄μΈ‘μ μμΈ‘νμλ€ (R2 = 0.71, μλ νΈν₯ = 5.64% λκ²½μ§; R2 = 0.79, μλ νΈν₯ = -13.8%, νμ½μλ¦Ό). μκ³΅κ° μμμ΅ν©μ μμ μ§λμ μκ³΅κ° ν΄μλλ₯Ό μ μ§μ μΌλ‘ κ°μ νμ¬, μλ¬Ό μμ₯κΈ°λμ μμ±μμμ΄ νμ₯ κ΄μΈ‘μ κ³Όμ νκ°λ₯Ό μ€μλ€. μμμ΅ν©μ λμ μκ³΅κ° ν΄μλλ‘ κ΄ν©μ± μ§λλ₯Ό μΌκ°κ²©μΌλ‘ μμ±νκΈ°μ μ΄λ₯Ό νμ©νμ¬ μμ± μμμ μ νλ μκ³΅κ° ν΄μλλ‘ λ°νμ§μ§ μμ μλ¬Όλ³νμ κ³Όμ μ λ°κ²¬νκΈΈ κΈ°λνλ€.
μμμ 곡κ°λΆν¬μ μ λ°λμ
κ³Ό ν μ§ νΌλ³΅ λ³ν λͺ¨λν°λ§μ μν΄ νμμ μ΄λ€. κ³ ν΄μλ μμ±μμμΌλ‘ μ§κ΅¬ νλ©΄μ κ΄μΈ‘νλ κ²μ μ©μ΄νκ² ν΄μ‘λ€. νΉν Planet Fusionμ μ΄μνμμ±κ΅° λ°μ΄ν°λ₯Ό μ΅λν νμ©ν΄ λ°μ΄ν° κ²°μΈ‘μ΄ μλ 3m κ³΅κ° ν΄μλμ μ§ν νλ©΄ λ°μ¬λμ΄λ€. κ·Έλ¬λ κ³Όκ±° μμ± μΌμ(Landsatμ κ²½μ° 30~60m)μ κ³΅κ° ν΄μλλ μμμ 곡κ°μ λ³νλ₯Ό μμΈ λΆμνλ κ²μ μ ννλ€. μ 3μ₯μμλ Landsat λ°μ΄ν°μ κ³΅κ° ν΄μλλ₯Ό ν₯μνκΈ° μν΄ Planet Fusion λ° Landsat 8 λ°μ΄ν°λ₯Ό μ¬μ©νμ¬ μ΄μ€ μ λμ μμ± λ€νΈμν¬(the dual RSS-GAN)λ₯Ό νμ΅μμΌ, κ³ ν΄μλ μ κ·ν μμ μ§μ(NDVI)μ μλ¬Ό κ·Όμ μΈμ λ°μ¬(NIRv)λλ₯Ό μμ±νλ νλ€. νμκΈ°λ° νμ₯ μμμ§μ(μ΅λ 8λ
)μ λλ‘ κΈ°λ° μ΄λΆκ΄μ§λλ‘ the dual RSS-GANμ μ±λ₯μ λνλ―Όκ΅ λ΄ λ λμμ§(λκ²½μ§μ νμ½μλ¦Ό)μμ νκ°νλ€. The dual RSS-GANμ Landsat 8 μμμ 곡κ°ν΄μλλ₯Ό ν₯μμμΌ κ³΅κ° ννμ 보μνκ³ μμ μ§μμ κ³μ μ λ³νλ₯Ό ν¬μ°©νλ€(R2> 0.96). κ·Έλ¦¬κ³ the dual RSS-GANμ Landsat 8 μμ μ§μκ° νμ₯μ λΉν΄ κ³Όμ νκ°λλ κ²μ μννλ€. νμ₯ κ΄μΈ‘μ λΉν΄ μ΄μ€ RSS-GANκ³Ό Landsat 8μ μλ νΈν₯ κ° κ°κ° -0.8% μμ -1.5%, -10.3% μμ -4.6% μλ€. μ΄λ¬ν κ°μ μ Planet Fusionμ 곡κ°μ 보λ₯Ό μ΄μ€ RSS-GANλ‘ νμ΅νμκΈ°μ κ°λ₯νλ€. ν€λΉ μ°κ΅¬ κ²°κ³Όλ Landsat μμμ κ³΅κ° ν΄μλλ₯Ό ν₯μμμΌ μ¨κ²¨μ§ κ³΅κ° μ 보λ₯Ό μ 곡νλ μλ‘μ΄ μ κ·Ό λ°©μμ΄λ€.
κ³ ν΄μλμμ μλ¬Ό κ΄ν©μ± μ§λλ ν μ§νΌλ³΅μ΄ 볡μ‘ν 곡κ°μμ νμ μν λͺ¨λν°λ§μ νμμ μ΄λ€. κ·Έλ¬λ Sentinel-2, Landsat λ° MODISμ κ°μ΄ νμ λμ‘° κΆ€λμ μλ μμ±μ κ³΅κ° ν΄μλκ° λκ±°λ μκ° ν΄μλ λμ μμ±μμλ§ μ 곡ν μ μλ€. μ΅κ·Ό λ°μ¬λ μ΄μνμμ±κ΅°μ μ΄λ¬ν ν΄μλ νκ³μ 극볡ν μ μλ€. νΉν Planet Fusionμ μ΄μνμμ± μλ£μ μκ³΅κ° ν΄μλλ‘ μ§νλ©΄μ κ΄μΈ‘ν μ μλ€. 4μ₯μμ, Planet Fusion μ§νλ°μ¬λλ₯Ό μ΄μ©νμ¬ μμμμ λ°μ¬λ κ·Όμ μΈμ 볡μ¬(NIRvP)λ₯Ό 3m ν΄μλ μ§λλ₯Ό μΌκ°κ²©μΌλ‘ μμ±νλ€. κ·Έλ° λ€μ λ―Έκ΅ μΊλ¦¬ν¬λμμ£Ό μν¬λΌλ©ν -μ νΈμν¨ λΈνμ νλμ€ νμ λ€νΈμν¬ λ°μ΄ν°μ λΉκ΅νμ¬ μλ¬Ό κ΄ν©μ±μ μΆμ νκΈ° μν NIRvP μ§λμ μ±λ₯μ νκ°νμλ€. μ 체μ μΌλ‘ NIRvP μ§λλ μ΅μ§μ μ¦μ μμ λ³νμλ λΆκ΅¬νκ³ κ°λ³ λμμ§μ μλ¬Ό κ΄ν©μ±μ μκ°μ λ³νλ₯Ό ν¬μ°©νμλ€. κ·Έλ¬λ λμμ§ μ 체μ λν NIRvP μ§λμ μλ¬Ό κ΄ν©μ± μ¬μ΄μ κ΄κ³λ NIRvP μ§λλ₯Ό νλμ€ νμ κ΄μΈ‘λ²μμ μΌμΉμν¬ λλ§ λμ μκ΄κ΄κ³λ₯Ό 보μλ€. κ΄μΈ‘λ²μλ₯Ό μΌμΉμν¬ κ²½μ°, NIRvP μ§λλ μλ¬Ό κ΄ν©μ±μ μΆμ νλ λ° μμ΄ νμ₯ NIRvPλ³΄λ€ μ°μν μ±λ₯μ 보μλ€. μ΄λ¬ν μ±λ₯ μ°¨μ΄λ νλμ€ νμ κ΄μΈ‘λ²μλ₯Ό μΌμΉμν¬ λ, μ°κ΅¬ λμμ§ κ°μ NIRvP-μλ¬Ό κ΄ν©μ± κ΄κ³μ κΈ°μΈκΈ°κ° μΌκ΄μ±μ 보μκΈ° λλ¬Έμ΄λ€. λ³Έ μ°κ΅¬ κ²°κ³Όλ μμ± κ΄μΈ‘μ νλμ€ νμ κ΄μΈ‘λ²μμ μΌμΉμν€λ κ²μ μ€μμ±μ 보μ¬μ£Όκ³ λμ μκ³΅κ° ν΄μλλ‘ μλ¬Ό κ΄ν©μ±μ μ격μΌλ‘ λͺ¨λν°λ§νλ μ΄μνμμ±κ΅° μλ£μ μ μ¬λ ₯μ 보μ¬μ€λ€.Monitoring changes in terrestrial vegetation is essential to understanding interactions between atmosphere and biosphere, especially terrestrial ecosystem. To this end, satellite remote sensing offer maps for examining land surface in different scales. However, the detailed information was hindered under the clouds or limited by the spatial resolution of satellite imagery. Moreover, the impacts of spatial and temporal resolution in photosynthesis monitoring were not fully revealed.
In this dissertation, I aimed to enhance the spatial and temporal resolution of satellite imagery towards daily gap-free vegetation maps with high spatial resolution. In order to expand vegetation change monitoring in time and space using high-resolution satellite images, I 1) improved temporal resolution of satellite dataset through image fusion using geostationary satellites, 2) improved spatial resolution of satellite dataset using generative adversarial networks, and 3) showed the use of high spatiotemporal resolution maps for monitoring plant photosynthesis especially over heterogeneous landscapes. With the advent of new techniques in satellite remote sensing, current and past datasets can be fully utilized for monitoring vegetation changes in the respect of spatial and temporal resolution.
In Chapter 2, I developed the integrated system that implemented geostationary satellite products in the spatiotemporal image fusion method for monitoring canopy photosynthesis. The integrated system contains the series of process (i.e., cloud masking, nadir bidirectional reflectance function adjustment, spatial registration, spatiotemporal image fusion, spatial gap-filling, temporal-gap-filling). I conducted the evaluation of the integrated system over heterogeneous rice paddy landscape where the drastic land cover changes were caused by cultivation management and deciduous forest where consecutive changes occurred in time. The results showed that the integrated system well predict in situ measurements without data gaps (R2 = 0.71, relative bias = 5.64% at rice paddy site; R2 = 0.79, relative bias = -13.8% at deciduous forest site). The integrated system gradually improved the spatiotemporal resolution of vegetation maps, reducing the underestimation of in situ measurements, especially during peak growing season. Since the integrated system generates daily canopy photosynthesis maps for monitoring dynamics among regions of interest worldwide with high spatial resolution. I anticipate future efforts to reveal the hindered information by the limited spatial and temporal resolution of satellite imagery.
Detailed spatial representations of terrestrial vegetation are essential for precision agricultural applications and the monitoring of land cover changes in heterogeneous landscapes. The advent of satellite-based remote sensing has facilitated daily observations of the Earths surface with high spatial resolution. In particular, a data fusion product such as Planet Fusion has realized the delivery of daily, gap-free surface reflectance data with 3-m pixel resolution through full utilization of relatively recent (i.e., 2018-) CubeSat constellation data. However, the spatial resolution of past satellite sensors (i.e., 30β60 m for Landsat) has restricted the detailed spatial analysis of past changes in vegetation. In Chapter 3, to overcome the spatial resolution constraint of Landsat data for long-term vegetation monitoring, we propose a dual remote-sensing super-resolution generative adversarial network (dual RSS-GAN) combining Planet Fusion and Landsat 8 data to simulate spatially enhanced long-term time-series of the normalized difference vegetation index (NDVI) and near-infrared reflectance from vegetation (NIRv). We evaluated the performance of the dual RSS-GAN against in situ tower-based continuous measurements (up to 8 years) and remotely piloted aerial system-based maps of cropland and deciduous forest in the Republic of Korea. The dual RSS-GAN enhanced spatial representations in Landsat 8 images and captured seasonal variation in vegetation indices (R2 > 0.95, for the dual RSS-GAN maps vs. in situ data from all sites). Overall, the dual RSS-GAN reduced Landsat 8 vegetation index underestimations compared with in situ measurements; relative bias values of NDVI ranged from β3.2% to 1.2% and β12.4% to β3.7% for the dual RSS-GAN and Landsat 8, respectively. This improvement was caused by spatial enhancement through the dual RSS-GAN, which captured fine-scale information from Planet Fusion. This study presents a new approach for the restoration of hidden sub-pixel spatial information in Landsat images.
Mapping canopy photosynthesis in both high spatial and temporal resolution is essential for carbon cycle monitoring in heterogeneous areas. However, well established satellites in sun-synchronous orbits such as Sentinel-2, Landsat and MODIS can only provide either high spatial or high temporal resolution but not both. Recently established CubeSat satellite constellations have created an opportunity to overcome this resolution trade-off. In particular, Planet Fusion allows full utilization of the CubeSat data resolution and coverage while maintaining high radiometric quality. In Chapter 4, I used the Planet Fusion surface reflectance product to calculate daily, 3-m resolution, gap-free maps of the near-infrared radiation reflected from vegetation (NIRvP). I then evaluated the performance of these NIRvP maps for estimating canopy photosynthesis by comparing with data from a flux tower network in Sacramento-San Joaquin Delta, California, USA. Overall, NIRvP maps captured temporal variations in canopy photosynthesis of individual sites, despite changes in water extent in the wetlands and frequent mowing in the crop fields. When combining data from all sites, however, I found that robust agreement between NIRvP maps and canopy photosynthesis could only be achieved when matching NIRvP maps to the flux tower footprints. In this case of matched footprints, NIRvP maps showed considerably better performance than in situ NIRvP in estimating canopy photosynthesis both for daily sum and data around the time of satellite overpass (R2 = 0.78 vs. 0.60, for maps vs. in situ for the satellite overpass time case). This difference in performance was mostly due to the higher degree of consistency in slopes of NIRvP-canopy photosynthesis relationships across the study sites for flux tower footprint-matched maps. Our results show the importance of matching satellite observations to the flux tower footprint and demonstrate the potential of CubeSat constellation imagery to monitor canopy photosynthesis remotely at high spatio-temporal resolution.Chapter 1. Introduction 2
1. Background 2
1.1 Daily gap-free surface reflectance using geostationary satellite products 2
1.2 Monitoring past vegetation changes with high-spatial-resolution 3
1.3 High spatiotemporal resolution vegetation photosynthesis maps 4
2. Purpose of Research 4
Chapter 2. Generating daily gap-filled BRDF adjusted surface reflectance product at 10 m resolution using geostationary satellite product for monitoring daily canopy photosynthesis 6
1. Introduction 6
2. Methods 11
2.1 Study sites 11
2.2 In situ measurements 13
2.3 Satellite products 14
2.4 Integrated system 17
2.5 Canopy photosynthesis 21
2.6 Evaluation 23
3. Results and discussion 24
3.1 Comparison of STIF NDVI and NIRv with in situ NDVI and NIRv 24
3.2 Comparison of STIF NIRvP with in situ NIRvP 28
4. Conclusion 31
Chapter 3. Super-resolution of historic Landsat imagery using a dual Generative Adversarial Network (GAN) model with CubeSat constellation imagery for monitoring vegetation changes 32
1. Introduction 32
2. Methods 38
2.1 Real-ESRGAN model 38
2.2 Study sites 40
2.3 In situ measurements 42
2.4 Vegetation index 44
2.5 Satellite data 45
2.6 Planet Fusion 48
2.7 Dual RSS-GAN via fine-tuned Real-ESRGAN 49
2.8 Evaluation 54
3. Results 57
3.1 Comparison of NDVI and NIRv maps from Planet Fusion, Sentinel 2 NBAR, and Landsat 8 NBAR data with in situ NDVI and NIRv 57
3.2 Comparison of dual RSS-SRGAN model results with Landsat 8 NDVI and NIRv 60
3.3 Comparison of dual RSS-GAN model results with respect to in situ time-series NDVI and NIRv 63
3.4 Comparison of the dual RSS-GAN model with NDVI and NIRv maps derived from RPAS 66
4. Discussion 70
4.1 Monitoring changes in terrestrial vegetation using the dual RSS-GAN model 70
4.2 CubeSat data in the dual RSS-GAN model 72
4.3 Perspectives and limitations 73
5. Conclusion 78
Appendices 79
Supplementary material 82
Chapter 4. Matching high resolution satellite data and flux tower footprints improves their agreement in photosynthesis estimates 85
1. Introduction 85
2. Methods 89
2.1 Study sites 89
2.2 In situ measurements 92
2.3 Planet Fusion NIRvP 94
2.4 Flux footprint model 98
2.5 Evaluation 98
3. Results 105
3.1 Comparison of Planet Fusion NIRv and NIRvP with in situ NIRv and NIRvP 105
3.2 Comparison of instantaneous Planet Fusion NIRv and NIRvP with against tower GPP estimates 108
3.3 Daily GPP estimation from Planet Fusion -derived NIRvP 114
4. Discussion 118
4.1 Flux tower footprint matching and effects of spatial and temporal resolution on GPP estimation 118
4.2 Roles of radiation component in GPP mapping 123
4.3 Limitations and perspectives 126
5. Conclusion 133
Appendix 135
Supplementary Materials 144
Chapter 5. Conclusion 153
Bibliography 155
Abstract in Korea 199
Acknowledgements 202λ°
Remote Sensing in Mangroves
The book highlights recent advancements in the mapping and monitoring of mangrove forests using earth observation satellite data. New and historical satellite data and aerial photographs have been used to map the extent, change and bio-physical parameters, such as phenology and biomass. Research was conducted in different parts of the world. Knowledge and understanding gained from this book can be used for the sustainable management of mangrove forests of the worl
Augmenting Land Cover/Land Use Classification by Incorporating Information from Land Surface Phenology: An Application to Quantify Recent Cropland Expansion in South Dakota
Understanding rapid land change in the U.S. NGP region is not only critical for management and conservation of prairie habitats and ecosystem services, but also for projecting production of crops and biofuels and the impacts of land conversion on water quality and rural transportation infrastructure. Hence, it raises the need for an LCLU dataset with good spatiotemporal coverage as well as consistent accuracy through time to enable change analysis. This dissertation aims (1) to develop a novel classification method, which utilizes time series images from comparable sensors, from the perspective of land surface phenology, and (2) to apply the land cover/land use dataset generated from the phenometrically-based classification approach to quantify crop expansion in South Dakota. A novel classification approach from the perspective of land surface phenology (LSP) uses rich time series datasets. First, surface reflectance products at 30 m spatial resolution from Landsat Collection-1, its newer structureβLandsat Analysis Ready Data, and the Harmonized Landsat Sentinel-2 (HLS) data are used to construct vegetation index time series, including the Enhanced Vegetation Index (EVI), and the 2-band EVI (EVI2), and various spectral variables (spectral band and normalized ratio composites). MODIS Level-3 Land Surface Temperature & Emissivity 8-day composite products at 1 km spatial resolution from both the Aqua and Terra satellites are used to compute accumulated growing degree-days (AGDD) time series. The EVI/EVI2 and AGDD time series are then fitted by two different land surface phenology models: the Convex Quadratic model and the Hybrid Piecewise Logistic Model. Suites of phenometrics are derived from the two LSP models and spectral variables and input to Random Forest Classifiers (RFC) to map land cover of sample areas in South Dakota. The results indicate that classifications using only phenometrics can accurately map major crops in the study area but show limited accuracy for non-vegetated land covers. RFC models using the combined spectralphenological variables can achieve higher accuracies than those using either spectral variables or phenometrics alone, especially for the barren/developed class. Among all sampling designs, the βsame distributionβ modelsβproportional distribution of the sample is like proportional distribution of the populationβtends to yield best land cover prediction. A βsame distributionβ random sample dataset covering approximately 0.25% or more of the study area appears to achieve an accurate land cover map. To characterize crop expansion in South Dakota, a trajectory-based analysis, which considers the entire land cover dataset generated from the LSP-based classifications, is proposed to improve change detection. An estimated cropland expansion of 5,447 km2 (equivalent to 14% of the existing cropland area) occurred between 2007 and 2015, which matches more closely the reports from the National Agriculture Statistics ServiceβNASS (5,921 km2) and the National Resources InventoryβNRI (5,034 km2) than an estimation from a bi-temporal change approach (8,018 km2). Cropland gains were mostly concentrated in 10 counties in northern and central South Dakota. An evaluation of land suitability for crops using the Soil Survey Geographic DatabaseβSSURGO indicates a scarcity in high-quality arable land available for cropland expansion
Estimation of the Conifer-Broadleaf Ratio in Mixed Forests Based on Time-Series Data
Most natural forests are mixed forests, a mixed broadleaf-conifer forest is essentially a heterogeneously mixed pixel in remote sensing images. Satellite missions rely on modeling to acquire regional or global vegetation parameter products. However, these retrieval models often assume homogeneous conditions at the pixel level, resulting in a decrease in the inversion accuracy, which is an issue for heterogeneous forests. Therefore, information on the canopy composition of a mixed forest is the basis for accurately retrieving vegetation parameters using remote sensing. Medium and high spatial resolution multispectral time-series data are important sources for canopy conifer-broadleaf ratio estimation because these data have a high frequency and wide coverage. This paper highlights a successful method for estimating the conifer-broadleaf ratio in a mixed forest with diverse tree species and complex canopy structures. Experiments were conducted in the Purple Mountain, Nanjing, Jiangsu Province of China, where we collected leaf area index (LAI) time-series and forest sample plot inventory data. Based on the Invertible Forest Reflectance Model (INFORM), we simulated the normalized difference vegetation index (NDVI) time-series of different conifer-broadleaf ratios. A time-series similarity analysis was performed to determine the typical separable conifer-broadleaf ratios. Fifteen Gaofen-1 (GF-1) satellite images of 2015 were acquired. The conifer-broadleaf ratio estimation was based on the GF-1 NDVI time-series and semi-supervised k-means cluster method, which yielded a high overall accuracy of 83.75%. This study demonstrates the feasibility of accurately estimating separable conifer-broadleaf ratios using field measurement data and GF-1 time series in mixed broadleaf-conifer forests
Integrated Applications of Geo-Information in Environmental Monitoring
This book focuses on fundamental and applied research on geo-information technology, notably optical and radar remote sensing and algorithm improvements, and their applications in environmental monitoring. This Special Issue presents ten high-quality research papers covering up-to-date research in land cover change and desertification analyses, geo-disaster risk and damage evaluation, mining area restoration assessments, the improvement and development of algorithms, and coastal environmental monitoring and object targeting. The purpose of this Special Issue is to promote exchanges, communications and share the research outcomes of scientists worldwide and to bridge the gap between scientific research and its applications for advancing and improving society
A novel feature fusion approach for VHR remote sensing image classification
6openInternationalInternational coauthor/editorThis article develops a robust feature fusion approach to enhance the classification performance of very high resolution (VHR) remote sensing images. Specifically, a novel two-stage multiple feature fusion (TsF) approach is proposed, which includes an intragroup and an intergroup feature fusion stages. In the first fusion stage, multiple features are grouped by clustering, where redundant information between different types of features is eliminated within each group. Then, features are pairwisely fused in an intergroup fusion model based on the guided filtering method. Finally, the fused feature set is imported into a classifier to generate the classification map. In this work, the original VHR spectral bands and their attribute profiles are taken as examples as input spectral and spatial features, respectively, in order to test the performance of the proposed TsF approach. Experimental results obtained on two QuickBird datasets covering complex urban scenarios demonstrate the effectiveness of the proposed approach in terms of generation of more discriminative fusion features and enhancing classification performance. More importantly, the fused feature dimensionality is limited at a certain level; thus, the computational cost will not be significantly increased even if multiple features are considered.openLiu, S.; Zheng, Y.; Du, Q.; Samat, A.; Tong, X.; Dalponte, M.Liu, S.; Zheng, Y.; Du, Q.; Samat, A.; Tong, X.; Dalponte, M
Analysis of temporal and spatial variations of forest. A case of study in notheastern Armenia
The forest has a crucial ecological role and the continuous forest loss can cause colossal
effects on the environment. As Armenia is one of the low forest covered countries in the
world, this problem is more critical. Continuous forest disturbances mainly caused by illegal
logging started from the early 1990s had a huge damage on the forest ecosystem by
decreasing the forest productivity and making more areas vulnerable to erosion. Another
aspect of the Armenian forest is the lack of continuous monitoring and absence of accurate
estimation of the level of cuts in some years.
In order to have insight about the forest and the disturbances in the long period of time we
used Landsat TM/ETM + images. Google Earth Engine JavaScript API was used, which is an
online tool enabling the access and analysis of a great amount of satellite imagery.
To overcome the data availability problem caused by the gap in the Landsat series in 1988-
1998, extensive cloud cover in the study area and the missing scan lines, we used pixel based
compositing for the temporal window of leaf on vegetation (June-late September).
Subsequently, pixel based linear regression analyses were performed.
Vegetation indices derived from the 10 biannual composites for the years 1984-2014 were
used for trend analysis.
In order to derive the disturbances only in forests, forest cover layer was aggregated and the
original composites were masked. It has been found, that around 23% of forests were
disturbed during the study period
- β¦