The effect of atmospheric and topographic corrections on the vegetation density mapping using several vegetation indices: a case study in Arjuno-Welirang volcanoes, East Java

Abstract. Vegetation indices (VIs) have been extensively employed as a feature for dry matter (DM) estimation. During the past five decades more than a hundred vegetation indices have been proposed. Inevitably, the selection of the optimal index or subset of indices is not trivial nor obvious. This study, performed on a year-round observation of perennial ryegrass (n&thinsp;=&thinsp;900), indicates that for this response variable (i.e. kg.DM.ha&minus;1), more than 80% of indices present a high degree of collinearity (correlation&thinsp;&gt;&thinsp;|0.8|.) Additionally, the absence of an established workflow for feature selection and modelling is a handicap when trying to establish meaningful relations between spectral data and biophysical/biochemical features. Within this case study, an unsupervised and supervised filtering process is proposed to an initial dataset of 97 VIs. This research analyses the effects of the proposed filtering and feature selection process to the overall stability of final models. Consequently, this analysis provides a straightforward framework to filter and select VIs. This approach was able to provide a reduced feature set for a robust model and to quantify trade-offs between optimal models (i.e. lowest root mean square error &ndash; RMSE&thinsp;=&thinsp;412.27&thinsp;kg.DM.ha&minus;1) and tolerable models (with a smaller number of features &ndash; 4 VIs and within 10% of the lowest RMSE.)

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The effect of atmospheric correction methods on the relationship between vegetation indices and canopy cover (Case study: Marjan rangelands of Borujen)

Journal of Geospatial Information Technology ◽

10.29252/jgit.7.2.133 ◽

2019 ◽

Vol 7 (2) ◽

pp. 133-153

Author(s):

Fatemeh Pordel ◽

Ataollah Ebrahimi ◽

Zahra Azizi ◽

◽

...

Keyword(s):

Vegetation Indices ◽

Atmospheric Correction ◽

Canopy Cover ◽

The Relationship

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Estimation of Above-Ground Mangrove Biomass Using Landsat-8 Data- Derived Vegetation Indices: A Case Study in Quang Ninh Province, Vietnam

Forest and Society ◽

10.24259/fs.v5i2.13755 ◽

2021 ◽

pp. 506-525

Author(s):

Hai-Hoa Nguyen ◽

Huy Duc Vu ◽

Achim Röder

Keyword(s):

Vegetation Indices ◽

Landsat 8 ◽

Mangrove Forests ◽

Estimation Model ◽

The Status ◽

Good Potential ◽

The Mean ◽

Accuracy Assessments ◽

Quang Ninh

This study aimed to map the status of mangrove forests over the coasts of Hai Ha District and Mong Cai City in Quang Ninh Province by using 2019 Landsat-8 imagery. It then developed the AGB estimation model of mangrove forests based on the AGB estimation-derived plots inventory and vegetation indices-derived from Landsat-8 data. As results, there were five land covers identified, including mangrove forests, other vegetation, wetlands, built-up, and water, with the overall accuracy assessments of 80.0% and Kappa coefficient of 0.74. The total extent of mangrove forests was estimated at 4291.2 ha. The best AGB estimation model that was selected to estimate the AGB and AGC of mangrove forests for the whole coasts of Hai Ha District and Mong Cai City is AGB= 30.38 + 911.95*SAVI (R2=0.924, PValue <0.001). The model validation assessment has confirmed that the selected AGB model can be applied to Hai Ha and Mong Cai coasts with the mean difference between AGB observed and AGB predicted at 16.0 %. This satisfactory AGB model also suggests a good potential for AGB and AGC mapping, which offer the carbon trading market in the study site. As the AGB model selected, the total AGB and AGC of mangrove forests were estimated at about 14,600,000 tons and 6,868,076 tons with a range of from 94.0 - 432.0 tons ha-1, from 44.2 - 203.02 tons ha-1, respectively. It also suggests that the newly-developed AGB model of mangrove forests can be used to estimate AGC stocks and carbon sequestration of mangrove forests for C-PFES in over the coasts of Hai Ha District and Mong Cai City, which is a very importantly financial source for mangrove forest managers, in particular for local mangrove protectors.

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Riparian Vegetation Density Mapping of an Extremely Densely Vegetated Confined Floodplain

Hydrology ◽

10.3390/hydrology8040176 ◽

2021 ◽

Vol 8 (4) ◽

pp. 176

Author(s):

István Fehérváry ◽

Tímea Kiss

Keyword(s):

Riparian Vegetation ◽

Woody Species ◽

Submerged Vegetation ◽

Vegetation Types ◽

Vegetation Density ◽

Vegetation Zone ◽

Density Mapping ◽

Vegetation Zones ◽

Branch Density ◽

Vegetation Patches

The most crucial function of lowland-confined floodplains with low slopes is to support flood conveyance and fasten floods; however, obstacles can hinder it. The management of riparian vegetation is often neglected, though woody species increase the vegetation roughness of floodplains and increase flood levels. The aims are (1) to determine the branch density of various riparian vegetation types in the flood conveyance zone up to the level of artificial levees (up to 5 m), and (2) to assess the spatial distribution of densely vegetated patches. Applying a decision tree and machine learning, six vegetation types were identified with an accuracy of 83%. The vegetation density was determined within each type by applying the normalized relative point density (NRD) method. Besides, vegetation density was calculated in each submerged vegetation zone (1–2 m, 2–3 m, etc.). Thus, the obstacles for floods with various frequencies were mapped. In the study area, young poplar plantations offer the most favorable flood conveyance conditions, whereas invasive Amorpha thickets and the dense stands of native willow forests provide the worst conditions for flood conveyance. Dense and very dense vegetation patches are common in all submerged vegetation zones; thus, vegetation could heavily influence floods.

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An improved hazard assessment chart for rock falls in near vertical blocky rock environments

10.21203/rs.3.rs-161209/v1 ◽

2021 ◽

Author(s):

Fhatuwani Sengani ◽

Mulenga Francois

Keyword(s):

Slope Angle ◽

Vegetation Density ◽

Rock Falls ◽

Structural Mapping ◽

Initial Height ◽

Rockfall Hazard ◽

Final Destination ◽

Bedding Planes ◽

Hazard Rating

Abstract The purpose of the study was to perform rockfall stability analysis and develop an improved rockfall hazard matrix chart using the R518 road in Limpopo as the case study. The study entailed structural mapping, wedge simulation using stereonet plots. The RocFall software was then used to identify the parameters that influence the occurrence of rockfall. The software was also used to monitor the variations in the kinetic energy of rolling, bouncing or falling rocks. The effects of the initial height and velocity of falling rocks on the final destination of fragments were also explored. Results showed that the selected area along the R518 road consists of joints and bedding planes. These features weaken the rock mass and create wedges that can potentially fall. Simulations with RocFall, on the other hand, indicated that slope height, vegetation density, slope angle, the velocity of the falling rock largely contribute to the extent that the broken rock could reach. From the empirical and numerical findings, an improved rockfall hazard rating chart was proposed. The chart was found to be suitable for the rating of level of rockfall hazard along highways and roads.

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The Use of the Land Survey Record to Assess Changes in Vegetation Structure. A Case Study From the Darling Downs, Queensland, Australia.

The Rangeland Journal ◽

10.1071/rj9980132 ◽

1998 ◽

Vol 20 (1) ◽

pp. 132 ◽

Cited By ~ 8

Author(s):

RJ Fensham ◽

JE Holman

Keyword(s):

Vegetation Structure ◽

Canopy Cover ◽

Vegetation Density ◽

Crown Cover ◽

Standard Application ◽

Land Survey ◽

Minor Vegetation ◽

Structural Category ◽

Historical Photographs

Fifteen references to vegetation structure from the historical land survey record for the eastern Darling Downs were calibrated with historical photographs to determine the use of the surveyors' structural terminology (Open: 'open', 'light': Dense: 'heavy', 'thick', 'dense'). Sites with less than 40% canopy cover were only described by terms included within the Open category, and sites with greater than 50% canopy cover were only described by terms included within the Dense category. These results provide calibrations of the surveyors' structural terminology indicating terms were unambiguously applied outside the 40-50% canopy cover range. The use of corner tree distances as an absolute measure of vegetation density is warned against because corner trees had to meet certain criteria and were not necessarily the nearest tree to any corner. However, the distance from allotment corners to "corner trees" provided a measure of the relative use of the surveyor's structural epithets and is consistent with standard application among their fraternity. Survey records dating from 1864-1910 were compared with the structure of existing remnants (projective crown cover measured from recent 1:25,000 aerial photography) to assess changes in vegetation structure. The analysis suggests that 88% of the 34 sites included in the analysis have not changed from the broad structural category that was assigned by the surveyors. Using the assumptions developed by this study, two sites were assessed as having thickened substantially. These results suggest that only minor vegetation thickening has occurred in the Darling Downs since the early land surveys. This conclusion is supported by direct comparison of the historical photographs with existing remnants. indicating that only one site out of 17 has thickened substantially.

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