System for Automated Geoscientific Analyses (SAGA) v. 2.1.4

Conrad, Olaf; Bechtel, Benjamin; Bock, Michael; Dietrich, Helge; Fischer, Elke Kerstin; Gerlitz, Lars; Wehberg, Jan; Wichmann, Volker; Böhner, Jürgen

doi:10.5194/gmdd-8-2271-2015

Cited by 191 publications

(115 citation statements)

References 72 publications

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“…The watershed method produces a high degree of over-segmentation during the initial segmentation [12]. A seed-to-saddle difference threshold was then used to merge the over-segments in the SAGA (System for Automated Geoscientific Analyses) [36]. In this study, the values of the seed-to-saddle difference threshold between 0.05 and 0.5 were selected at a 0.05 interval.…”

Section: Methodsmentioning

confidence: 99%

Ash Decline Assessment in Emerald Ash Borer Infested Natural Forests Using High Spatial Resolution Images

Murfitt

Yang

et al. 2016

Remote Sensing

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Abstract:The invasive emerald ash borer (EAB, Agrilus planipennis Fairmaire) infects and eventually kills endemic ash trees and is currently spreading across the Great Lakes region of North America. The need for early detection of EAB infestation is critical to managing the spread of this pest. Using WorldView-2 (WV2) imagery, the goal of this study was to establish a remote sensing-based method for mapping ash trees undergoing various infestation stages. Based on field data collected in Southeastern Ontario, Canada, an ash health score with an interval scale ranging from 0 to 10 was established and further related to multiple spectral indices. The WV2 image was segmented using multi-band watershed and multiresolution algorithms to identify individual tree crowns, with watershed achieving higher segmentation accuracy. Ash trees were classified using the random forest classifier, resulting in a user's accuracy of 67.6% and a producer's accuracy of 71.4% when watershed segmentation was utilized. The best ash health score-spectral index model was then applied to the ash tree crowns to map the ash health for the entire area. The ash health prediction map, with an overall accuracy of 70%, suggests that remote sensing has potential to provide a semi-automated and large-scale monitoring of EAB infestation.

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Section: Methodsmentioning

confidence: 99%

Ash Decline Assessment in Emerald Ash Borer Infested Natural Forests Using High Spatial Resolution Images

Murfitt

Yang

et al. 2016

Remote Sensing

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“…Gridded climate covariate data were aligned by superimposing the vector-based stream network on each of the 10 climate grids (see above), querying grid cells that overlapped with a given stream segment, then calculating the average grid cell value for each segment with SAGA GIS ver. 2.1.2 software ('Add grid values to shapes' function; Conrad et al 2015). All instream and physical habitat covariates were cross-referenced to individual stream segments within the NHDPlus ver.…”

Section: Data Alignment Spatial Filtering and Species' Range Estimamentioning

confidence: 99%

On the use of climate covariates in aquatic species distribution models: are we at risk of throwing out the baby with the bath water?

et al. 2017

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Species distribution models (SDMs) in river ecosystems can incorporate climate information by using air temperature and precipitation as surrogate measures of instream conditions or by using independent models of water temperature and hydrology to link climate to instream habitat. The latter approach is preferable but constrained by the logistical burden of developing water temperature and hydrology models. We therefore assessed whether regional scale, freshwater SDM predictions are fundamentally different when climate data versus instream temperature and hydrology are used as covariates. Maximum entropy (MaxEnt) SDMs were built for 15 freshwater fishes using one of two covariate sets: 1) air temperature and precipitation (climate variables) in combination with physical habitat variables; or 2) water temperature, hydrology (instream variables) and physical habitat. Three procedures were then used to compare results from climate vs instream models. First, equivalence tests assessed average pairwise differences (site‐specific comparisons throughout each species’ range) among climate and instream models. Second, ‘congruence’ tests determined how often the same stream segments were assigned high habitat suitability by climate and instream models. Third, Schoener's D and Warren's I niche overlap statistics quantified range‐wide similarity in predicted habitat suitability from climate vs instream models. Equivalence tests revealed small, pairwise differences in habitat suitability between climate and instream models (mean pairwise differences in MaxEnt raw scores for all species < 3 × 10–4). Congruence tests showed a strong tendency for climate and instream models to predict high habitat suitability at the same stream segments (median congruence = 68%). D and I statistics reflected a high margin of overlap among climate and instream models (median D = 0.78, median I = 0.96). Overall, we found little support for the hypothesis that SDM predictions are fundamentally different when climate versus instream covariates are used to model fish species’ distributions at the scale of the Columbia Basin.

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“…Then, data were averaged from waters shallower than 40 m, each May from 1990 to 2011, using a 0.5°grid. Current vector for velocity and direction were developed using SAGA software (System for Automated Geoscientific Analyses) version 2.2.0 (Conrad et al 2015) and were then converted into grids and motion vectors for Google Earth V7.1.5.1557.…”

Section: Ocean Currentsmentioning

confidence: 99%

Unexpectedly complex gradation of coral population structure in the Nansei Islands, Japan

Zayasu

Nakajima

Sakai

et al. 2016

Ecology and Evolution

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To establish effective locations and sizes of potential protected areas for reef ecosystems, detailed information about source and sink relationships between populations is critical, especially in archipelagic regions. Therefore, we assessed population structure and genetic diversity of Acropora tenuis, one of the dominant stony coral species in the Pacific, using 13 microsatellite markers to investigate 298 colonies from 15 locations across the Nansei Islands in southwestern Japan. Genetic diversity was not significant among sampling locations, even in possibly peripheral locations. In addition, our results showed that there are at least two populations of A. tenuis in the study area. The level of genetic differentiation between these populations was relatively low, but significant between many pairs of sampling locations. Directions of gene flow, which were estimated using a coalescence‐based approach, suggest that gene flow not only occurs from south to north, but also from north to south in various locations. Consequently, the Yaeyama Islands and the Amami Islands are potential northern and southern sources of corals. On the other hand, the Miyako Islands and west central Okinawa Island are potential sink populations. The Kerama Islands and the vicinity of Taketomi Island are potential contact points of genetic subdivision of coral populations in the Nansei Islands. We found that genetic population structure of A. tenuis in the Nansei Islands is more complex than previously thought. These cryptic populations are very important for preserving genetic diversity and should be maintained.

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System for Automated Geoscientific Analyses (SAGA) v. 2.1.4

Cited by 191 publications

References 72 publications

Ash Decline Assessment in Emerald Ash Borer Infested Natural Forests Using High Spatial Resolution Images

Ash Decline Assessment in Emerald Ash Borer Infested Natural Forests Using High Spatial Resolution Images

On the use of climate covariates in aquatic species distribution models: are we at risk of throwing out the baby with the bath water?

Unexpectedly complex gradation of coral population structure in the Nansei Islands, Japan

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