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efficient_longest_flow_path_algorithm [2020-01-07 05:12 pm] hchoefficient_longest_flow_path_algorithm [2020-08-07 12:40 pm] (current) – old revision restored (2020-07-05 08:39 pm) hcho
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 ====== Efficient longest flow path algorithm ====== ====== Efficient longest flow path algorithm ======
 +[[Efficient longest flow path algorithm:start|Workspace]]
  
 {{:r_lfp_nc_example_single_warning.png?400|}} {{:r_lfp_nc_example_single_warning.png?400|}}
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 \] \]
  
-A flow path $\FP_i$ is watercourse between a pair of two points $i$ within watershed and the longest flow path $\LFP$ is defined as+A flow path $\FP_i$ is the watercourse between a pair of two points $i$ within the watershed and the longest flow path $\LFP$ is defined as
  
 \[ \[
-  \LFP\in\left\{\FP_i\;\middle\vert\;\left\lVert\FP_i\right\rVert\geq\left\lVert\FP_j\right\rVert\;\forall j\neq i\right\}.+  \LFP\in\left\{\FP_i\;:\;\left|\FP_i\right|\geq\left|\FP_j\right|\;\forall i\neq j\right\}.
 \] \]
  
 The longest flow path plays an important role in hydrologic modeling, but its computation requires multi-step raster calculations for each watershed. This research project aims to improve the current process and efficiency of computing the longest flow path for a lot of watersheds. The longest flow path plays an important role in hydrologic modeling, but its computation requires multi-step raster calculations for each watershed. This research project aims to improve the current process and efficiency of computing the longest flow path for a lot of watersheds.
 +
 +===== Performance comparisons =====
 +
 +{{:fig-ga-ssd-elapsed-vs-subarea-archydropro.png?400|}}
  
 {{:ga-elapsed-time-gwrc.png?400|}} {{:ga-elapsed-time-gwrc.png?400|}}
  
-^ Method        ^  [[https://github.com/HuidaeCho/grass-lfp-deprecated/blob/master/lfp.sh|lfp.sh]]  ^  [[https://github.com/HuidaeCho/grass-lfp-deprecated/blob/master/lfp2.sh|lfp2.sh]]  ^  [[https://github.com/OSGeo/grass-addons/tree/master/grass7/raster/r.lfp|r.lfp]]  ^  Coming soon  ^+^ Method        ^  [[https://github.com/HuidaeCho/grass-lfp-deprecated/blob/master/lfp.sh|lfp.sh]]  ^  [[https://github.com/HuidaeCho/grass-lfp-deprecated/blob/master/lfp2.sh|lfp2.sh]]  ^  [[https://github.com/OSGeo/grass-addons/tree/master/grass7/raster/r.lfp|r.lfp]]  ^  [[https://github.com/OSGeo/grass-addons/tree/master/grass7/raster/r.accumulate|r.accumulate]] ^
 ^ Elapsed time  |  3h 48m                                                                            9h 8m                                                                              |  6h 46m                                                                            **56s**      | ^ Elapsed time  |  3h 48m                                                                            9h 8m                                                                              |  6h 46m                                                                            **56s**      |
 +
 +===== References =====
 +
 +  * Huidae Cho, July 2020 in Press. //__A recursive algorithm for calculating the longest flow path and its iterative implementation.__// [[https://www.journals.elsevier.com/environmental-modelling-and-software/|Environmental Modelling & Software]]. [[https://doi.org/10.1016/j.envsoft.2020.104774|10.1016/j.envsoft.2020.104774]]. SCIE, 2018 Impact Factor 4.552, [[https://idea.isnew.info/publications/A%20recursive%20algorithm%20for%20calculating%20the%20longest%20flow%20path%20and%20its%20iterative%20implementation.pdf|Author's Version]].
 +  * [[https://idea.isnew.info/how-to-calculate-the-longest-flow-path-in-grass-gis.html|How to calculate the longest flow path in GRASS GIS]]
 +
 +{{tag>projects}}
efficient_longest_flow_path_algorithm.1578442342.txt.gz · Last modified: 2020-01-07 05:12 pm by hcho

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