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Grid Functions

Grid Functions. FE 423 - Lecture 3b. SCHEDULE. OUTLINE. Grid Function List Writing Equations Conditional Setnull/Isnull Local/Focal/Zonal Functions Project/Disc Management. Grid Function List. ArcView Help: Grid (Class) We only use those ending in :Grid and not those with Ftab

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Grid Functions

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  1. Grid Functions FE 423 - Lecture 3b

  2. SCHEDULE

  3. OUTLINE • Grid Function List • Writing Equations • Conditional • Setnull/Isnull • Local/Focal/Zonal Functions • Project/Disc Management

  4. Grid Function List ArcView Help: Grid (Class) • We only use those ending in :Grid • and not those with • Ftab • aPrj • aGridList

  5. WRITING EQUATIONS In math: y=x2 Old computer code y=sqr(x) Object oriented code [x].sqr Nesting log(sin(x))  [x].sin.log parameters [dem].hillshade(315,45,1)

  6. Conditional Statement0/1 to grid0/grid1 • If condition • then action1 • else action0 • in Avenue aGrid.Con (yesGrid, noGrid) • Example ([snow]>[melt]).Con(([snow]-[melt]),0.Asgrid)

  7. Null Data • Cells with no value (not 0) are null Some functions require null cells Some functions make null cells • Setnull: sets specific cells to null ([stand age]>100.Asgrid).SetNull([stand age]) • Isnull: is a cell value null? ([landslides].Isnull).Con(0.Asgrid,1.Asgrid)

  8. Local/Focal/Zonal Functions • Local Functions at each cell [grid1]+[grid2] • Focal Functions around each cell [dem].FocalStats(#GRID_STATYPE_MEAN, NbrHood.Make, False) • Zonal Functions within the zone of each cell ([dem]>1000.asgrid).ZonalFill([dem])

  9. PROJECT MANAGEMENTevery project tells a story • Make project name explanatory • Make themes name explanatory • Make legend categories clear • Comment themes to explain thinking • Remove useless themes • Separate unrelated themes by project

  10. DISC MANAGEMENTmake and move everything together • Use one directory on all machines C:/temp/email_name/this_project/ • Set Working Directory • Save coverages, files, project, report • zip directory to move • by network • by zip drive • email/ftp

  11. Reading from ArcDoc • Spatial modeling • Cell-based Modeling with GRID • Surface hydrologic analysis

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