Grid Functions FE 423 Lecture 3 b SCHEDULE
Grid Functions FE 423 - Lecture 3 b
SCHEDULE
OUTLINE • • • Grid Function List Writing Equations Conditional Setnull/Isnull Local/Focal/Zonal Functions Project/Disc Management
Grid Function List Arc. View Help: Grid (Class) • We only use those ending in : Grid • and not those with – Ftab – a. Prj – a. Grid. List
WRITING EQUATIONS In math: y=x 2 Old computer code y=sqr(x) Object oriented code [x]. sqr Nesting parameters log(sin(x)) [x]. sin. log [dem]. hillshade(315, 45, 1)
Conditional Statement 0/1 to grid 0/grid 1 • If condition – then action 1 – else action 0 • in Avenue a. Grid. Con (yes. Grid, no. Grid) • Example ([snow]>[melt]). Con(([snow]-[melt]), 0. Asgrid)
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). Set. Null([stand age]) • Isnull: is a cell value null? ([landslides]. Isnull). Con(0. Asgrid, 1. Asgrid)
Local/Focal/Zonal Functions • Local Functions at each cell [grid 1]+[grid 2] • Focal Functions around each cell [dem]. Focal. Stats(#GRID_STATYPE_MEAN, Nbr. Hood. Make, False) • Zonal Functions within the zone of each cell ([dem]>1000. asgrid). Zonal. Fill([dem])
PROJECT MANAGEMENT every 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
DISC MANAGEMENT make 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
Reading from Arc. Doc • Spatial modeling – Cell-based Modeling with GRID • Surface hydrologic analysis
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