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