Difference between revisions of "Main Page/Research/Smart Maps/dwelling units"
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# add a field to the table for dwelling units per km<sup>2</sup>. | # add a field to the table for dwelling units per km<sup>2</sup>. | ||
#: greater precision than per ft<sup>2</sup> | #: greater precision than per ft<sup>2</sup> | ||
| − | # calculate, e.g. | + | # calculate the field, e.g. |
#: <tt>du_per_km2 = [num_units]*10763910.42/[shape_area]</tt> | #: <tt>du_per_km2 = [num_units]*10763910.42/[shape_area]</tt> | ||
| − | # convert to raster | + | # convert to raster using the field |
#: make a note of cell size, e.g., 10 m cell size = 32.808 ft | #: make a note of cell size, e.g., 10 m cell size = 32.808 ft | ||
# focalsum of the raster | # focalsum of the raster | ||
| Line 17: | Line 17: | ||
# Modify script in ArcToolbox to include arguments/parameters, matching the <tt>sys.argv[]</tt> lines. | # Modify script in ArcToolbox to include arguments/parameters, matching the <tt>sys.argv[]</tt> lines. | ||
| − | Note: this assumes you want the density to be in units/ha | + | Note: this assumes you want the density to be in units/ha. |
| + | |||
| + | |||
<source lang="python"> | <source lang="python"> | ||
| Line 58: | Line 60: | ||
if Cellsize == '#': | if Cellsize == '#': | ||
Cellsize = "32.808" # provide a default value if unspecified | Cellsize = "32.808" # provide a default value if unspecified | ||
| + | StrCellAreaMeters = str((float(Cellsize) / 3.2808)**2) | ||
Neighborhood = sys.argv[4] | Neighborhood = sys.argv[4] | ||
| Line 81: | Line 84: | ||
# Process: DU per hectare... | # Process: DU per hectare... | ||
gp.AddMessage("Du per ha\n") | gp.AddMessage("Du per ha\n") | ||
| − | gp.SingleOutputMapAlgebra_sa(FocalSumR + " / ( (Pi) * sqr ( " + | + | gp.SingleOutputMapAlgebra_sa(FocalSumR + " / ( (Pi) * sqr( " + StrCellAreaMeters + " ))", du_per_ha) |
| − | |||
</source> | </source> | ||
Latest revision as of 23:54, 18 May 2010
Create a smart map raster that represents the count or density of dwelling units
- add a field to the table for dwelling units per km2.
- greater precision than per ft2
- calculate the field, e.g.
- du_per_km2 = [num_units]*10763910.42/[shape_area]
- convert to raster using the field
- make a note of cell size, e.g., 10 m cell size = 32.808 ft
- focalsum of the raster
- note the radius, e.g., 10 cells = 100 m
- gives sum of du/km2 for the circle
- divide by area of the circle to give density
- note unit conversions
The following source code can be used. Requirements:
- Existence of drive W for output. Use subst in Windows for this.
- Modify script in ArcToolbox to include arguments/parameters, matching the sys.argv[] lines.
Note: this assumes you want the density to be in units/ha.
<source lang="python">
- ---------------------------------------------------------------------------
- focal_du_per_ha.py
- Created on: Tue May 18 2010 02:48:36 PM
- (generated by ArcGIS/ModelBuilder)
- Usage: focal_du_per_ha <parcels> <Value_field> <Cellsize> <Neighborhood> <du_per_ha>
- ---------------------------------------------------------------------------
- Import system modules
import sys, string, os, arcgisscripting
- Create the Geoprocessor object
gp = arcgisscripting.create()
- Check out any necessary licenses
gp.CheckOutExtension("spatial")
- Load required toolboxes...
gp.AddToolbox("C:/Program Files (x86)/ArcGIS/ArcToolbox/Toolboxes/Spatial Analyst Tools.tbx") gp.AddToolbox("C:/Program Files (x86)/ArcGIS/ArcToolbox/Toolboxes/Conversion Tools.tbx")
- output dir
outdir = "w:/" if os.path.exists(outdir) == 0: gp.AddMessage("Path does not exist.") exit()
- Script arguments...
parcels = sys.argv[1] if parcels == '#':
parcels = "PIN_ADDRESS" # provide a default value if unspecified
Value_field = sys.argv[2] if Value_field == '#':
Value_field = "du_per_km2" # provide a default value if unspecified
Cellsize = sys.argv[3] if Cellsize == '#':
Cellsize = "32.808" # provide a default value if unspecified
StrCellAreaMeters = str((float(Cellsize) / 3.2808)**2)
Neighborhood = sys.argv[4] if Neighborhood == '#':
Neighborhood = "Circle 10 CELL" # provide a default value if unspecified
du_per_ha = sys.argv[5] if du_per_ha == '#':
du_per_ha = outdir + "du_per_ha.img" # provide a default value if unspecified
- Local variables...
duperkm2 = outdir + "duperkm2.img" FocalSumR = outdir + "FocalSumR.img"
- Process: Polygon to Raster...
gp.AddMessage("Polygon to raster\n") gp.PolygonToRaster_conversion(parcels, Value_field, duperkm2, "CELL_CENTER", "NONE", Cellsize)
- Process: Focal Sum...
gp.AddMessage("FocalSum\n") gp.FocalStatistics_sa(duperkm2, FocalSumR, Neighborhood, "SUM", "DATA")
- Process: DU per hectare...
gp.AddMessage("Du per ha\n") gp.SingleOutputMapAlgebra_sa(FocalSumR + " / ( (Pi) * sqr( " + StrCellAreaMeters + " ))", du_per_ha) </source>
