All,Below is a python script I developed for extracting out elevation information for a point dataset. Basically it gets a list of ID's from a table (the barrier ID table) then for each ID is selects 2 points from a point Featureclass, it then snaps them to the flow accumulation grid, extracts the values and writes the min and max value to an output table.The code runs fine but eventually crashes after 3 or 4 hours. I then have to compact the personal geodatabase and restart the code from the point it crashed. What I've noticed is that the personal geodatabase just keeps on getting bigger until it hits the 2GB limit (hence the code failing). So my question to all you python gurus is how do I change my code to stop this annoying behaviour? I tried putting a "compact" in every 500th ID but it comes up with an error.'''
Description: Extracts the minimum and maximum DEM values for each barriers
upstream and downstream limit
Constraints: Designed to work only in the 9.3 ArcGIS system.
Author: Duncan Hornby
Email: ddh@geodata.soton.ac.uk
Created: 6/8/2010
'''
# Import system modules
import sys, arcgisscripting
# Create the Geoprocessor object & set any environment settings
gp = arcgisscripting.create(9.3)
gp.SetProduct("ArcView")
gp.CheckOutExtension("Spatial")
gp.Workspace = "c:\\temp\\"
gp.cellSize = "50"
gp.OverWriteOutput = 1
# Set any objects and variables
tempRaster = "snapIntPnt"
tempRaster2 = "ExtDEM"
tempLayer = "tempPointLayer.shp"
pgd = "G:\LiveData\UC1168_Sediment_WQ0128\Vector\pGDB93_UC1168_Output.mdb"
# Get parameters
BarrierIDTable = gp.GetParameterAsText(0)
IntersectionPointLayer = gp.GetParameterAsText(1)
FlowAccum = gp.GetParameterAsText(2)
DEM = gp.GetParameterAsText(3)
Output = gp.GetParameterAsText(4)
gp.SnapRaster = FlowAccum
# Create a cursor over the barrier ID table
rows = gp.SearchCursor(BarrierIDTable,"","","OBSTRUCTID","")
row = rows.next()
# Iterate through the rows in the cursor
while row:
# Get barrier ID
bID = row.GetValue("OBSTRUCTID")
## # Check to see if we should compact the geodatabase at every 500th
## if bID%500 == 0:
## gp.AddWarning("Compacting GeoDatabase...")
## gp.Compact_management(pgd)
gp.AddMessage("Processing Barrier: " + str(bID))
# Select all the intersection points that belong to this barrier
gp.SetProgressorLabel("Selecting intersection points...")
gp.SelectLayerByAttribute_management(IntersectionPointLayer,"NEW_SELECTION","[OBSTRUCTID] = " + str(bID) + " AND [UseAsSlopeLimit] = 'Y'")
# Convert selection to a layer so we can get an extent
gp.SetProgressorLabel("Getting extent of selection...")
gp.CopyFeatures_management(IntersectionPointLayer,tempLayer)
obj = gp.Describe(tempLayer)
gp.Extent = obj.Extent
del obj # Destroy object
# Snap selected points to flow accumulation grid
gp.SetProgressorLabel("Snapping selected points to flow accumulation grid...")
gp.SnapPourPoint_sa(IntersectionPointLayer,FlowAccum,tempRaster,"25","OBSTRUCTID")
# Now extract the DEM values from the pre-prepared raster layer
gp.SetProgressorLabel("Extracting DEM cells...")
gp.ExtractByMask_sa(DEM,tempRaster,tempRaster2)
# Extract the properties from this raster
gp.SetProgressorLabel("Reading raster properties...")
resultObj = gp.GetRasterProperties_management(tempRaster2,"MINIMUM")
zMin = resultObj.GetOutput(0)
resultObj = gp.GetRasterProperties_management(tempRaster2,"MAXIMUM")
zMax = resultObj.GetOutput(0)
gp.AddMessage("Elevation - Min:" + str(zMin) + " , Max: " + str(zMax))
del resultObj # Destroy object
# Write data to output table
gp.SetProgressorLabel("Updating output table...")
InsertRows = gp.InsertCursor(Output) # Create insert cursor for table
aNewRow = InsertRows.NewRow()
aNewRow.SetValue("OBSTRUCTID",bID)
aNewRow.SetValue("MinEle",zMin)
aNewRow.SetValue("MaxEle",zMax)
InsertRows.InsertRow(aNewRow)
InsertRows.Reset()
del aNewRow # Destroy object
del InsertRows # Destroy object
# Get next Barrier ID
row = rows.next()
# Return extension license
gp.CheckInExtension("Spatial")
