Updated Class 12

Author: marecotec

Classes/12_Rasters/ALL FILES.zip

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+
+#####
+# Step 3 - Rasters and numpy
+#####
+
+# Numpy is a exceptionally powerful package for Python that gives incredible scientific computing functionality.
+# Some basic functionality has been built into arcpy that allows us to interact with it in a fairly seamless manner.
+
+# Review the code below, this is a simple conversion that we are doing, converting Meters to Feet in an elevation
+# raster. Of course you could do this using Raster Calculator, but what if you want to do more complex statistics,
+# model simulations and so on?
+
+# Be aware that the size of the raster is crucial as the resulting numpy array will reside in your computer
+# memory, so no 10gb files!
+
+import arcpy
+
+arcpy.env.overwriteOutput = True
+arcpy.env.workspace = r"Z:\Andy's Documents\Teaching and students\URI\NRS - GIS Python Course\Github\Course_ArcGIS_Python\Classes\12_Rasters\Step_3_Data"
+inRas = arcpy.Raster("etopo10")
+lowerLeft = arcpy.Point(inRas.extent.XMin,inRas.extent.YMin)
+cellSize = inRas.meanCellWidth
+
+arr = arcpy.RasterToNumPyArray(inRas,nodata_to_value=0)
+
+# Print the resulting array
+print arr.shape
+
+# Now lets convert m to feet
+arrFeet = arr * 3.28084
+
+newRaster = arcpy.NumPyArrayToRaster(arrFeet, lowerLeft, cellSize, value_to_nodata=0)
+newRaster.save("etopo10_ft.tif")
+
+
+# Task: Using the etopo10 dataset and a NumPyArray, extract only land values, replacing them with null data. Hint:
+# arr[arr < 0] = -9999

Classes/12_Rasters/ALL_FILES.zip

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+
+#####
+# Step 3 - Rasters and numpy
+#####
+
+# Numpy is a exceptionally powerful package for Python that gives incredible scientific computing functionality.
+# Some basic functionality has been built into arcpy that allows us to interact with it in a fairly seamless manner.
+
+# Review the code below, this is a simple conversion that we are doing, converting Meters to Feet in an elevation
+# raster. Of course you could do this using Raster Calculator, but what if you want to do more complex statistics,
+# model simulations and so on?
+
+# Be aware that the size of the raster is crucial as the resulting numpy array will reside in your computer
+# memory, so no 10gb files!
+
+import arcpy
+
+arcpy.env.overwriteOutput = True
+arcpy.env.workspace = r"Z:\Andy's Documents\Teaching and students\URI\NRS - GIS Python Course\Github\Course_ArcGIS_Python\Classes\12_Rasters\Step_3_Data"
+inRas = arcpy.Raster("etopo10")
+lowerLeft = arcpy.Point(inRas.extent.XMin,inRas.extent.YMin)
+cellSize = inRas.meanCellWidth
+
+arr = arcpy.RasterToNumPyArray(inRas,nodata_to_value=0)
+
+# Print the resulting array
+print arr.shape
+
+# Now lets convert m to feet
+arrFeet = arr * 3.28084
+
+newRaster = arcpy.NumPyArrayToRaster(arrFeet, lowerLeft, cellSize, value_to_nodata=0)
+newRaster.save("etopo10_ft.tif")
+
+
+# Task: Using the etopo10 dataset and a NumPyArray, extract only land values, replacing them with null data. Hint:
+# arr[arr < 0] = -9999
+
+import arcpy
+
+arcpy.env.workspace = r"Z:\Andy's Documents\Teaching and students\URI\NRS - GIS Python Course\Github\Course_ArcGIS_Python\Classes\12_Rasters\Step_3_Data"
+inRas = arcpy.Raster("etopo10")
+lowerLeft = arcpy.Point(inRas.extent.XMin,inRas.extent.YMin)
+cellSize = inRas.meanCellWidth
+
+arr = arcpy.RasterToNumPyArray(inRas,nodata_to_value=0)
+
+# Print the resulting array
+print arr.shape
+
+# Now lets convert m to feet
+arr[arr < 0] = -9999
+
+newRaster = arcpy.NumPyArrayToRaster(arr, lowerLeft, cellSize, value_to_nodata=-9999)
+newRaster.save("etopo10_land.tif")