GIS_Exercise 5: Map Algebra

Opened: Monday, 7 October 2019, 9:00 AM
Due: Sunday, 13 October 2019, 6:00 PM

Homework 1:

Continue and finish the task started in class, smoothen the results and export a pdf map of your favorite spot for your cottage. (see slides 05_RASTER_08-10-2019) > slide 24

• The resulting surface is too detailed and continuous; in landscape analysis we want to
present discrete areas.
• Step 1: Round the values and convert them into integer values (your result is
continuous; can’t calculate majority value)
• Int-operator (in Raster Calculator) truncates values to integer (i.e. removes the decimal
part); add 0,5 and then use Int to round
• Step 2: Remove small details with FocalMajority from Spatial Analyst tools ->
Neighborhood -> Focal Statistics
• Use a the input layer as Mask in Environments -> Raster Analysis, because focal
statistics can be calculated outside the study area
• Try different neighborhood sizes (and shapes)
• You might get NoData values where there is more than one majority value
• Step 3: Convert the areas into polygons using Conversion tools -> From
Raster -> Raster to Polygon
• Sometimes manual drawing is required in addition to automatic analysis; you might
have small meaningless polygons that you want to delete
MAR-(include the report as one .pdf-file)

Homework 2:

Go through the Mushroom assignment and ask any question about the process

felix.bourgeau@aalto.fi