Using the Majority Tool to add fields to the Block Shape File

The block shape file is definitely bare bones right now! Eventually, the block shape file is loaded into Patchworks with a complete set of stand attributes for each block but the shapefile itself contains only a few minimal fields. Whatever fields exist in your block shapefile will be loaded into the model and stand attributes appended. Additional spatial information can sometimes be very helpful to have available in the model and can be added to the block shapefile using the Majority Tool.

Let's say for example you have decided that you would like to report on volume and havested area by watershed. You already possess a shape file that contains a map of all the watersheds in your management unit. What you would like to know is which blocks are also in the each watershed. A majority function can be performed to tell you if the majority of each block is either in or out of a particular watershed. This tool can be accessed from the Application Launcher to create a CSV lookup file of block number and watershed label that can then be used to calculate a new field in the blocks shape file.

[Note]Note
  1. Select "Compute Zone Majority(raster)" from the Application Launcher in the Data Prep folder.

  2. Base data set: QuickTourIII/blocks/blocks.shp

    Label:BLOCK

Figure 159. Raster Majority Tool dialog


[Note]Note
  1. The Zones that we are trying to identify are the unique watersheds in the Crowsnest planning area.

    Zone data set:QuickTourIII/data/watershed.shp

    Label:WATER_CODE

  2. Provide a cell size for sampling and output file name and location for the lookup table. The cell size determines the resolution of the sampling and therefore the speed of the process as well.

    Cell size:10

    Output file:QuickTourIII/blocks/watershed_lookup.csv

  3. Click 'Finish' to generate the lookup table.

We now have a watershed_lookup.csv file that lists each block and what watershed it is in. Using a database or GIS tool join this lookup file using the BLOCKfield in the block shape file, create a new field in the shapefile and calculate the watershed field over.

[Important]Important

If the block shapes or labels change so will these additional spatial classifications. You must then redo the majority process. They can then be rejoined to the block shape file with the BLOCK id label as the identifier.

[Tip]Tip

Additional fields that have been added to the block shape file as a pre-processing step will be available in the model through the block table. This ultimately means these stratifications will be available in the Access Editor, in the Table Viewer and the Map viewer for querying, mapping and spatially restricting management activities.