Tool Name	Zonal Grid Statistics
Tool ID	5
Library ID	statistics_grid
Version	2.0
Author(s)	Volker Wichmann (c) 2005-2022

Description

The tool allows one to calculate zonal statistics over a set of input grids and reports the statistics in a table.
The tool first creates a contingency table of unique condition units (UCUs) on which the statistics are calculated. These UCUs are delineated from a zonal grid (e.g. sub catchments) and optional categorical grids (e.g. landcover, soil, ...). The derived UCUs can be output as a grid dataset.
The tool then calculates descriptive statistics (n, min, max, mean, standard deviation and sum) for each UCU from (optional) grids with continuous data (e.g. slope). A grid storing aspect must be treated specially (circular statistics), please use the "Aspect" input parameter for such a grid.

The tool has four different modes of operation:
(1) only a zonal grid is used as input. This results in a simple contingency table with the number of grid cells in each zone.
(2) a zonal grid and additional categorical grids are used as input. This results in a contingency table with the number of cells in each UCU.
(3) a zonal grid and additional grids with continuous data are used as input. This results in a contingency table with the number of cells in each zone and the corresponding statistics for each continuous grid.
(4) a zonal grid, additional categorical grids and additional grids with continuous data are used as input. This results in a contingency table with the number of cells in each UCU and the corresponding statistics for each continuous grid.

Depending on the mode of operation, the output table contains information about the categorical combination of each UCU, the number of cells in each UCU and the statistics for each UCU. A typical output table may look like this:

ID UCU	ID Zone	ID 1stCat	ID 2ndCat	Count UCU	N 1stCont	MIN 1stCont	MAX 1stCont	MEAN 1stCont	STDDEV 1stCont	SUM 1stCont
1	0	2	6	6	6	708.5	862.0	734.5	62.5	4406.8
2	0	3	4	106	106	829.1	910.1	848.8	28.5	89969.0

Note: in the case you like to convert some one of the statistics back to a grid dataset, you can use the following procedure. Run the tool and output the UCU grid. Then edit the output table to match your needs (delete all fields besides the UCU identifier and the fields you like to create grids from). Then use both datasets in the "Grids from Classified Grid and Table" tool.

Parameters

Name	Type	Identifier	Description	Constraints
Input
Zone Grid	grid, input	ZONES	The grid defining the zones to analyze [NoData;categorical values].
Categorical Grids	grid list, input, optional	CATLIST	Additional grids used to delineate the UCUs [NoData;categorical values].
Grids to Analyse	grid list, input, optional	STATLIST	The grids with continuous data for which the statistics are calculated [NoData;continuous values].
Aspect	grid, input, optional	ASPECT	A grid encoding the aspect of each cell [radians].
Output
UCUs	grid, output, optional	UCU	The derived unique condition areas (UCU).
Zonal Statistics	table, output	OUTTAB	The summary table with the statistics for each UCU.
Options
Short Field Names	boolean	SHORTNAMES	Shorten the field names to ten characters (as this is the limit for field names in shapefiles).	Default: 1