R: Spatial temporal analysis of moving polygons

stamp {stampr}

R Documentation

Spatial temporal analysis of moving polygons

Description

This function generates a sf polygons object that can be used for spatial temporal analysis of moving polygons as described in the paper Robertson et al. (2007).

Usage

stamp(T1, T2, dc = 0, direction = FALSE, distance = FALSE, ...)

Arguments

`T1`	a `sf` polygons object of polygons from time 1.
`T2`	a `sf` polygons object of polygons from time 2.
`dc`	spatial distance threshold for determining groupings (see Details) in appropriate units.
`direction`	logical, whether or not to perform directional analysis. See documentation for `stamp.direction` for further details.
`distance`	logical, whether or not to perform distance analysis. See documentation for `stamp.distance` for further details.
`...`	additional parameters to be passed to functions if `direction`, or `distance` are set to `TRUE`.

Details

The stamp function can be used to perform spatial temporal analysis of moving polygons (STAMP) as outlined in the paper by Robertson et al., (2007). Polygon movement "groups" are delineated based on polygon connectedness defined by the distance threshold dc. That is, if polygon boundaries (in T1 or T2) are within distance dc of one another they will be designated to the same group. STAMP events are reported at four levels of increasing complexity:
LEV1 – disappearance (DISA), stable (STBL), and generation (GENA);
LEV2 – disappearance (DISA), contraction (CONT), stable (STBL), expansion (EXPN), and generation (GENR);
LEV3 – disappearance (DISA), T1 displacement (DISP1), convergence (CONV), concentration (CONC), contraction (CONT), stable (STBL), expansion (EXP), fragmentation (FRAG), divergence (DIV), T2 displacement (DISP2), and generation (GENR);
LEV4 – LEV4 is different from other levels. It is used to identify those groups where union (UNION), division (DIVISION), and both union and division (BOTH) events occur. These events occur when there are more than one stable event in a group. Groups with one or no stable events receive an NA value for LEV4.
See Robertson et al. (2007; especially Figure 1) for complete descriptions of all STAMP movement event types.

Note also that there must be a unique ID of each polygon, the function uses the row.names of the polygon objects. Modify the row.names accordingly if you wish to use an alternative ID label.

Value

This function returns a sf polygons object with the following data columns:

`ID1`	Polygon ID from T1 polygons; `NA` if it did not exist,
`ID2`	Polygon ID from T2 polygons; `NA` if it did not exist,
`LEV1`	Level 1 STAMP designation,
`LEV2`	Level 2 STAMP designation,
`LEV3`	Level 3 STAMP designation,
`LEV4`	Level 4 STAMP designation,
`GROUP`	Group ID signifying group membership,
`AREA`	Polygon area in appropriate areal units,
`--`	(optional) Additional columns from directional analysis if `direction = TRUE`,
`--`	(optional) Additional columns from distance analysis if `distance = TRUE`,

References

Robertson, C., Nelson, T., Boots, B., and Wulder, M. (2007) STAMP: Spatial-temporal analysis of moving polygons. Journal of Geographical Systems, 9:207-227.