The function stamp.distance can be used to compute various measures of distance
between polygon events and groups. In turn, distance measurements can be used to estimate the velocity
of polygon movement.
stamp.distance(stmp, dist.mode = "Centroid", group = FALSE)Appropriately named columns (e.g., CENDIST or HAUSDIST) in the stamp sf
object. Distances are in meters.
a sf object generated from the stamp function.
Character determining the method by which polygon distances are computed. If "Centroid"
then the centroid distance is calculated, if "Hausdorff" then the discrete Hausdorff distance
is calculated; see Details.
logical indicating whether distances should be computed from the T1 polygon to each individual
stamp event (group = FALSE -- the default), or whether T2 polygons should combined (through a spatial
union) in order to compute the measure of distance for each stamp group (group = TRUE)
stamp.distance computes distance between polygon sets based on either centroid or
Hausdorff distance calculations. Centroid distance is simply the distance from the centroid
of all T1 polygons (combined) to each stamp event (group = FALSE), or to the union of
all T2 polygons within a group (group = TRUE), in the second case, all events within a group
are given an identical distance value.
The Hausdorff distance calculation uses the Hausdorff distance, as
programmed in the function st_distance. A value of par = 0.1 is used
to increase the precision of this measurement -- see help(st_distance). The returned distance
is then the Hausdorff distance of all T1 polygons (combined) to each stamp event (group = FALSE),
or to the union of all T2 polygons within a group (group = TRUE), in the second case, all events
within a group are given an identical distance value.
All distance calculations are computed in meters using the geographical projection WGS84.
Hausdorff Distance: https://en.wikipedia.org/wiki/Hausdorff_distance
stamp stamp.direction