nowrapSpatialLines: Split SpatialLines components at offset

In maptools: Tools for Handling Spatial Objects

Split SpatialLines components at offset

Description

When recentering a world map, most often from the "Atlantic" view with longitudes with range -180 to 180, to the "pacific" view with longitudes with range 0 to 360, lines crossing the offset (0 for this conversion) get stretched horizonally. This function breaks Line objects at the offset (usually Greenwich), inserting a very small gap, and reassembling the Line objects created as Lines. The rgeos package is required to use this function.

Usage

nowrapSpatialLines(obj, offset = 0, eps = rep(.Machine$double.eps^(1/2.5), 2))

Arguments

obj	A Spatial Lines object
offset	default 0, untried for other values
eps	vector of two fuzz values, both default 2.5 root of double.eps

Value

A Spatial Lines object

Author(s)

Roger Bivand

See Also

recenter-methods, nowrapSpatialPolygons

Examples

Sl <- SpatialLines(list(Lines(list(Line(cbind(sin(seq(-4,4,0.4)),
 seq(1,21,1)))), "1")), proj4string=CRS("+proj=longlat +ellps=WGS84"))
summary(Sl)
if (require(rgeos)) {
nwSL <- nowrapSpatialLines(Sl)
summary(nwSL)
if(require(maps)) {
worldmap <- map("world", plot=FALSE)
worldmapLines <- map2SpatialLines(worldmap, proj4string=CRS("+proj=longlat +datum=WGS84"))
bbox(worldmapLines)
t0 <- nowrapSpatialLines(worldmapLines, offset=180)
bbox(t0)
}
}

maptools documentation built on July 26, 2023, 5:38 p.m.