scaleBar {OSMscale}

scalebar for OSM plots

Description

Add a scalebar to default or (UTM)-projected OpenStreetMap plots

Usage

scaleBar(
  map,
  x = 0.1,
  y = 0.9,
  length = 0.4,
  abslen = NA,
  unit = c("km", "m", "mi", "ft", "yd"),
  label = unit,
  type = c("bar", "line"),
  ndiv = NA,
  field = "rect",
  fill = NA,
  adj = c(0.5, 1.5),
  cex = par("cex"),
  col = c("black", "white"),
  targs = NULL,
  lwd = 7,
  lend = 1,
  bg = "transparent",
  mar = c(2, 0.7, 0.2, 3),
  ...
)

Arguments

map

Map object with map$tiles[[1]]$projection to get the projection from.

x, y

Relative position of left end of scalebar. DEFAULT: 0.1, 0.9

length

Approximate relative length of bar. DEFAULT: 0.4

abslen

Absolute length in units. DEFAULT: NA (computed internally from length)

unit

Unit for computation and label. Possible: kilometer, meter, miles, feet, yards. DEFAULT: "km"

label

Unit label in plot. DEFAULT: unit

type

Scalebar type: simple 'line' or classical black & white 'bar'. DEFAULT: "bar"

ndiv

Number of divisions if type="bar". DEFAULT: NA (computed internally) Internal selection of ndiv is based on divisibility of abslen (modulo) with 1:6. For ties, preferation order is 5>4>3>2>6>1.

field, fill, adj, cex

Arguments passed to textField

col

Vector of (possibly alternating) colors passed to segments or rect. DEFAULT: c("black","white")

targs

List of further arguments passed to textField like font, col (to differ from bar color), etc. DEFAULT: NULL

lwd, lend

Line width and end style passed to segments. DEFAULT: 5,1, which works well in pdf graphics.

bg

Background color, e.g. addAlpha(White). DEFAULT: "transparent" to suppress background.

mar

Background margins approximately in letter width/height. DEFAULT: c(2,0.7,0.2,3)

...

Further arguments passed to segments like lty. (Color for segments is the first value of col). Passed to rect if type="bar", like lwd.

Details

scaleBar gets the right distance in the default mercator projected maps. There, the axes are not in meters, but rather ca 0.7m units (for NW Germany area maps with 20km across). Accordingly, other packages plot wrong bars, see the last example section.

Value

invisible: coordinates of scalebar and label

Author(s)

Berry Boessenkool, [e-mail], Jun 2016

See Also

pointsMap, projectPoints

Examples

plot(0:10, 40:50, type="n", asp=1) # Western Europe in lat-long
map <- list(tiles=list(dummy=list(projection=pll())),
            bbox=list(p1=par("usr")[c(1,4)], p2=par("usr")[2:3]) )
scaleBar(map)

if(interactive()){
d <- data.frame(long=c(12.95, 12.98, 13.22, 13.11), lat=c(52.40,52.52, 52.36, 52.45))
map <- pointsMap(lat,long,d, scale=FALSE, zoom=9)
coord <- scaleBar(map)  ; coord
scaleBar(map, bg=berryFunctions::addAlpha("white", 0.7))
scaleBar(map, 0.3, 0.05, unit="m", length=0.45, type="line")
scaleBar(map, 0.3, 0.5, unit="km", abslen=5, col=4:5, lwd=3)
scaleBar(map, 0.3, 0.8, unit="mi", col="red", targ=list(col="blue", font=2), type="line")

# I don't like subdivisions, but if you wanted them, you could use:
sb <- scaleBar(map, 0.12, 0.28, abslen=10, adj=c(0.5, -1.5)  )
scaleBar(map, 0.12, 0.28, abslen=4, adj=c(0.5, -1.5), 
         targs=list(col="transparent"), label="" )

# more lines for exact measurements in scalebar:
segments(x0=seq(sb["x1"], sb["x2"], len=21), y0=sb["y1"], y1=sb["y2"], col=8)
rect(xleft=sb["x1"], xright=sb["x2"], ybottom=sb["y1"], ytop=sb["y2"])
}

## Not run:  # don't download too many maps in R CMD check
d <- read.table(header=TRUE, sep=",", text="
lat, long
52.514687,  13.350012   # Berlin
51.503162,  -0.131082   # London
35.685024, 139.753365") # Tokio
map <- pointsMap(lat, long, d, zoom=2, abslen=5000, y=0.7)
scaleBar(map, y=0.5, abslen=5000)   # in mercator projections, scale bars are not
scaleBar(map, y=0.3, abslen=5000)   # transferable to other latitudes

map_utm <- pointsMap(lat, long, d[1:2,], proj=putm(long=d$long[1:2]),
                     zoom=4, y=0.7, abslen=500)
scaleBar(map_utm, y=0.5, abslen=500) # transferable in UTM projection
scaleBar(map_utm, y=0.3, abslen=500)

## End(Not run)

## Not run:  ## Too much downloading time, too error-prone
# Tests around the world
par(mfrow=c(1,2), mar=rep(1,4))
long <- runif(2, -180, 180) ;  lat <- runif(2, -90, 90)
long <- 0:50 ;  lat <- 0:50
map <- pointsMap(lat, long)
map2 <- pointsMap(lat, long, map=map, proj=putm(long=long))

## End(Not run)

## Not run:  ## excluded from tests to avoid package dependencies
berryFunctions::require2("SDMTools")
berryFunctions::require2("raster")
berryFunctions::require2("mapmisc")
par(mar=c(0,0,0,0))
map <- OSMscale::pointsMap(long=c(12.95, 13.22), lat=c(52.52, 52.36))
SDMTools::Scalebar(x=1443391,y=6889679,distance=10000)
raster::scalebar(d=10000, xy=c(1443391,6884254))
OSMscale::scaleBar(map, x=0.35, y=0.45, abslen=5)
library(mapmisc) # otherwise rbind for SpatialPoints is not found
mapmisc::scaleBar(pmap(map)@projargs, seg.len=10, pos="center", bg="transparent")

## End(Not run)