mapTissot {oce} | R Documentation |
Plot ellipses at grid intersection points, as a method for indicating the distortion inherent in the projection [1]. (Each ellipse is drawn with 64 segments.)
mapTissot(grid = rep(15, 2), scale = 0.2, crosshairs = FALSE, ...)
grid |
numeric vector of length 2, specifying the increment in
longitude and latitude for the grid. Indicatrices are drawn at e.g.
longitudes |
scale |
numerical scale factor for ellipses. This is multiplied by
|
crosshairs |
logical value indicating whether to draw constant-latitude
and constant-longitude crosshairs within the ellipses. (These are drawn
with 10 line segments each.) This can be helpful in cases where it is
not desired to use |
... |
extra arguments passed to plotting functions, e.g.
|
The purpose and interpretation are outlined in [1], but should also be self-explanatory.
Dan Kelley
1. Snyder, John P., 1987. Map Projections: A Working Manual. USGS Professional Paper: 1395 (available at pubs.usgs.gov/pp/1395/report.pdf).
A map must first have been created with mapPlot
.
Other functions related to maps: lonlat2map
,
lonlat2utm
, map2lonlat
,
mapArrows
, mapAxis
,
mapContour
,
mapDirectionField
, mapGrid
,
mapImage
, mapLines
,
mapLocator
,
mapLongitudeLatitudeXY
,
mapPlot
, mapPoints
,
mapPolygon
, mapScalebar
,
mapText
, oceCRS
,
shiftLongitude
, utm2lonlat
## Not run: library(oce) data(coastlineWorld) par(mfrow=c(1, 1), mar=c(2, 2, 1, 1)) p <- "+proj=aea +lat_1=10 +lat_2=60 +lon_0=-45" mapPlot(coastlineWorld, projection=p, col="gray", longitudelim=c(-90,0), latitudelim=c(0, 50)) mapTissot(c(15, 15), col='red') ## End(Not run)