Plot ellipses at grid intersection points, as a method for indicating the distortion inherent in the projection . (Each ellipse is drawn with 64 segments.)
numeric vector of length 2, specifying the increment in
longitude and latitude for the grid. Indicatrices are drawn at e.g.
numerical scale factor for ellipses. This is multiplied by
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 , but should also be self-explanatory.
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
Other functions related to maps:
1 2 3 4 5 6 7 8 9 10
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