Metview Macro Library function. Used to plot a circle with a given radius in km onto a non-cylindrical map projection. Internally, the circle is split into a number of segments and the returned result is an Input Visualiser object which can be passed to the plot() command along with an optional Graph Plotting object.
definition mvl_geocircle(lat : number, lon : number,radius : number, resolution : number)
The first three parameters specify the centre and the radius (in km) of the circle. Parameter resolution defines the number of line segments to use to make up the circle.
# Metview Macro
# **************************** LICENSE START ***********************************
#
# Copyright 2017 ECMWF. This software is distributed under the terms
# of the Apache License version 2.0. In applying this license, ECMWF does not
# waive the privileges and immunities granted to it by virtue of its status as
# an Intergovernmental Organization or submit itself to any jurisdiction.
#
# ***************************** LICENSE END ************************************
# ---------------------------------------------------------------
# Tags: mvl,coast
# Title: Geocircle on Map
# Description: Demonstrates how to plot a circle on any map
# projection using the Macro Library function
# mvl_geocircle.
# ---------------------------------------------------------------
# set up the shaded coastlines
land_sea_shade = mcoast
(
map_coastline_land_shade : "on",
map_coastline_land_shade_colour : "RGB(0.98,0.95,0.82)",
map_coastline_sea_shade : "on",
map_coastline_sea_shade_colour : "RGB(0.85,0.93,1)"
)
# define the geographic view
view = geoview
(
map_projection : "polar_stereographic",
map_area_definition : "corners",
area : [-5,-30,10,84], # S,W,N,E
coastlines : land_sea_shade
)
# define the radius of the circles (in km)
circle_radius = 200
# the circle will be made up of this many segments
circle_resolution = 80
# define the centres of the circles
latPos=[58,48,38,28,18,8]
lonPos=[-20,-8,4,16,28,40]
# build the plot the finition of the circles
pltLst=nil
for i=1 to count(latPos) do
# define the cirle around the specifed coordinates
iv_circle = mvl_geocircle(latPos[i],lonPos[i],circle_radius,circle_resolution)
# define the plotting attributes for the circle
graph_circle = mgraph
(
graph_line_colour : "red",
graph_line_thickness : "4",
graph_line_style : 'solid'
)
# collect the plot definitions into a list
pltLst=pltLst & [iv_circle,graph_circle]
end for
# define the output media
to_pdf_file = pdf_output
(
output_name : "plot" # extension is added automatically
)
# check the runmode and decide which media to put the plot to
mode = runmode()
if mode = "execute" or mode = "batch" then
setoutput(to_pdf_file)
end if
# plot the circles on the map
plot(view, pltLst)
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