A contour map overlays isolines (lines of equal value) onto a geographic basemap, visualizing continuous spatial data such as elevation, temperature, or atmospheric pressure across real-world coordinates. Unlike basic contour plots that use abstract x/y coordinates, this plot anchors contours to latitude/longitude positions with geographic context like coastlines, borders, or terrain. It combines the precision of isoline visualization with spatial awareness, making it ideal for meteorological, topographic, and environmental applications.
# anyplot.ai
# contour-map-geographic: Contour Lines on Geographic Map
# Library: makie 0.21.9 | Julia 1.11.9
# Quality: 93/100 | Created: 2026-09-01
using CairoMakie
using Colors
using Random
Random.seed!(42)
# Theme tokens
const THEME = get(ENV, "ANYPLOT_THEME", "light")
const PAGE_BG = THEME == "light" ? colorant"#FAF8F1" : colorant"#1A1A17"
const ELEVATED_BG = THEME == "light" ? colorant"#FFFDF6" : colorant"#242420"
const INK = THEME == "light" ? colorant"#1A1A17" : colorant"#F0EFE8"
const INK_SOFT = THEME == "light" ? colorant"#4A4A44" : colorant"#B8B7B0"
const ANYPLOT_SEQ = cgrad([colorant"#009E73", colorant"#4467A3"])
# Data — synthetic elevation grid over the Cascade Range stratovolcanoes (Washington, USA)
const PEAKS = [
(name = "Mount Baker", lat = 48.7768, lon = -121.8144, elev = 3286.0),
(name = "Glacier Peak", lat = 48.1112, lon = -121.1141, elev = 3213.0),
(name = "Mount Rainier", lat = 46.8529, lon = -121.7604, elev = 4392.0),
(name = "Mount Adams", lat = 46.2024, lon = -121.4906, elev = 3743.0),
(name = "Mount St. Helens", lat = 46.1912, lon = -122.1944, elev = 2549.0),
]
const lon = range(-123.6, -120.7; length = 72)
const lat = range(45.9, 49.1; length = 60)
# Rolling foothill baseline (west→east) plus a Gaussian bump per named summit
const z = [
250.0 + 350.0 * clamp((lo + 123.2) / 2.5, 0.0, 1.0) +
sum((p.elev - 380.0) * exp(-(((lo - p.lon) / 0.22)^2 + ((la - p.lat) / 0.22)^2)) for p in PEAKS)
for lo in lon, la in lat
]
const LEVELS = collect(0.0:500.0:4500.0)
const LABEL_LEVELS = collect(0.0:500.0:2000.0) # index contours — the tight rings near each
# summit stay unlabeled since the peak marker
# already states the exact elevation there
# Puget Sound coastline: a wavy west boundary marking land vs. water
const lat_vec = collect(lat)
const coast_lon = @. -123.35 + 0.20 * sin(2.3 * (lat_vec - 45.9)) - 0.05 * cos(4.1 * (lat_vec - 45.9))
# Plot
fig = Figure(
size = (1600, 900),
fontsize = 14,
backgroundcolor = PAGE_BG,
)
ax = Axis(
fig[1, 1];
title = "Cascade Range Volcanoes · contour-map-geographic · julia · makie · anyplot.ai",
titlesize = 17,
titlecolor = INK,
xlabel = "Longitude",
ylabel = "Latitude",
xlabelsize = 14,
ylabelsize = 14,
xlabelcolor = INK,
ylabelcolor = INK,
xticklabelsize = 12,
yticklabelsize = 12,
xticklabelcolor = INK_SOFT,
yticklabelcolor = INK_SOFT,
xtickcolor = INK_SOFT,
ytickcolor = INK_SOFT,
xtickformat = vs -> ["$(round(abs(v), digits = 1))°W" for v in vs],
ytickformat = vs -> ["$(round(v, digits = 1))°N" for v in vs],
backgroundcolor = PAGE_BG,
topspinevisible = false,
rightspinevisible = false,
leftspinecolor = INK_SOFT,
bottomspinecolor = INK_SOFT,
xgridcolor = RGBAf(INK.r, INK.g, INK.b, 0.12),
ygridcolor = RGBAf(INK.r, INK.g, INK.b, 0.12),
limits = (minimum(lon), maximum(lon), minimum(lat), maximum(lat)),
)
# Filled elevation contours
cf = contourf!(ax, lon, lat, z; levels = LEVELS, colormap = ANYPLOT_SEQ)
# Contour lines at every 500 m
contour!(ax, lon, lat, z; levels = LEVELS, color = INK, linewidth = 1.0)
# Index contours (every 500 m up to 2000 m) carry the value labels — the
# tighter rings closer to each summit are left unlabeled to avoid crowding
# the peak-name labels below
contour!(ax, lon, lat, z;
levels = LABEL_LEVELS,
color = INK,
linewidth = 1.4,
labels = true,
labelsize = 11,
labelcolor = INK,
labelformatter = level -> "$(Int(round(level))) m",
)
# Mask the water west of the coastline, then stroke the shoreline itself
west_edge = minimum(lon) - 0.3
water_poly = vcat(
[Point2f(coast_lon[i], lat_vec[i]) for i in eachindex(lat_vec)],
[Point2f(west_edge, lat_vec[i]) for i in reverse(eachindex(lat_vec))],
)
poly!(ax, water_poly; color = PAGE_BG, strokewidth = 0)
lines!(ax, coast_lon, lat_vec; color = INK_SOFT, linewidth = 2.5, label = "Puget Sound coastline")
# Volcanic summits, labeled with elevation
scatter!(ax, [p.lon for p in PEAKS], [p.lat for p in PEAKS];
marker = :utriangle,
markersize = 16,
color = INK,
strokewidth = 1.5,
strokecolor = PAGE_BG,
label = "Volcanic peak",
)
for p in PEAKS
text!(ax, p.lon, p.lat;
text = "$(p.name) ($(Int(round(p.elev))) m)",
fontsize = 12,
font = :bold,
color = INK,
strokecolor = PAGE_BG,
strokewidth = 1.3,
align = (:center, :bottom),
offset = (0, 14),
)
end
axislegend(ax;
position = :rb,
backgroundcolor = ELEVATED_BG,
labelcolor = INK,
framecolor = INK_SOFT,
labelsize = 11,
)
Colorbar(fig[1, 2], cf;
label = "Elevation (m)",
labelcolor = INK,
labelsize = 14,
tickcolor = INK_SOFT,
ticklabelcolor = INK_SOFT,
ticklabelsize = 12,
ticks = LEVELS,
width = 20,
)
# Save
save("plot-$(THEME).png", fig; px_per_unit = 2)
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/contour-map-geographic/makie/code. Any spec id and library id listed in llms-full.txt fit the same URL shape; every URL below is complete and callable.
{
"spec_id": "contour-map-geographic",
"language": "julia",
"library": "makie",
"page": "https://anyplot.ai/contour-map-geographic/julia/makie",
"hub": "https://anyplot.ai/contour-map-geographic",
"code_json": "https://api.anyplot.ai/specs/contour-map-geographic/makie/code",
"spec_json": "https://api.anyplot.ai/specs/contour-map-geographic",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/contour-map-geographic/julia/makie/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/contour-map-geographic/julia/makie/plot-dark.png",
"quality_score": 93.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Contour Lines on Geographic Map on anyplot.ai.