<script setup> import * as d3 from "d3"; import UsMap from "../components/UsMap.vue"; import WorldMap from "../components/WorldMap.vue"; const width = 688; const height = 400; </script>

Conic projections

Conic projections project the sphere onto a cone, and then unroll the cone onto the plane. Conic projections have two standard parallels.

conic.parallels(parallels) {#conic_parallels}

Source · The two standard parallels that define the map layout in conic projections.

geoConicConformal() {#geoConicConformal}

<a href="https://observablehq.com/@d3/conic-conformal" target="_blank" style="color: currentColor;"><WorldMap resolution="50m" :projection='d3.geoConicConformal().parallels([35, 65]).rotate([-20, 0]).scale(width * 0.55).center([0, 52]).translate([width / 2, height / 2]).clipExtent([[-1, -1], [width + 1, height + 1]]).precision(0.2)' /></a>

Source · The conic conformal projection. The parallels default to [30°, 30°] resulting in flat top.

<!-- <a href="#geoConicConformalRaw" name="geoConicConformalRaw">#</a> d3.<b>geoConicConformalRaw</b>(<i>phi0</i>, <i>phi1</i>) -->

geoConicEqualArea() {#geoConicEqualArea}

<a href="https://observablehq.com/@d3/conic-conformal" target="_blank" style="color: currentColor;"><WorldMap resolution="50m" :projection='d3.geoConicEqualArea().parallels([35, 65]).rotate([-20, 0]).scale(width * 0.55).center([0, 52]).translate([width / 2, height / 2]).clipExtent([[-1, -1], [width + 1, height + 1]]).precision(0.2)' /></a>

Source · The Albers’ equal-area conic projection.

<!-- <a href="#geoConicEqualAreaRaw" name="geoConicEqualAreaRaw">#</a> d3.<b>geoConicEqualAreaRaw</b>(<i>phi0</i>, <i>phi1</i>) -->

geoConicEquidistant() {#geoConicEquidistant}

<a href="https://observablehq.com/@d3/conic-equidistant" target="_blank" style="color: currentColor;"><WorldMap resolution="50m" :projection='d3.geoConicEquidistant().parallels([35, 65]).rotate([-20, 0]).scale(width * 0.55).center([0, 52]).translate([width / 2, height / 2]).clipExtent([[-1, -1], [width + 1, height + 1]]).precision(0.2)' /></a>

Source · The conic equidistant projection.

<!-- <a href="#geoConicEquidistantRaw" name="geoConicEquidistantRaw">#</a> d3.<b>geoConicEquidistantRaw</b>(<i>phi0</i>, <i>phi1</i>) -->

geoAlbers() {#geoAlbers}

<a href="https://observablehq.com/@d3/u-s-map" target="_blank" style="color: currentColor;"><UsMap :projection='d3.geoAlbers().scale(1300 / 975 * width * 0.8).translate([width / 2, height / 2])' /></a>

Source · The Albers’ equal area-conic projection. This is a U.S.-centric configuration of geoConicEqualArea.

geoAlbersUsa() {#geoAlbersUsa}

<a href="https://observablehq.com/@d3/u-s-map" target="_blank" style="color: currentColor;"><UsMap :projection='d3.geoAlbersUsa().scale(1300 / 975 * width * 0.8).translate([width / 2, height / 2])' /></a>

Source · This is a U.S.-centric composite projection of three geoConicEqualArea projections: geoAlbers is used for the lower forty-eight states, and separate conic equal-area projections are used for Alaska and Hawaii. The scale for Alaska is diminished: it is projected at 0.35× its true relative area. See Albers USA with Territories for an extension to all US territories, and d3-composite-projections for more examples.

The constituent projections have fixed clip, center and rotation, and thus this projection does not support projection.center, projection.rotate, projection.clipAngle, or projection.clipExtent.