Display an elevation GeoTIFF with a color map.
A GeoTIFF that contains elevation data in 32-bit floating point values. You can visualize the dataset in the following ways: as an elevation layer with or without a color map, as a color layer compressed to 8-bit using Interpretation.CompressTo8Bit, and as a color layer with a ColorMap.
import colormap from "colormap";
import { Color } from "three";
import { MapControls } from "three/examples/jsm/controls/MapControls.js";
import Extent from "@giro3d/giro3d/core/geographic/Extent.js";
import GeoTIFFSource from "@giro3d/giro3d/sources/GeoTIFFSource.js";
import Instance from "@giro3d/giro3d/core/Instance.js";
import ColorLayer from "@giro3d/giro3d/core/layer/ColorLayer.js";
import ElevationLayer from "@giro3d/giro3d/core/layer/ElevationLayer.js";
import Interpretation from "@giro3d/giro3d/core/layer/Interpretation.js";
import Map from "@giro3d/giro3d/entities/Map.js";
import Inspector from "@giro3d/giro3d/gui/Inspector.js";
import ColorMap, { ColorMapMode } from "@giro3d/giro3d/core/layer/ColorMap.js";
function makeColorRamp(
preset,
discrete = false,
invert = false,
mirror = false,
) {
let nshades = discrete ? 10 : 256;
// eslint-disable-next-line no-undef
const values = colormap({ colormap: preset, nshades });
// eslint-disable-next-line no-undef
const colors = values.map((v) => new Color(v));
if (invert) {
colors.reverse();
}
if (mirror) {
const mirrored = [...colors, ...colors.reverse()];
return mirrored;
}
return colors;
}
function bindDropDown(id, onChange) {
const element = document.getElementById(id);
if (!(element instanceof HTMLSelectElement)) {
throw new Error(
"invalid binding element: expected HTMLSelectElement, got: " +
element.constructor.name,
);
}
element.onchange = () => {
onChange(element.value);
};
const callback = (v) => {
element.value = v;
onChange(element.value);
};
return [callback, element.value, element];
}
const extent = new Extent(
"EPSG:3857",
-13581040.085,
-13469591.026,
5780261.83,
5942165.048,
);
const instance = new Instance({
target: "view",
crs: extent.crs,
});
instance.view.camera.position.set(-13656319, 5735451, 88934);
const controls = new MapControls(instance.view.camera, instance.domElement);
controls.enableDamping = true;
controls.dampingFactor = 0.2;
controls.target.set(-13545408, 5837154, 0);
instance.view.setControls(controls);
const map = new Map({
extent,
backgroundColor: "gray",
hillshading: true,
});
instance.add(map);
// Use an elevation COG with nodata values
const source = new GeoTIFFSource({
// https://www.sciencebase.gov/catalog/item/632a9a9ad34e71c6d67b95a3
url: "https://3d.oslandia.com/cog_data/COG_EPSG3857_USGS_13_n47w122_20220919.tif",
crs: extent.crs,
});
const min = 263;
const max = 4347;
// Display it as elevation and color
const viridis = new ColorMap(
makeColorRamp("viridis"),
min,
max,
ColorMapMode.Elevation,
);
const magma = new ColorMap(
makeColorRamp("magma"),
min,
max,
ColorMapMode.Elevation,
);
// Attach the inspector
Inspector.attach("inspector", instance);
function updateMode(value) {
map.removeLayer(map.getLayers()[0]);
switch (value) {
case "elevation-colormap":
map.addLayer(
new ElevationLayer({
name: value,
extent,
source,
colorMap: viridis,
minmax: { min, max },
}),
);
break;
case "elevation":
map.addLayer(
new ElevationLayer({
name: value,
extent,
source,
minmax: { min, max },
}),
);
break;
case "8bit":
map.addLayer(
new ColorLayer({
name: value,
extent,
source,
interpretation: Interpretation.CompressTo8Bit(min, max),
}),
);
break;
case "colormap":
map.addLayer(
new ColorLayer({
name: value,
extent,
source,
colorMap: magma,
}),
);
break;
default:
break;
}
instance.notifyChange(map);
}
bindDropDown("mode", updateMode);
updateMode("elevation");
<!doctype html>
<html lang="en">
<head>
<title>Elevation GeoTIFF</title>
<meta charset="UTF-8" />
<meta name="name" content="cog_elevation" />
<meta
name="description"
content="Display an elevation GeoTIFF with a color map."
/>
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<link rel="icon" href="https://giro3d.org/images/favicon.svg" />
<link
href="https://giro3d.org/assets/bootstrap-custom.css"
rel="stylesheet"
/>
<script src="https://giro3d.org/assets/bootstrap.bundle.min.js"></script>
<link
rel="stylesheet"
type="text/css"
href="https://giro3d.org/next/css/example.css"
/>
</head>
<body>
<div id="view" class="m-0 p-0 w-100 h-100"></div>
<div
id="inspector"
class="position-absolute top-0 start-0 mh-100 overflow-auto"
></div>
<div class="side-pane-with-status-bar">
<!-- Top color layer -->
<div class="card">
<div class="card-body">
<div class="input-group">
<span class="input-group-text flex-grow-1">Read COG as</span>
<select
class="btn btn-outline-primary btn-sm"
id="mode"
autocomplete="off"
>
<option selected value="elevation">Elevation layer</option>
<option value="elevation-colormap">
Elevation layer (with colormap)
</option>
<option value="8bit">Color layer (compressed to 8-bit)</option>
<option value="colormap">Color layer (with colormap)</option>
</select>
</div>
</div>
</div>
</div>
<script type="module" src="index.js"></script>
<script>
/* activate popovers */
const popoverTriggerList = [].slice.call(
document.querySelectorAll('[data-bs-toggle="popover"]'),
);
popoverTriggerList.map(
// bootstrap is used as script in the template, disable warning about undef
// eslint-disable-next-line no-undef
(popoverTriggerEl) =>
new bootstrap.Popover(popoverTriggerEl, {
trigger: "hover",
placement: "left",
content: document.getElementById(
popoverTriggerEl.getAttribute("data-bs-content"),
).innerHTML,
html: true,
}),
);
</script>
</body>
</html>
{
"name": "cog_elevation",
"dependencies": {
"colormap": "^2.3.2",
"@giro3d/giro3d": "git+https://gitlab.com/giro3d/giro3d.git"
},
"devDependencies": {
"vite": "^3.2.3"
},
"scripts": {
"start": "vite",
"build": "vite build"
}
}