Storing and Retrieving Coordinates from CZML

CesiumJS
1

1. A concise explanation of the problem you’re experiencing.

I have a CZML file that define polylines. The coordinates for the polylines look like this…

polyline: {
positions: {
cartographicDegrees: [-1.87, -3.02, 0, -4.43, 1.28, 0]
},
material: {
solidColor: {
color: {
rgba: [255, 0, 0, 255]
}
}
},
width: 2,
clampToGround: true
}

``

I need to grab those coordinates to display them elsewhere on my GUI…

I sort out my polylines into an array and pick them up like this…

var pos = mylines[0].polyline.positions;

``

then I have two helper functions to convert the from cartesian coordinates and then place them in another array.

$.each( pos._value, function( key, value ) {
c3 = Cesium.Ellipsoid.WGS84.cartesianToCartographic(value)
c2 = parseCartographic(c3);
console.log("c2: " + c2);
cart.push(c2);
});

function parseCartographic(str) {
var res = str.toString().split(",");
var ret = “[” +res[0].replace("(","") + “,” + res[1].replace("(","") + “]”;
return ret ;
}

``

The cart variable comes out looking like this

**"cart: [[-0.030368728984701332, -0.05270894341022874],[0.01710422666954443, 0.03036872898470134]]"**



Why are the coordinates all jacked up?

2. A minimal code example. If you’ve found a bug, this helps us reproduce and repair it.

see above

3. Context. Why do you need to do this? We might know a better way to accomplish your goal.

I want to draw a line based on this first line I get.

4. The Cesium version you’re using, your operating system and browser.

1.47, Windows10, latest Firefox.

Any help you can provide would be appreciated. Thanks,

Jody

2

The values returned by cartesianToCartographic() are in radians not degrees. Here’s what I did.
var czml = [{

“id” : “document”,

“name” : “CZML Geometries: Polyline”,

“version” : “1.0”

}, {

“id” : “redLine”,

“name” : “Red line clamped to terain”,

“polyline” : {

“positions” : {

“cartographicDegrees” : [

-75, 35, 0,

-125, 35, 0

]

},

“material” : {

“solidColor” : {

“color” : {

“rgba” : [255, 0, 0, 255]

}

}

},

“width” : 5,

“clampToGround” : true

}

}];

var viewer = new Cesium.Viewer(‘cesiumContainer’);

var dataSourcePromise = Cesium.CzmlDataSource.load(czml);

dataSourcePromise.then(function(dataSource) {

viewer.dataSources.add(dataSource);

viewer.zoomTo(dataSource);

var entities = dataSource.entities.values;

for (var i = 0; i < entities.length; i++) {

var entity = entities[i];

var xyzArray = entity.polyline.positions.valueOf();

var llhArray = Cesium.Ellipsoid.WGS84.cartesianArrayToCartographicArray(xyzArray);

for (var j = 0; j < llhArray.length; j++) {

var llh = llhArray[j];

console.log(’(’ + llh.longitude * Cesium.Math.DEGREES_PER_RADIAN + ', ’ + llh.latitude * Cesium.Math.DEGREES_PER_RADIAN + ', ’ + llh.height + ‘)’);

}

}

});

``

Hope that helps.

Scott

3

Awesome. Thanks!!