# API to interpolate positions along a Polyline?

**URL:** <https://community.cesium.com/t/api-to-interpolate-positions-along-a-polyline/4393>\
**Category:** CesiumJS\
**Created:** [July 18, 2016, 6:47pm UTC](https://community.cesium.com/t/api-to-interpolate-positions-along-a-polyline/4393 "2016-07-18T18:47:52Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![David\_Whipps](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/david_whipps/32/3522_2.png) [@David\_Whipps](https://community.cesium.com/u/David_Whipps)\
**Post date:** [July 18, 2016, 6:47pm UTC](https://community.cesium.com/t/api-to-interpolate-positions-along-a-polyline/4393/1 "2016-07-18T18:47:52Z")

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I have a simple polyline entity defined by two Cartesian3 vectors.

Is there an easy API to interpolate positions along that polyline?

Thanks

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**Author:** ![AnG3L](https://avatars.discourse-cdn.com/v4/letter/a/e19adc/32.png) [@AnG3L](https://community.cesium.com/u/AnG3L)\
**Post date:** [July 19, 2016, 1:16am UTC](https://community.cesium.com/t/api-to-interpolate-positions-along-a-polyline/4393/2 "2016-07-19T01:16:01Z")

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Hi David,

Did you check this Sandcastle example ([https://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Interpolation.html&label=Showcases](https://cesiumjs.org/Cesium/Apps/Sandcastle/index.html?src=Interpolation.html&label=Showcases)) ?

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<div class="post-metadata">

**Author:** ![David\_Whipps](https://sea2.discourse-cdn.com/cesium/user_avatar/community.cesium.com/david_whipps/32/3522_2.png) [@David\_Whipps](https://community.cesium.com/u/David_Whipps)\
**Post date:** [July 19, 2016, 12:59pm UTC](https://community.cesium.com/t/api-to-interpolate-positions-along-a-polyline/4393/3 "2016-07-19T12:59:22Z")

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Thanks AnG3L, but I actually found the answer to my own question. Use an [EllipsoidGeodesic](http://cesiumjs.org/Cesium/Build/Documentation/EllipsoidGeodesic.html?classFilter=EllipsoidGeodesic), which provides a method called interpolateUsingFraction() giving me exactly what I want.