# IfcLinearPlacement.PlacementMeasuredAlong - the curves location is not clear

**URL:** <https://forums.buildingsmart.org/t/ifclinearplacement-placementmeasuredalong-the-curves-location-is-not-clear/2898>\
**Category:** Infra-Common Schema\
**Created:** [August 14, 2020, 3:32am UTC](https://forums.buildingsmart.org/t/ifclinearplacement-placementmeasuredalong-the-curves-location-is-not-clear/2898 "2020-08-14T03:32:01Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![igor.sokolov](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/igor.sokolov/32/25_2.png) [@igor.sokolov](https://forums.buildingsmart.org/u/igor.sokolov)\
**Post date:** [August 14, 2020, 3:32am UTC](https://forums.buildingsmart.org/t/ifclinearplacement-placementmeasuredalong-the-curves-location-is-not-clear/2898/1 "2020-08-14T03:32:01Z")

</div>

IfcLinearPlacement.PlacementMeasuredAlong references to curve, but what coordinate system is used for the curve?

Should I search IfcProduct that has the curve in Representations and use ObjectPlacement to have answer? Or should I trust PlacementRelTo?  
They can mismatch.