diff --git a/edm4eic.yaml b/edm4eic.yaml
index e245791..fd22fef 100644
--- a/edm4eic.yaml
+++ b/edm4eic.yaml
@@ -336,8 +336,22 @@ datatypes:
       - float             edep              // Energy deposit in this hit [GeV]
       - float             edepError         // Error on the energy deposit [GeV]
 
+  edm4eic::Measurement2D:
+    Description: "2D measurement (on an arbitrary surface)"
+    Author: "W. Deconinck"
+    Members:
+      - uint64_t          surface           // Surface for bound coordinates (geometryID)
+      - edm4hep::Vector2f loc               // 2D location on surface
+      - float             time              // Measurement time
+      - edm4eic::Cov3f    covariance        // Covariance on location and time
+    VectorMembers:
+      - float             weights           // Weight for each of the hits, mirrors hits array
+    OneToManyRelations:
+      - edm4eic::TrackerHit hits            // Hits in this measurement (single or clustered)
+
+      
   edm4eic::Trajectory:
-    Description: "Raw trajectory from the tracking algorithm"
+    Description: "Raw trajectory from the tracking algorithm. What is called hit here is 2d measurement indeed."
     Author: "S. Joosten, S. Li"
     Members:
       - uint32_t          type              // 0 (does not have good track fit), 1 (has good track fit)
@@ -353,8 +367,8 @@ datatypes:
       - float             outlierChi2       // Chi2 for each of the outliers
     OneToManyRelations:
       - edm4eic::TrackParameters trackParameters // Associated track parameters, if any
-      - edm4eic::TrackerHit  measurementHits // Measurement hits used in this trajectory
-      - edm4eic::TrackerHit  outlierHits     // Outlier hits not used in this trajectory
+      - edm4eic::Measurement2D  measurementHits // Measurement hits used in this trajectory
+      - edm4eic::Measurement2D  outlierHits     // Outlier hits not used in this trajectory
   
   edm4eic::TrackParameters:
     Description: "ACTS Bound Track parameters"