diff --git a/CITATION.cff b/CITATION.cff
index 5f9736e..f28ca11 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -2,7 +2,7 @@ cff-version: 1.2.0
 type: software
 license: MIT
 title: VPTS CSV
-version: 1.0
+version: 1.1
 abstract: >-
   Data exchange format for biological signals detected by
   weather radars.
@@ -21,7 +21,7 @@ authors:
     affiliation: Cornell Lab of Ornithology
 repository-code: https://github.com/aloftdata/vpts-csv
 url: https://aloftdata.eu/vpts-csv
-date-released: '2023-12-18'
+date-released: '2025-11-20'
 keywords:
 - data exchange format
 - frictionlessdata
diff --git a/LICENSE b/LICENSE
index a7df74c..298aecd 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2023 Research Institute for Nature and Forest (INBO)
+Copyright (c) 2025 Research Institute for Nature and Forest (INBO)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/vpts-csv-table-schema.json b/vpts-csv-table-schema.json
index c62720f..3deea05 100644
--- a/vpts-csv-table-schema.json
+++ b/vpts-csv-table-schema.json
@@ -23,8 +23,8 @@
     {
       "name": "height",
       "nameAlternatives": ["HGHT", "bin_lower"],
-      "description": "Lower bound of the altitude bin in m above sea level.",
-      "type": "integer",
+      "description": "Lower bound of the altitude bin in m, measured from `height_reference`.",
+      "type": "number",
       "example": "600",
       "constraints": {
         "required": true,
@@ -32,6 +32,20 @@
         "maximum": 25000
       }
     },
+    {
+      "name": "height_reference",
+      "description": "Reference for `height`. `\"sea\"` and `\"antenna\"` are used for heights defined from mean sea level and radar antenna respectively, resulting in horizontal altitude bins. `\"terrain\"` is used for heights that are calculated relative to a digital elevation model for each pixel in the volume.",
+      "type": "string",
+      "example": "sea",
+      "constraints": {
+        "required": true,
+        "enum": [
+          "sea",
+          "antenna",
+          "terrain"
+        ]
+      }
+    },
     {
       "name": "u",
       "description": "Ground speed component west to east in m/s.",
@@ -228,7 +242,7 @@
     {
       "name": "radar_height",
       "description": "Height of the center of the radar antenna in m above sea level. Constant for all records from the same `radar`.",
-      "type": "integer",
+      "type": "number",
       "example": "519",
       "constraints": {
         "required": true,