[WIP] Dimensions extension

extensions/README.md

@@ -14,6 +14,7 @@ them they can create a shared extension and include it in the STAC repository.
 | Extension Name (Prefix)                                      | Scope            | Description                                                  |
 | ------------------------------------------------------------ | ---------------- | ------------------------------------------------------------ |
 | [Collection](stac-collection-spec.md) (`c`)                  | Item             | Provides a way to specify data fields that are common across a collection of STAC Items, so that each does not need to repeat all the same information. |
+| [Dimensions](dimensions/) (`dim`)                            | Dataset          | Allows to describe data with multiple dimensions (= axes), e.g. in meteorology. |
 | [EO](stac-eo-spec.md) (`eo`)                                 | Item             | Covers data that represents a snapshot of the earth for a single date and time. It could consist of multiple spectral bands in any part of the electromagnetic spectrum. Examples of EO data include sensors with visible bands, IR bands as well as SAR instruments. The extension provides common fields like bands, cloud cover, off nadir, sun angle + elevation, gsd and more. |
 | [Scientific](scientific/) (`sci`)                            | Catalog +Dataset | Scientific metadata is considered to be data that indicate from which publication a dataset originates and how the dataset itself should be cited or referenced. |
 | [Start end datetime](stac-start-end-datetime-spec.md) (`set`) | Item             | An extension to provide start and end datetime stamps in a consistent way. |

extensions/dimensions/README.md

@@ -0,0 +1,19 @@
+# STAC Dimensions Extension Spec
+
+This document explains the fields of the STAC Dimensions Extension (dim) to a STAC `Dataset`. Data can have different dimensions (= axes), e.g. in meteorology. The properties of these dimensions can be defined with this extension.
+
+## Dimensions Extension Description
+
+This is the field that extends the `Dataset` object:
+
+| Element          | Type                 | Name                      | Description                                                  |
+| ---------------- | -------------------- | ------------------------- | ------------------------------------------------------------ |
+| dim:dimensions          | [Dimension Object] | Dimensions               | Dimensions of the data. If the dimensions have an order, the order SHOULD be reflected in the order of the array. |
+
+### Dimension Object
+
+| Element | Type             | Name                | Description                                                  |
+| ------- | ---------------- | ------------------- | ------------------------------------------------------------ |
+| label   | string           | Label (required)    | Human-readable label for the dimension.                      |
+| unit    | string           | Unit of Measurement | Unit of measurement, preferably SI. ToDo: Any standard to express this, e.g. [UDUNITS](https://www.unidata.ucar.edu/software/udunits/) or this [dict](https://www.unc.edu/~rowlett/units/)? |
+| extent  | [number\|string] | Data Extent         | Specifies the extent of the data, i.e. the lower bound as the first element and the upper bound as the second element of the array. |

extensions/dimensions/example.json

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+{
+  "dim:dimensions": [
+    {
+      "label": "Longitude",
+      "unit": "°",
+      "extent": [-180, 180]
+    },
+    {
+      "label": "Latitude",
+      "unit": "°",
+      "extent": [-90, 90]
+    },
+    {
+      "label": "Temperature",
+      "unit": "°C",
+      "extent": [-20, 60]
+    },
+    {
+      "label": "Date",
+      "extent": ["2018-01-01T00:00:00Z", "2018-01-31T23:59:59Z"]
+    }
+  ]
+}

extensions/dimensions/schema.json

@@ -0,0 +1,36 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "type": "object",
+  "title": "STAC Dimensions Extension Spec",
+  "properties": {
+    "dim:dimensions": {
+      "type": "array",
+      "title": "Dimensions",
+      "items": {
+        "type": "object",
+        "required": [
+          "label"
+        ],
+        "properties": {
+          "label": {
+            "type": "string",
+            "title": "Label"
+          },
+          "unit": {
+            "type": "string",
+            "title": "Unit of Measurement"
+          },
+          "extent": {
+            "type": "array",
+            "title": "Data Extent",
+            "minItems": 2,
+            "maxItems": 2,
+            "items": {
+              "type": ["number", "string"]
+            }
+          }
+        }
+      }
+    }
+  }
+}