Draft point cloud STAC extension

extensions/README.md

@@ -53,6 +53,7 @@ stable for over a year and are used in twenty or more implementations.
 | [Single Item](single-item/README.md) (`item`)                | Item             | Provides a way to specify several fields in individual Items that usually reside on the collection-level such as license and providers. | *Proposal* |
 | [Scientific](scientific//README.md) (`sci`)                  | Item             | Scientific metadata is considered to be data that indicate from which publication a collection originates and how the collection itself should be cited or referenced. | *Proposal* |
 | [Transaction](transaction//README.md)                        | API              | Provides an API extension to support the creation, editing, and deleting of items on a specific WFS3 collection. | *Pilot* |
+| [Point Cloud](pointcloud/README.md) (`pc`)             	| Item	| Provides a way to describe point cloud datasets. The point clouds can come from either active or passive sensors, and data is frequently acquired using tools such as LiDAR or coincidence-matched imagery. | *Proposal* |
 
 ## Third-party / vendor extensions
 

extensions/pointcloud/README.md

@@ -0,0 +1,54 @@
+# Point Cloud Extension Specification (`pc`)
+
+**Extension [Maturity Classification](../README.md#extension-maturity): Proposal**
+
+This document explains the fields of the Point Cloud Extension to a STAC Item,
+which allows STAC to more fully describe point cloud datasets. The point clouds can
+come from either active or passive sensors, and data is frequently acquired using
+tools such as LiDAR or coincidence-matched imagery.
+
+- [Example](example-autzen.json)
+- JSON Schema is missing. PRs are welcome.
+
+## Item Fields
+
+| Field Name    | Type                | Description |
+| ------------- | ------------------- | ----------- |
+| pc:count      | integer             | **REQUIRED.** The number of points in the item. |
+| pc:type       | string              | **REQUIRED.** Phenomenology type for the point cloud. Possible valid values might include `lidar`, `eopc`, `radar`, `sonar`, or `other` |
+| pc:encoding   | string              | **REQUIRED.** Content encoding or format of the data. |
+| pc:schema     | [Schema Object]     | **REQUIRED.** A sequential array of items that define the dimensions and their types. |
+| pc:density    | number              | Number of points per square unit area. |
+| pc:schema     | [Schema Object]     | A sequential array of items that define the dimensions and their types. |
+| pc:statistics | [Statistics Object] | A sequential array of items mapping to `pc:schema` defines per-channel statistics. |
+
+### Schema Object
+
+A sequential array of items that define the dimensions or channels of
+the point cloud, their types, and their sizes (in full bytes).
+
+| Field Name | Type    | Description |
+| ---------- | ------- | -------------------------- |
+| name       | string  | **REQUIRED.** The name of the dimension. |
+| size       | integer | **REQUIRED.** The size of the dimension in bytes. Whole bytes only are supported.|
+| type       | string  | **REQUIRED.** Dimension type. Valid values include `floating`, `unsigned`, and `signed`|
+
+### Statistics Object
+
+A sequential array of items mapping to `pc:schema` defines per-channel statistics. All fields
+are optional.
+
+| Field Name | Type    | Description |
+| ---------- | ------- | ----------- |
+| average    | number  | The average of the channel. |
+| count      | integer | The number of elements in the channel. |
+| maximum    | number  | The maximum value of the channel. |
+| minimum    | number  | The minimum value of the channel. |
+| name       | string  | The name of the channel. |
+| position   | integer | Position of the channel in the schema.|
+| stddev     | number  | The standard deviation of the channel. |
+| variance   | number  | The variance of the channel. |
+
+## Implementations
+
+None yet, still in proposal stage.

extensions/pointcloud/example-autzen.json

@@ -0,0 +1,300 @@
+{
+  "assets": {},
+  "bbox": [
+    -123.0755422,
+    44.04971882,
+    123.791472,
+    -123.0619599,
+    44.06278031,
+    187.531248
+  ],
+  "geometry": {
+    "coordinates": [
+      [
+        [
+          -123.07498674,
+          44.04971882
+        ],
+        [
+          -123.07554223,
+          44.06248623
+        ],
+        [
+          -123.0625126,
+          44.06278031
+        ],
+        [
+          -123.06195992,
+          44.05001283
+        ],
+        [
+          -123.07498674,
+          44.04971882
+        ]
+      ]
+    ],
+    "type": "Polygon"
+  },
+  "id": "autzen-full.laz",
+  "links": [
+    {
+      "href": "/Users/hobu/dev/git/pdal/test/data/autzen/autzen-full.laz",
+      "rel": "self"
+    }
+  ],
+  "properties": {
+    "datetime": "2013-07-17T00:00:00-05:00Z",
+    "item:license": "LICENSE",
+    "item:provider": "USGS",
+    "pc:count": 10653336,
+    "pc:density": 0,
+    "pc:encoding": "LASzip",
+    "pc:schema": [
+      {
+        "name": "X",
+        "size": 8,
+        "type": "floating"
+      },
+      {
+        "name": "Y",
+        "size": 8,
+        "type": "floating"
+      },
+      {
+        "name": "Z",
+        "size": 8,
+        "type": "floating"
+      },
+      {
+        "name": "Intensity",
+        "size": 2,
+        "type": "unsigned"
+      },
+      {
+        "name": "ReturnNumber",
+        "size": 1,
+        "type": "unsigned"
+      },
+      {
+        "name": "NumberOfReturns",
+        "size": 1,
+        "type": "unsigned"
+      },
+      {
+        "name": "ScanDirectionFlag",
+        "size": 1,
+        "type": "unsigned"
+      },
+      {
+        "name": "EdgeOfFlightLine",
+        "size": 1,
+        "type": "unsigned"
+      },
+      {
+        "name": "Classification",
+        "size": 1,
+        "type": "unsigned"
+      },
+      {
+        "name": "ScanAngleRank",
+        "size": 4,
+        "type": "floating"
+      },
+      {
+        "name": "UserData",
+        "size": 1,
+        "type": "unsigned"
+      },
+      {
+        "name": "PointSourceId",
+        "size": 2,
+        "type": "unsigned"
+      },
+      {
+        "name": "GpsTime",
+        "size": 8,
+        "type": "floating"
+      },
+      {
+        "name": "Red",
+        "size": 2,
+        "type": "unsigned"
+      },
+      {
+        "name": "Green",
+        "size": 2,
+        "type": "unsigned"
+      },
+      {
+        "name": "Blue",
+        "size": 2,
+        "type": "unsigned"
+      }
+    ],
+    "pc:statistics": [
+      {
+        "average": 637294.1783,
+        "count": 10653336,
+        "maximum": 639003.73,
+        "minimum": 635577.79,
+        "name": "X",
+        "position": 0,
+        "stddev": 967.9329805,
+        "variance": 936894.2548
+      },
+      {
+        "average": 851247.6953,
+        "count": 10653336,
+        "maximum": 853537.66,
+        "minimum": 848882.15,
+        "name": "Y",
+        "position": 1,
+        "stddev": 1322.356387,
+        "variance": 1748626.415
+      },
+      {
+        "average": 434.1025002,
+        "count": 10653336,
+        "maximum": 615.26,
+        "minimum": 406.14,
+        "name": "Z",
+        "position": 2,
+        "stddev": 24.67893148,
+        "variance": 609.0496589
+      },
+      {
+        "average": 77.14742312,
+        "count": 10653336,
+        "maximum": 254,
+        "minimum": 0,
+        "name": "Intensity",
+        "position": 3,
+        "stddev": 62.62422344,
+        "variance": 3921.793362
+      },
+      {
+        "average": 1.17801438,
+        "count": 10653336,
+        "maximum": 4,
+        "minimum": 1,
+        "name": "ReturnNumber",
+        "position": 4,
+        "stddev": 0.4653418642,
+        "variance": 0.2165430505
+      },
+      {
+        "average": 1.358579791,
+        "count": 10653336,
+        "maximum": 4,
+        "minimum": 1,
+        "name": "NumberOfReturns",
+        "position": 5,
+        "stddev": 0.6656066447,
+        "variance": 0.4430322055
+      },
+      {
+        "average": 0.4989654884,
+        "count": 10653336,
+        "maximum": 1,
+        "minimum": 0,
+        "name": "ScanDirectionFlag",
+        "position": 6,
+        "stddev": 0.4999993213,
+        "variance": 0.2499993213
+      },
+      {
+        "average": 0,
+        "count": 10653336,
+        "maximum": 0,
+        "minimum": 0,
+        "name": "EdgeOfFlightLine",
+        "position": 7,
+        "stddev": 0,
+        "variance": 0
+      },
+      {
+        "average": 1.256686262,
+        "count": 10653336,
+        "maximum": 2,
+        "minimum": 1,
+        "name": "Classification",
+        "position": 8,
+        "stddev": 0.436805292,
+        "variance": 0.1907988632
+      },
+      {
+        "average": -0.812061405,
+        "count": 10653336,
+        "maximum": 20,
+        "minimum": -21,
+        "name": "ScanAngleRank",
+        "position": 9,
+        "stddev": 8.484319324,
+        "variance": 71.98367439
+      },
+      {
+        "average": 126.4052859,
+        "count": 10653336,
+        "maximum": 156,
+        "minimum": 115,
+        "name": "UserData",
+        "position": 10,
+        "stddev": 3.833000243,
+        "variance": 14.69189086
+      },
+      {
+        "average": 7329.903705,
+        "count": 10653336,
+        "maximum": 7334,
+        "minimum": 7326,
+        "name": "PointSourceId",
+        "position": 11,
+        "stddev": 3.107430355,
+        "variance": 9.656123408
+      },
+      {
+        "average": 121.3214254,
+        "count": 10653336,
+        "maximum": 255,
+        "minimum": 35,
+        "name": "Red",
+        "position": 12,
+        "stddev": 45.56263834,
+        "variance": 2075.954013
+      },
+      {
+        "average": 126.2526972,
+        "count": 10653336,
+        "maximum": 255,
+        "minimum": 49,
+        "name": "Green",
+        "position": 13,
+        "stddev": 36.85451838,
+        "variance": 1358.255525
+      },
+      {
+        "average": 111.2207554,
+        "count": 10653336,
+        "maximum": 255,
+        "minimum": 49,
+        "name": "Blue",
+        "position": 14,
+        "stddev": 31.95561927,
+        "variance": 1021.161603
+      },
+      {
+        "average": 247608.4011,
+        "count": 10653336,
+        "maximum": 249783.703,
+        "minimum": 245369.8966,
+        "name": "GpsTime",
+        "position": 15,
+        "stddev": 1178.538827,
+        "variance": 1388953.768
+      }
+    ],
+    "pc:type": "lidar",
+    "title": "USGS 3DEP LiDAR"
+  },
+  "type": "Feature"
+}