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<h1 id="Create-a-STAC-Item-that-Implements-the-EO-Extension-Using-PySTAC">Create a STAC Item that Implements the EO Extension Using PySTAC<a class="anchor-link" href="#Create-a-STAC-Item-that-Implements-the-EO-Extension-Using-PySTAC">¶</a></h1>
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<p>In the <a href="/en/tutorials/2-create-stac-catalog-python/index.html">previous tutorial</a>, you created a STAC Item and added it to a STAC Catalog. The item you created only implemented the core STAC Item specification. With <a href="https://github.com/radiantearth/stac-spec/tree/v0.9.0/extensions">extensions</a>, we can record more information and add additional functionality to the item.</p>
<p>This tutorial builds off of the knowledge from the previous tutorial. Let's create an item that utilizes a common STAC Extension: the <a href="https://github.com/radiantearth/stac-spec/tree/v0.8.1/extensions/eo">Electro-Optical (EO) Extension</a>.</p>
<p>We will continue to use the data from the previous tutorial and will add the item we create into the STAC Catalog you just created.</p>
<p>Given that we know the tiff image we are working with is a <a href="https://worldview3.digitalglobe.com/">WorldView-3</a> image that has earth observation data, we can enable the <a href="https://github.com/radiantearth/stac-spec/tree/v0.8.1/extensions/eo">EO Extension</a> to add band information.</p>
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<h2 id="Dependencies">Dependencies<a class="anchor-link" href="#Dependencies">¶</a></h2><p>If you need to install pystac, rasterio, or pystac, uncomment the lines below and run the cell.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="c1"># ! pip install pystac</span>
<span class="c1"># ! pip install asterio</span>
<span class="c1"># ! pip install shapely</span>
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<h2 id="Import-Packages-and-Store-Data">Import Packages and Store Data<a class="anchor-link" href="#Import-Packages-and-Store-Data">¶</a></h2><p>To begin, import the packages and classes that you need to access data and work with STAC Items in Python.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="kn">import</span> <span class="nn">os</span>
<span class="kn">import</span> <span class="nn">rasterio</span>
<span class="kn">import</span> <span class="nn">urllib.request</span>
<span class="kn">import</span> <span class="nn">pystac</span>
<span class="kn">from</span> <span class="nn">shapely.geometry</span> <span class="kn">import</span> <span class="n">Polygon</span><span class="p">,</span> <span class="n">mapping</span>
<span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">datetime</span><span class="p">,</span> <span class="n">timezone</span>
<span class="kn">from</span> <span class="nn">pystac.extensions.eo</span> <span class="kn">import</span> <span class="n">Band</span><span class="p">,</span> <span class="n">EOExtension</span>
<span class="kn">from</span> <span class="nn">tempfile</span> <span class="kn">import</span> <span class="n">TemporaryDirectory</span>
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<p>Just like in the previous tutorial, we will set up a temporary directory and store the same image in it.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="c1"># Set the temporary directory to store source data</span>
<span class="n">tmp_dir</span> <span class="o">=</span> <span class="n">TemporaryDirectory</span><span class="p">()</span>
<span class="n">img_path</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">tmp_dir</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="s1">'image.tif'</span><span class="p">)</span>
<span class="c1"># Fetch and store data</span>
<span class="n">url</span> <span class="o">=</span> <span class="p">(</span><span class="s1">'https://spacenet-dataset.s3.amazonaws.com/'</span>
<span class="s1">'spacenet/SN5_roads/train/AOI_7_Moscow/MS/'</span>
<span class="s1">'SN5_roads_train_AOI_7_Moscow_MS_chip996.tif'</span><span class="p">)</span>
<span class="n">urllib</span><span class="o">.</span><span class="n">request</span><span class="o">.</span><span class="n">urlretrieve</span><span class="p">(</span><span class="n">url</span><span class="p">,</span> <span class="n">img_path</span><span class="p">)</span>
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<pre>('/var/folders/73/z5lbqv_s6l7fcfx464_pn8p80000gn/T/tmpoxerm5i9/image.tif',
<http.client.HTTPMessage at 0x12757a740>)</pre>
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<h2 id="Define-the-Bands-of-WorldView-3">Define the Bands of WorldView-3<a class="anchor-link" href="#Define-the-Bands-of-WorldView-3">¶</a></h2><p>To add the EO information to an item we'll need to specify some more data. First, let's define the bands of WorldView-3. We have collected this band information from the <a href="https://www.spaceimagingme.com/downloads/sensors/datasheets/DG_WorldView3_DS_2014.pdf">WorldView-3 Data Sheet</a>.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">wv3_bands</span> <span class="o">=</span> <span class="p">[</span><span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Coastal'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Coastal: 400 - 450 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'coastal'</span><span class="p">),</span>
<span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Blue'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Blue: 450 - 510 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'blue'</span><span class="p">),</span>
<span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Green'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Green: 510 - 580 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'green'</span><span class="p">),</span>
<span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Yellow'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Yellow: 585 - 625 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'yellow'</span><span class="p">),</span>
<span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Red'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Red: 630 - 690 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'red'</span><span class="p">),</span>
<span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Red Edge'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Red Edge: 705 - 745 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'rededge'</span><span class="p">),</span>
<span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Near-IR1'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Near-IR1: 770 - 895 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'nir08'</span><span class="p">),</span>
<span class="n">Band</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Near-IR2'</span><span class="p">,</span> <span class="n">description</span><span class="o">=</span><span class="s1">'Near-IR2: 860 - 1040 nm'</span><span class="p">,</span> <span class="n">common_name</span><span class="o">=</span><span class="s1">'nir09'</span><span class="p">)]</span>
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<p>Notice that we used the <code>.create</code> method to create new band information.</p>
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<h2 id="Collect-the-Item's-geometry-and-bbox">Collect the Item's <code>geometry</code> and <code>bbox</code><a class="anchor-link" href="#Collect-the-Item's-geometry-and-bbox">¶</a></h2><p>To get the bounding box and footprint of the image, we will utilize the <code>get_bbox_and_footprint</code> function we first used in the <a href="/en/tutorials/2-create-stac-catalog-python/index.html">Create a STAC Catalog Tutorial</a>.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">def</span> <span class="nf">get_bbox_and_footprint</span><span class="p">(</span><span class="n">raster</span><span class="p">):</span>
<span class="k">with</span> <span class="n">rasterio</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="n">raster</span><span class="p">)</span> <span class="k">as</span> <span class="n">r</span><span class="p">:</span>
<span class="n">bounds</span> <span class="o">=</span> <span class="n">r</span><span class="o">.</span><span class="n">bounds</span>
<span class="n">bbox</span> <span class="o">=</span> <span class="p">[</span><span class="n">bounds</span><span class="o">.</span><span class="n">left</span><span class="p">,</span> <span class="n">bounds</span><span class="o">.</span><span class="n">bottom</span><span class="p">,</span> <span class="n">bounds</span><span class="o">.</span><span class="n">right</span><span class="p">,</span> <span class="n">bounds</span><span class="o">.</span><span class="n">top</span><span class="p">]</span>
<span class="n">footprint</span> <span class="o">=</span> <span class="n">Polygon</span><span class="p">([</span>
<span class="p">[</span><span class="n">bounds</span><span class="o">.</span><span class="n">left</span><span class="p">,</span> <span class="n">bounds</span><span class="o">.</span><span class="n">bottom</span><span class="p">],</span>
<span class="p">[</span><span class="n">bounds</span><span class="o">.</span><span class="n">left</span><span class="p">,</span> <span class="n">bounds</span><span class="o">.</span><span class="n">top</span><span class="p">],</span>
<span class="p">[</span><span class="n">bounds</span><span class="o">.</span><span class="n">right</span><span class="p">,</span> <span class="n">bounds</span><span class="o">.</span><span class="n">top</span><span class="p">],</span>
<span class="p">[</span><span class="n">bounds</span><span class="o">.</span><span class="n">right</span><span class="p">,</span> <span class="n">bounds</span><span class="o">.</span><span class="n">bottom</span><span class="p">]</span>
<span class="p">])</span>
<span class="k">return</span> <span class="p">(</span><span class="n">bbox</span><span class="p">,</span> <span class="n">mapping</span><span class="p">(</span><span class="n">footprint</span><span class="p">))</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">bbox</span><span class="p">,</span> <span class="n">footprint</span> <span class="o">=</span> <span class="n">get_bbox_and_footprint</span><span class="p">(</span><span class="n">img_path</span><span class="p">)</span>
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<p>We can now create an item, enable the EO Extension, add the band information and add it to our catalog:</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">eo_item</span> <span class="o">=</span> <span class="n">pystac</span><span class="o">.</span><span class="n">Item</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="s1">'local-image-eo'</span><span class="p">,</span>
<span class="n">geometry</span><span class="o">=</span><span class="n">footprint</span><span class="p">,</span>
<span class="n">bbox</span><span class="o">=</span><span class="n">bbox</span><span class="p">,</span>
<span class="n">datetime</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">(),</span>
<span class="n">properties</span><span class="o">=</span><span class="p">{})</span>
<span class="n">eo</span> <span class="o">=</span> <span class="n">EOExtension</span><span class="o">.</span><span class="n">ext</span><span class="p">(</span><span class="n">eo_item</span><span class="p">,</span> <span class="n">add_if_missing</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
<span class="n">eo</span><span class="o">.</span><span class="n">apply</span><span class="p">(</span><span class="n">bands</span><span class="o">=</span><span class="n">wv3_bands</span><span class="p">)</span>
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<p>There are also <a href="https://github.com/radiantearth/stac-spec/blob/v0.9.0/item-spec/common-metadata.md">common metadata</a> fields that we can use to capture additional information about the WorldView-3 imagery:</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">eo_item</span><span class="o">.</span><span class="n">common_metadata</span><span class="o">.</span><span class="n">platform</span> <span class="o">=</span> <span class="s2">"Maxar"</span>
<span class="n">eo_item</span><span class="o">.</span><span class="n">common_metadata</span><span class="o">.</span><span class="n">instruments</span> <span class="o">=</span> <span class="p">[</span><span class="s2">"WorldView3"</span><span class="p">]</span>
<span class="n">eo_item</span><span class="o">.</span><span class="n">common_metadata</span><span class="o">.</span><span class="n">gsd</span> <span class="o">=</span> <span class="mf">0.3</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="nb">print</span><span class="p">(</span><span class="n">eo_item</span><span class="p">)</span>
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<pre><Item id=local-image-eo>
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<p>We can use the EO Extension to add bands to the assets we add to the item:</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">asset</span> <span class="o">=</span> <span class="n">pystac</span><span class="o">.</span><span class="n">Asset</span><span class="p">(</span><span class="n">href</span><span class="o">=</span><span class="n">img_path</span><span class="p">,</span>
<span class="n">media_type</span><span class="o">=</span><span class="n">pystac</span><span class="o">.</span><span class="n">MediaType</span><span class="o">.</span><span class="n">GEOTIFF</span><span class="p">)</span>
<span class="n">eo_item</span><span class="o">.</span><span class="n">add_asset</span><span class="p">(</span><span class="s2">"image"</span><span class="p">,</span> <span class="n">asset</span><span class="p">)</span>
<span class="n">eo_on_asset</span> <span class="o">=</span> <span class="n">EOExtension</span><span class="o">.</span><span class="n">ext</span><span class="p">(</span><span class="n">eo_item</span><span class="o">.</span><span class="n">assets</span><span class="p">[</span><span class="s2">"image"</span><span class="p">])</span>
<span class="n">eo_on_asset</span><span class="o">.</span><span class="n">apply</span><span class="p">(</span><span class="n">wv3_bands</span><span class="p">)</span>
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<p>If we look at the asset's JSON representation, we can see the appropriate band indexes are set:</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">asset</span><span class="o">.</span><span class="n">to_dict</span><span class="p">()</span>
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<pre>{'href': '/var/folders/73/z5lbqv_s6l7fcfx464_pn8p80000gn/T/tmpoxerm5i9/image.tif',
'type': <MediaType.GEOTIFF: 'image/tiff; application=geotiff'>,
'eo:bands': [{'name': 'Coastal',
'common_name': 'coastal',
'description': 'Coastal: 400 - 450 nm'},
{'name': 'Blue', 'common_name': 'blue', 'description': 'Blue: 450 - 510 nm'},
{'name': 'Green',
'common_name': 'green',
'description': 'Green: 510 - 580 nm'},
{'name': 'Yellow',
'common_name': 'yellow',
'description': 'Yellow: 585 - 625 nm'},
{'name': 'Red', 'common_name': 'red', 'description': 'Red: 630 - 690 nm'},
{'name': 'Red Edge',
'common_name': 'rededge',
'description': 'Red Edge: 705 - 745 nm'},
{'name': 'Near-IR1',
'common_name': 'nir08',
'description': 'Near-IR1: 770 - 895 nm'},
{'name': 'Near-IR2',
'common_name': 'nir09',
'description': 'Near-IR2: 860 - 1040 nm'}]}</pre>
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<p>Let's create a catalog, add the item that uses the EO Extension, and save to a new STAC.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">catalog</span> <span class="o">=</span> <span class="n">pystac</span><span class="o">.</span><span class="n">Catalog</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="s1">'tutorial-catalog'</span><span class="p">,</span>
<span class="n">description</span><span class="o">=</span><span class="s1">'This Catalog is a basic demonstration Catalog to teach the use of the eo extension.'</span><span class="p">)</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">catalog</span><span class="o">.</span><span class="n">add_item</span><span class="p">(</span><span class="n">eo_item</span><span class="p">)</span>
<span class="nb">list</span><span class="p">(</span><span class="n">catalog</span><span class="o">.</span><span class="n">get_items</span><span class="p">())</span>
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<pre>[<Item id=local-image-eo>]</pre>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">catalog</span><span class="o">.</span><span class="n">normalize_and_save</span><span class="p">(</span><span class="n">root_href</span><span class="o">=</span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">tmp_dir</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="s1">'stac-eo'</span><span class="p">),</span>
<span class="n">catalog_type</span><span class="o">=</span><span class="n">pystac</span><span class="o">.</span><span class="n">CatalogType</span><span class="o">.</span><span class="n">SELF_CONTAINED</span><span class="p">)</span>
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<p>Now, if we read the catalog from the filesystem, PySTAC recognizes that the item implements eo and to use its functionality, e.g. getting the bands off the asset:</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">catalog2</span> <span class="o">=</span> <span class="n">pystac</span><span class="o">.</span><span class="n">read_file</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">tmp_dir</span><span class="o">.</span><span class="n">name</span><span class="p">,</span> <span class="s1">'stac-eo'</span><span class="p">,</span> <span class="s1">'catalog.json'</span><span class="p">))</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">assert</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">catalog2</span><span class="p">,</span> <span class="n">pystac</span><span class="o">.</span><span class="n">Catalog</span><span class="p">)</span>
<span class="nb">list</span><span class="p">(</span><span class="n">catalog2</span><span class="o">.</span><span class="n">get_items</span><span class="p">())</span>
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<pre>[<Item id=local-image-eo>]</pre>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">item</span><span class="p">:</span> <span class="n">pystac</span><span class="o">.</span><span class="n">Item</span> <span class="o">=</span> <span class="nb">next</span><span class="p">(</span><span class="n">catalog2</span><span class="o">.</span><span class="n">get_all_items</span><span class="p">())</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="k">assert</span> <span class="n">EOExtension</span><span class="o">.</span><span class="n">has_extension</span><span class="p">(</span><span class="n">item</span><span class="p">)</span>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">eo_on_asset</span> <span class="o">=</span> <span class="n">EOExtension</span><span class="o">.</span><span class="n">ext</span><span class="p">(</span><span class="n">item</span><span class="o">.</span><span class="n">assets</span><span class="p">[</span><span class="s2">"image"</span><span class="p">])</span>
<span class="nb">print</span><span class="p">(</span><span class="n">eo_on_asset</span><span class="o">.</span><span class="n">bands</span><span class="p">)</span>
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<pre>[<Band name=Coastal>, <Band name=Blue>, <Band name=Green>, <Band name=Yellow>, <Band name=Red>, <Band name=Red Edge>, <Band name=Near-IR1>, <Band name=Near-IR2>]
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<h2 id="Cleanup">Cleanup<a class="anchor-link" href="#Cleanup">¶</a></h2><p>Don't forget to clean up the temporary directory.</p>
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<div class=" highlight hl-ipython3"><pre><span></span><span class="n">tmp_dir</span><span class="o">.</span><span class="n">cleanup</span><span class="p">()</span>
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<p>Now you have created an Item with a STAC Extension. In the <a href="/en/tutorials/4-create-stac-collection/index.html">following tutorial</a>, you will learn how to add a Collection to this STAC Catalog.</p>
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<h4 id="Join-the-conversation">Join the conversation<a class="anchor-link" href="#Join-the-conversation">¶</a></h4><p>If you have any questions, you’re welcome to ask our community on <a href="https://app.gitter.im/#/room/#SpatioTemporal-Asset-Catalog_Lobby">Gitter</a>.</p>
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