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<p style="text-align: left;">In the <a class="reference internal" href="/courses/course-v1:digitalearthafrica+DEA101+2021/jump_to_id/fda78c400c624dcb9eecfa55fba8fd07" style="box-sizing: border-box; color: #2980b9; text-decoration-line: none; cursor: pointer;" target="[object Object]">previous section</a>, we loaded the Landsat 8 dataset onto the <a class="reference external" href="https://maps.digitalearth.africa/" target="_blank">Digital Earth Africa Map</a> and saw it only covers certain parts of Africa each day. The section on Digital Earth Africa products tells us Landsat 8 data is only available at certain times in some countries.</p>
<p style="text-align: left;">How do we know specifically <strong>where </strong>and <strong>when</strong> data is available? Before we start any analysis, we can answer this question by verifying existing data on the <a class="reference external" href="https://explorer.digitalearth.africa/" target="_blank">Digital Earth Africa Metadata Explorer</a>. The Metadata Explorer can be found at <a class="reference external" href="https://explorer.digitalearth.africa/" target="_blank">https://explorer.digitalearth.africa/</a>.</p>
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<p style="text-align: left;">In this section, we will use the <a class="reference external" href="https://explorer.digitalearth.africa/" target="_blank">Digital Earth Africa Metadata Explorer</a> to check where data is available for a selected time period. The place we will investigate is Tanzania, for the time period of 2018.</p>
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<p style="text-align: left;">The <a class="reference external" href="https://explorer.digitalearth.africa/" target="_blank" style="box-sizing: border-box; color: #2980b9; text-decoration-line: none; cursor: pointer;">Digital Earth Africa Metadata Explorer</a> and <a class="reference external" href="https://maps.digitalearth.africa/" target="_blank" style="box-sizing: border-box; color: #2980b9; text-decoration-line: none; cursor: pointer;">Digital Earth Africa Map</a> look similar, but they are designed for different purposes.</p>
<p style="text-align: left;">Use the <strong><a class="reference external" href="https://maps.digitalearth.africa/" target="_blank" style="box-sizing: border-box; color: #2980b9; text-decoration-line: none; cursor: pointer;">Digital Earth Africa Map</a></strong> if you:</p>
<ul style="text-align: left;">
<ul>
<li>Want to see what the product or dataset looks like</li>
</ul>
</ul>
<p style="text-align: left;">Use the <strong><a class="reference external" href="https://explorer.digitalearth.africa/" target="_blank" style="box-sizing: border-box; color: #2980b9; text-decoration-line: none; cursor: pointer;">Digital Earth Africa Metadata Explorer</a></strong> if you:</p>
<ul>
<ul>
<li style="text-align: left;">Want to know exactly where and when you can find data</li>
</ul>
</ul>
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<p style="text-align: left;"><span style="color: #3c3c3c;">Open </span><a class="reference external" href="https://explorer.digitalearth.africa/" target="_blank" style="box-sizing: border-box; color: #2980b9; text-decoration-line: none; cursor: pointer;">https://explorer.digitalearth.africa/</a><span style="color: #3c3c3c;">. This will display the Metadata Explorer user interface.</span></p>
<p style="text-align: left;"><span style="color: #3c3c3c;"><img width="80%" src="https://learn.digitalearthafrica.org/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block@explorer_ui1.png" alt="explorer user interface" /></span></p>
<p style="text-align: left;">The Digital Earth Africa Metadata Explorer has four main sections.</p>
<ul style="text-align: left;">
<li style="box-sizing: border-box; list-style: decimal; margin-left: 24px;"><strong style="box-sizing: border-box;">Product selection:</strong> This shows the currently-selected product. Click the selected product name to open the products dropdown menu.</li>
<li style="box-sizing: border-box; list-style: decimal; margin-left: 24px;"><strong style="box-sizing: border-box;">Time period:</strong> This shows the time period for which the selected product is being displayed. Click the selected time period to open the time selection dropdown menu.</li>
<li style="box-sizing: border-box; list-style: decimal; margin-left: 24px;"><strong style="box-sizing: border-box;">Map display:</strong> This shows where data is available, for the selected time and product. Blue shaded tiles indicate the presence of data.</li>
<li style="box-sizing: border-box; list-style: decimal; margin-left: 24px;"><strong style="box-sizing: border-box;">Product information:</strong> The sidebar shows more information about the data for the selected time and product. For example, this includes how many datasets are selected, the name of the datasets in the product, and its coordinate reference system.</li>
</ul>
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<h3>Select the Landsat 8 product</h3>
<ol>
<li style="text-align: left;">
<p><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">Click the <strong style="box-sizing: border-box;">product selection</strong> bar to open the dropdown menu. Select <strong style="box-sizing: border-box;">ls8_sr</strong>. This selects the Landsat 8 product.</span></p>
</li>
</ol>
<p style="box-sizing: border-box; line-height: 24px; margin: 0px 0px 24px; font-size: 16px;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;"><img alt="Metadata Explorer Landsat 8." class="no-scaled-link" src="https://learn.digitalearthafrica.org/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block@explorer_ls8.png" style="box-sizing: border-box; border: 0px; vertical-align: middle; width: 600px;" /></span></p>
<ol class="arabic simple" start="2">
<li style="box-sizing: border-box; list-style: decimal; margin-left: 24px;">
<p style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">Click the <strong style="box-sizing: border-box;">time</strong> bar to open the dropdown menu. Select <strong style="box-sizing: border-box;">2018</strong>. This will show all Landsat 8 datasets for 2018.</span></p>
</li>
</ol>
<p style="box-sizing: border-box; line-height: 24px; margin: 0px 0px 24px; font-size: 16px;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;"><img alt="Metadata Explorer Landsat 8 2018." class="no-scaled-link" src="https://learn.digitalearthafrica.org/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block@explorer_2018.png" style="box-sizing: border-box; border: 0px; vertical-align: middle; width: 600px;" /></span></p>
<ol class="arabic simple" start="3">
<li style="box-sizing: border-box; list-style: decimal; margin-left: 24px;">
<p style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">Click the <strong style="box-sizing: border-box;">all months</strong> bar to open the dropdown menu. Select <strong style="box-sizing: border-box;">August</strong>. This will show all the Landsat 8 datasets for August 2018.</span></p>
</li>
</ol>
<p style="box-sizing: border-box; line-height: 24px; margin: 0px 0px 24px; font-size: 16px;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;"><img alt="Metadata Explorer Landsat 8 2018." class="no-scaled-link" src="https://learn.digitalearthafrica.org/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block@explorer_august.png" style="box-sizing: border-box; border: 0px; vertical-align: middle; width: 600px;" /></span></p>
<ol class="arabic simple" start="4">
<li style="box-sizing: border-box; list-style: decimal; margin-left: 24px;">
<p style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">Click the <strong style="box-sizing: border-box;">all days</strong> bar to open the dropdown menu. Select <strong style="box-sizing: border-box;">11th</strong>, This will show all the Landsat 8 datasets for 11 August 2018.</span></p>
</li>
</ol>
<p style="box-sizing: border-box; line-height: 24px; margin: 0px 0px 24px; font-size: 16px;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;"><img alt="Metadata Explorer Landsat 8 2018." class="no-scaled-link" src="https://learn.digitalearthafrica.org/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block@explorer_11august2018.png" style="box-sizing: border-box; border: 0px; vertical-align: middle; width: 600px;" /></span></p>
<ol class="arabic simple" start="5">
<li style="text-align: left; box-sizing: border-box; list-style: decimal; margin-left: 24px;">
<p style="box-sizing: border-box; line-height: 24px; margin: 0px; font-size: 16px;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">The <strong style="box-sizing: border-box;">map display</strong> will now show all the Landsat 8 datasets for 11 August 2018 as blue shaded boxes. Use the <strong style="box-sizing: border-box;">+</strong> button on the map to zoom in, and click and drag to pan the map.</span></p>
</li>
</ol>
<p style="box-sizing: border-box; line-height: 24px; margin: 0px 0px 24px; font-size: 16px;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;"><img alt="Metadata Explorer Landsat 8 2018." class="no-scaled-link" src="https://learn.digitalearthafrica.org/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block@explorer_zoom.png" style="box-sizing: border-box; border: 0px; vertical-align: middle; width: 600px;" /></span></p>
<p style="box-sizing: border-box; line-height: 24px; margin: 0px 0px 24px; font-size: 16px; text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">We can see that there is only data available for some African countries. Let’s take a closer look at Tanzania.</span></p>
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<h3 style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">Zoom in on Tanzania</span></h3>
<p style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">Use the map’s <strong style="box-sizing: border-box;">+</strong> button to zoom in on Africa. Click and drag to see Tanzania.</span></p>
<p style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;"><img alt="Metadata Explorer Landsat 8 2018." class="no-scaled-link" src="https://learn.digitalearthafrica.org/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block@explorer_tanzania.png" style="box-sizing: border-box; border: 0px; vertical-align: middle; width: 600px;" /></span></p>
<p style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">We can see the data for 11 August 2018 (blue shaded boxes) covers certain parts of Tanzania, which means areas within Tanzania are a suitable location to choose for data analysis for that day. </span></p>
<p style="text-align: left;"><span style="font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;">For example, for that day (11 August 2018) we would not be able to do any Landsat 8 analysis over the city of Dodoma in Tanzania, as it does not have any data available for that time.</span></p>
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<p style="text-align: left;">You now know how to use the Digital Earth Africa Metadata Explorer to check where and when you can perform data analysis. The next step is loading the data.</p>
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<div class="page-banner"><div class="alert alert-warning"><span class="icon icon-alert fa fa fa-warning" aria-hidden="true"></span><div class="message-content">Knowledge Check: Data availability is only accessible to enrolled learners. Sign in or register, and enroll in this course to view it.</div></div></div>
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