Tacloban City, 1944 vs. 2013

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<div id='map'></div>
<div id='zoomlens' class='overlay'>
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          <a class="brand">Tacloban, Philippines | 1944 vs. 2013</a>
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        <p>This map compares a section of Tacloban City mapped in 1944 with Openstreetmap data from the present day. Drag the slider on the left to toggle between old and new.</p>
        <hr>
        <ul>
          <li>1944 Map by U.S. Army Map Service, provided by University of Texas <a href="https://www.lib.utexas.edu/maps/ams/philippines_city_plans/txu-pclmaps-oclc-6610188-tacloban.jpg" target="_blank">PCL Map Collection</a></li>
          <li>2012 Imagery provided by <a href="https://www.mapbox.com/about/maps/" target="_blank">Mapbox</a></li>
          <li>Street and Reference data by <a href="https://osm.org" target="_blank">OpenStreetmap Contributors</a></li>
          <li>Application by <a href="https://geosprocket.com" target="_blank">Geosprocket</a></li>
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var oldLayer = L.tileLayer('https://mapwarper.net/maps/tile/2110/{z}/{x}/{y}.png').addTo(zoommap);

map.setView([11.2440, 125.0027], 16);

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map.on('mousemove', update);
map.on('zoomend', zoom);

function zoom(e) {
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function update(e) {
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