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Object Type description, Fictional case example, radius explaination
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@SteffenME
SteffenME authored Jan 4, 2024
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Expand Up @@ -5,6 +5,68 @@ <h3>Background</h3>
<p>
This software acts as a web user interface for the <a href="https://opendrift.github.io/gallery/example_leeway.html">OpenDrift Leeway</a> model. The basis for the simulation are experiments performed by the US Coast Guard in 1999. The results are published on <a href="https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA366414.xhtml">https://ntrl.ntis.gov</a>, which include desriptions of the objects that were tested (2-13 and following pages).
</p>
<h3>Object Types</h3>
<p>
The default object type for simulatoins is a life raft (ID: 27). Some alternatives are:
</p>
<style type="text/css">
.tg {border-collapse:collapse;border-spacing:0;}
.tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
overflow:hidden;padding:10px 5px;word-break:normal;}
.tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;}
.tg .tg-73oq{border-color:#000000;text-align:left;vertical-align:top}
</style>
<table class="tg">
<thead>
<tr>
<th class="tg-73oq">Type</th>
<th class="tg-73oq">Object Name</th>
<th class="tg-73oq">Object Number</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tg-73oq">Rubberboat</td>
<td class="tg-73oq">Life-raft, no ballast system, no canopy, no drogue</td>
<td class="tg-73oq">27</td>
</tr>
<tr>
<td class="tg-73oq">Fiberglassboat</td>
<td class="tg-73oq">Skiff - v-hull bow to stern (aluminum, Norway)</td>
<td class="tg-73oq">47</td>
</tr>
<tr>
<td class="tg-73oq">Ironboat</td>
<td class="tg-73oq"><span style="font-weight:400;font-style:normal">Skiff - v-hull bow to stern (aluminum, Norway)</span></td>
<td class="tg-73oq">47</td>
</tr>
<tr>
<td class="tg-73oq">Woodenboat</td>
<td class="tg-73oq">Skiff - v-hull bow to stern (aluminum, Norway)</td>
<td class="tg-73oq">47</td>
</tr>
<tr>
<td class="tg-73oq">Fishing Vessel</td>
<td class="tg-73oq">Fishing vessel, general (mean values)</td>
<td class="tg-73oq">50</td>
</tr>
<tr>
<td class="tg-73oq">Person in the Water, unkown state</td>
<td class="tg-73oq">Person-in-water (PIW), unknown state (mean values)</td>
<td class="tg-73oq">1</td>
</tr>
<tr>
<td class="tg-73oq">Person in the Water, concious</td>
<td class="tg-73oq">PIW, vertical PFD type III conscious</td>
<td class="tg-73oq">2</td>
</tr>
</tbody>
</table>
<h3>Radius</h3>
<p>The Simulation spawns 100 particles in a circle around the entered position. The radius controls the size of the circle. If you are uncertain about the position of an object you can increase the radius. The result will be more spread out, too.
</p>
<p>A position reported by an aircraft is typically precise to 1 nautical mile, that corresponds to a radius of 926 meters. A position reported by GPS can be very precise and corresponds to a radius of 5m. </p>
<h3>E-Mail Interface</h3>
<p>
If you have a low bandwidth connection, you can use the e-mail interface. The simulation parameters can be set in the e-mail subject. Your e-mail address needs to be registered for you user account in this tool first. The result of the simulation will be sent to your e-mail address within a couple of minutes.
Expand All @@ -18,14 +80,6 @@ <h3>E-Mail Interface</h3>
Send the mail to <pre>{{ SERVER_EMAIL }}</pre>
</li>
</ol>
The default object type for simulatoins is a life raft (ID: 27). Some alternatives are:
<ul>
<li>Person in Water (unknown state): 1</li>
<li>Person in Water (conscious): 2</li>
<li>Person in water (deceased): 6</li>
<li>Life raft: 27</li>
<li>Skif, V-hull: 45</li>
</ul>
<h3>Interpreting Simulation Result</h3>
<p>
When the simulation is finished, you will receive an e-mail that contains an attached image with the simulation results.
Expand All @@ -39,4 +93,65 @@ <h3>Interpreting Simulation Result</h3>
<p>
The image shows the trajectories of particles from the starting points to the ending points. The color of the trajectories incdicates the position of a particle at a given time. For example the color green always shows the position of the particles after ~50% of the simulated time range, while orange shows the positions at ~75%.
</p>
{% endblock content %}
<h3>Example</h3>

<p>
This is a fictional case as an example of how this tool can be used.
</p>
<p>
You open the leeway tool in the browser, and fill out the form:
It is the 4th Jan 2023 12:34 local time and you are being alerted by an airplane about fishing vessel adrift in position 37° 30'N 18°37'E. Your position is 38° 10.1532'N 018° 33.3832'E, that means you are 40nm away and with your top speed of 10kts it takes you 4 hours to reah the last known position. The contact to the drifting vessel is lost and the airplane can not stay on scene so you decide to run a drift simulation.
You open the leeway webtool and start to fill out the form:
<style type="text/css">
.tg {border-collapse:collapse;border-spacing:0;}
.tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
overflow:hidden;padding:10px 5px;word-break:normal;}
.tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;
font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;}
.tg .tg-73oq{border-color:#000000;text-align:left;vertical-align:top}
.tg .tg-0lax{text-align:left;vertical-align:top}
</style>
<table class="tg">
<thead>
<tr>
<th class="tg-73oq">Latitude</th>
<th class="tg-73oq"><span style="font-weight:400;font-style:normal">37° 30'</span></th>
<th class="tg-0lax">-&gt; Last known Latitude</th>
</tr>
</thead>
<tbody>
<tr>
<td class="tg-73oq">Longitude</td>
<td class="tg-73oq"><span style="font-weight:400;font-style:normal">18°37'</span></td>
<td class="tg-0lax"><span style="font-weight:400;font-style:normal">-&gt; Last known Longitude</span></td>
</tr>
<tr>
<td class="tg-73oq">Object type</td>
<td class="tg-73oq"><span style="font-weight:400;font-style:normal">Fishing vessel, general (mean values)</span></td>
<td class="tg-0lax">-&gt; It was reported that it is a fishing vessel, but we do not know the exact type of fishing vessel so we choose general</td>
</tr>
<tr>
<td class="tg-73oq">Start time</td>
<td class="tg-73oq">2024-01-04 11:34:00</td>
<td class="tg-0lax">-&gt; The last position was reported at 12:34 local time, that is 11:34 in UTC</td>
</tr>
<tr>
<td class="tg-73oq">Duration</td>
<td class="tg-73oq">4</td>
<td class="tg-0lax">-&gt; You calculated that it takes you 4 hours to reach the last known position so you use that as the duration of the simulation. You could also choose a bit more but the result becomes harder to interpret.</td>
</tr>
<tr>
<td class="tg-73oq">Radius</td>
<td class="tg-73oq">1000</td>
<td class="tg-0lax">-&gt; The position was reported by an airplane and only precise to the degrees minutes so you keep the default radius of 1000m. </td>
</tr>
</tbody>
</table>
</p>
<p>
You recive an Email with the simulation result. It is clear the the boat is likely to drift North to South-East-East so you set your course to 171 to position 37.5°N 18,68°. From that point you should be able to spot the drifting vessel if the weather conditions are good.
<img src="555af619-11b3-462e-b560-78764290d2f7.png" alt="Simulation result example">
</p>

{% endblock content %}

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