REAL-TIME INSTRUMENT SUPERVISION
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!DESCRIPTION
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When shooting a seismic line one person is normally supervising the instrumentation, and records any anomalies on log sheet. These instruments and values must be monitored:
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* Gun air pressure
* Distance off line (DOL). There is no automatic steering of ship, captain has copy of Survey Line on PC display on the bridge and follows the line as closely as possible.
* Gun controller (GUNCO)
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Of these, only the GUNCO will provide malfunction notification - it will beep. The other parameters are just displayed without any limits set. When DOL runs astray it could possibly mean interupting the line and doing a loop, re-shooting defective section. When the airgun pressure drops we eventually risk filling the guns with seawater. Their subsequent retrieval and maintenance means valuable survey time is lost.
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Naturally, it's tiring for a human operator to watch these instruments hour after hour. In addition, it's very old-fashioned. So we made a program that collected relevant information automatically and provided audible operator warning through a web interface, as shown below:
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Attach:seismic-monitor.png"Web interface automatic real-time instrument monitoring onboard RV Håkon Mosby"<br />''Web interface automatic real-time instrument monitoring onboard RV Håkon Mosby''
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The user can choose from predefined parameter limits - except for the GUNCO, where the 2 ms timing error limit is set as default. One can select different audible alarms, like a voice announcing ''"Houston, we have a problem ..."''. In addition, there's a built-in master alarm (very hard to ignore!) which is triggered when GUNCO fires with pressure less then 100 Bar, as the airguns are then in danger of beeing flooded with seawater.
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As an added advantage, those taking a keen interest in the operation of the instrument system - like the cruise leader, one would imagine - can have the webpage hidden behind other stuff on his or her computer desktop, and receive a warning of any impending trouble.
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!AUTOMATIC LOG
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The system exchanges data in XML-format. Each shot event is represented by a chunk of data, illustrated by this example listing:
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%box%<pre class='escaped'>
<EVENT NO="2956">
<TIME_RECEIVED>1244080074</TIME_RECEIVED>
<LINE>Prof2_09</LINE>
<TIME>01:47:54</TIME>
<DATE>04.06.2009</DATE>
<EASTING>120319.00</EASTING>
<NORTHING>7137456.03</NORTHING>
<LAT>064:09.191520</LAT>
<LON>001:10.782222</LON>
<DOL>-4.27</DOL>
<PRESSURE UNIT="Bar">130</PRESSURE>
<GUNCO>
<TIME_RECEIVED>1244080075</TIME_RECEIVED>
<NO_OF_GUNS>4</NO_OF_GUNS>
<GUN NO="1">
<OUT_OF_RANGE>No</OUT_OF_RANGE>
<ERROR>0.3</ERROR>
<MISFIRE>No</MISFIRE>
<DELAY>18.0</DELAY>
<OFFSET>0.0</OFFSET>
<AUTO>Yes</AUTO>
<MANUAL>No</MANUAL>
</GUN>
<GUN NO="2">
<OUT_OF_RANGE>No</OUT_OF_RANGE>
<ERROR>0.0</ERROR>
<MISFIRE>No</MISFIRE>
<DELAY>17.7</DELAY>
<OFFSET>0.0</OFFSET>
<AUTO>Yes</AUTO>
<MANUAL>No</MANUAL>
</GUN>
<GUN NO="5">
<OUT_OF_RANGE>No</OUT_OF_RANGE>
<ERROR>-0.4</ERROR>
<MISFIRE>No</MISFIRE>
<DELAY>22.7</DELAY>
<OFFSET>0.0</OFFSET>
<AUTO>Yes</AUTO>
<MANUAL>No</MANUAL>
</GUN>
<GUN NO="7">
<OUT_OF_RANGE>No</OUT_OF_RANGE>
<ERROR>0.4</ERROR>
<MISFIRE>No</MISFIRE>
<DELAY>23.1</DELAY>
<OFFSET>0.0</OFFSET>
<AUTO>Yes</AUTO>
<MANUAL>No</MANUAL>
</GUN>
</GUNCO>
</EVENT>
</pre>
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The XML formatting, albeit verbose, makes the structure pretty easy to understand.
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For each shot, this XML data block is saved to file. So when the survey line is finished, we have a file with a sequence of such blocks, permitting automatic generation of a survey log. Parsing and extracting information from this XML file requires some programming. We will attend to this as time permits.
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