Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!uunet!infonode!ingr!b11!phil
From: phil@b11.ingr.com (Phil Johnson)
Newsgroups: sci.electronics
Subject: Re: More Data xfer UNDERWATER !
Message-ID: <1991Apr4.193739.15548@b11.ingr.com>
Date: 4 Apr 91 19:37:39 GMT
Article-I.D.: b11.1991Apr4.193739.15548
References: <446.27f9b921@brb.isnet.inmos.co.uk>
Reply-To: phil@b11.UUCP (Phil Johnson)
Organization: Intergraph Corp. Huntsville, AL
Lines: 36

In article <446.27f9b921@brb.isnet.inmos.co.uk> robw@brb.isnet.inmos.co.uk writes:
>>I need to transmit some data between two systems about 10 feet apart
>>without being physically connected.  
>>They will not always be line-of-sight, and they may be UNDERWATER !

  This response is made with the assumption that the data collection stations
  are underwater.

>  The data being gathered is water temperature, currents, light levels
>  and depth.

   If you are gathering current water termperature, vertical and horizontal
   current direction and velocity, ambient light level, and sensor platform
   depth with an associated time stamp the data should fit into a 50 to 100
   ASCII bytes packet (including the unit id tag field). If you sample (again
   making assumptions) at 1 second intervals and transmitting the sample data
   every minute to the master station the transmitted sample (uncompressed)
   would be approximately 3000 bytes long.  Utilizing a compandar (compress/
   expander) technique (hardware or software) this packet should be reduceable
   by at least 50 % to a size of approximatelly 1500 bytes.  Transmit this
   compressed data packet via a low frequency sonar system, such as the old 
   UQC underwater telephone.  This type of setup should provide transmission
   ranges up to 2 miles.  I don't believe the 1200 baud bandwidth will be a
   problem using this type of system.  The operational depth is of concern
   mainly for selecting the specific transducer.  Perhaps you could acquire
   UQC transducers from a used supply dealer.  The UQC transducer definitely
   worked below 100 meters. 

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| Philip Johnson                           net: phil@ingr.com                |
| Intergraph Corporation                   fax: 205-730-6445                 |