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    Re: errors in plotting and a possible/partial fix thereof, as menti...
    From: Jeremy C
    Date: 2010 Dec 29, 09:34 EST
    That is good advice Alan.  I had never thought of using harder lead.  I will have to bring a few sticks out with me on my next trip.  If you can believe it, when i was a college freshman in 1994, i actually took manual drafting and still have sticks of the harder leads which i used in mechanical pencils.  They are all 0.5mm leads.  Still I was never good at drafting or any sort of drawing which causes me to be wary of my celestial plotting compared to the computer's work.
     
    I am not familiar with the PS sheets by that name.  I suspect they are either similar to, or exact copies of what I call the "Universal Plotting Sheet" denoted with VP-OS on the side.  It has a compass rose in the middle and a central meridian line scaled in 1' of latitude and can cover 4 degrees of latitude.  In the lower right corner is a scale to calculate the scale of longitude based on the mid-latitude selected.
     
    The Latitude scale on my sheet is about 1.1mm per minute.  The longitude scale varies considerably with about 1.25mm per minute of Longitude at the equator and 0.5mm per minute at 70 degrees Latitude.
     
    In either case, my 0.5mm lead is going to cause some ambiguity with the fixes and perhaps I can cut that in half by sharpening the lead.  Still my issues tend to revolve around the numerous motions of my triangles.  
     
    If I am using the GPS fix as the AP, I first have to advance and retard each of the stars along the track line.  The trouble then becomes that I have such small intercepts it is difficult to mark them accurately (my normal dividers leave a 2mm gap between points).  My other dividers have much larger points which are also not as accurate.  Then I have to spin the triangles from the azimuth to the LOP angles and i always get a bit of error trying to get the exact distance from the AP.  Do this over 5 stars and so, and the error just starts to compound.
     
    Doing it the old fashion way with tables, I run into the same problems when i advance or retard the AP's on the whole degree of latitude and then star plotting. 
     
    My only other option is to use a larger scale chart which isn't normally available for the ocean regions.
     
    I still practice with my manual plotting, but when actually navigating the ship, i use the transferred position from the computer.
     
    Jeremy
     
    In a message dated 12/28/2010 3:10:12 A.M. Central Asia Standard Tim, alan202@verizon.net writes:

    Jeremy:

    Re errors mentioned regarding your efforts at MANUAL PLOTTING, as an old ex draftsman, the following comes to mind.

    Assuming that you are using the old #2 pencil, the lead therein is pretty soft, sharpen it often, try using a "draftsmans pencil sharpener/pointer" and fine sand paper or a fine cut flat file. Also use a light hand when drawing lines.

    If you use a "machanical pencil" actually a device that holds stick leads, again use a sharp point, along with a light hand. You might try a harder lead too. Leads designated H as in 2H, 3H get harder as numbers get higher, B series leads get softer, the HB lead is about equivalent to # 2 lead pencils. As I recall, 2B, 3B would be getting softer.

    Should you opt for the "Pentel Pencils", actually lead holders, try the 0.5mm diameter, the thinnest offered, use a hard lead, with a light hand. With the smaller diameter leads, hold the pencil close to vertical, as these small diameter leads tend to snap.

    I don't know what sort of a plotting sheet you use. For my purposes, the Power Squadron Constant Latitude Sheet (CLS98)serves, however as to reading latitudes, strikes me that the limit is .5 NM, though someone with younger eyes might be able to read to .25NM, though I think this is something of a stretch. As for the longitude scale, about .5 minutes seems to be a stopping point, though again, younger eyes might better this.

    Of course, if using a computer program to "plot" lop's, the computer's read out is in coordinates, lat. and long. isn't it. Ergo, no problems with the thickness of a pencil line.
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