| my account | login-logout | resources | support | catalog | home | get webcard |

Online Classroom

Post New Topic  New Poll  Post A Reply
search | help desk | commons
  next oldest topic   next newest topic
» Online Classroom   » Celestial Navigation   » Public Discussion of Cel Nav   » plotting sheets - larger scale?

Author Topic: plotting sheets - larger scale?

 - posted April 04, 2020 05:17 PM      Profile for bruce           Edit/Delete Post 
I'm working through some of the problems in Hawaii by Sextant, and it occurred to me that in a lot of cases it would be handy to have plotting sheets that are at a larger scale.

The standard plotting sheets are effectively 4 degrees on each access (roughly 240 nm x 240 nm)... this is great for a running DR plot and fixes over a day or more, but if all I'm doing is reducing a set of sights to a single position, the plot gets ... "cluttered" at this scale. For example, a 3-body fix (e.g., problem 9) doesn't need a huge area, and at the scale of a standard plotting sheet the thickness of a pencil line can make a difference in accuracy

Does anyone make plotting sheets that are, for example 2 degrees by 2 degrees? Like, with the central compass rose full-size on the sheet (13" diameter)? That seems like it could be useful for (for example) running plots where the distance traveled is 100 miles or less.

From: Everett, WA
David Burch

 - posted April 04, 2020 05:21 PM      Profile for David Burch           Edit/Delete Post 
You can label these parallels however you choose. Just do the longitude by the same amount when you do.

We often use them at 6' per parallel rather than 60' for good plots, but you can also to them at 30' as you ask about. Same sheets, just different labels... and then scale the lon nomogram the same way.

From: Starpath, Seattle, WA

 - posted April 04, 2020 06:31 PM      Profile for bruce           Edit/Delete Post 
I think I like that better. As I thought about it after posting, having the central rose 13" in diameter might become awkward to use.

So, same sheets, just remember that

-- 10' of latitude on the vertical axis is now 20' of latitude and 20nm of distance, and

-- 10' of longitude on the nomogram is now 20'

Any other tips or things to keep in mind?

From: Everett, WA
David Burch

 - posted April 04, 2020 07:48 PM      Profile for David Burch           Edit/Delete Post 
No. The only other point that comes to mind is this type of zoomed plotting works best with computed solutions in that you can use the center of the UPS as your DR and then reduce all sights from the DR and the plotting is very easy... you just have strange lines, ie lon 135º 26' and then the next one 135º 20', then 135º 14' and so on. Once practiced it all goes fast.

We have a dedicated calculator the Starpilot for this, but there are a lot of free programs that will do a simple sight reduction if you do not need all the cel nav power and piloting functions of the StarPilot—i.e., the StarPilot will plot the lines as well. The free Celestial Tools by Stan Klein is one good one, but there are many.

From: Starpath, Seattle, WA

All times are Pacific  
Post New Topic  New Poll  Post A Reply Close Topic    Move Topic    Delete Topic next oldest topic   next newest topic
Hop To:

Starpath School of Navigation

Copyright, 2003-2021, Starpath Corporation

Powered by Infopop Corporation