[APG Public List] [APG Members] place names

LBoswell laboswell at rogers.com
Tue Oct 26 07:31:20 MDT 2010


excellent explanation.  I should have twigged to the idea that the 
coordinates could be adjusted to refer to a larger area.  That removes one 
of the problems about how to deal with something like an entire township or 
a general area.

Even more interesting, by adjusting the coordinates you could reference an 
area that covered a couple of jurisdictional boundaries.

Using coordinates as well as place names would take care of the argument as 
to whether the historical or the modern name should be used.  It's an area 
that needs some guidelines, and explanations like this are a step towards 
establishing them

Larry
  ----- Original Message ----- 
  From: Jacqueline Wilson
  To: apgpubliclist Posting ; apgmembersonlylist at apgen.org
  Sent: Tuesday, October 26, 2010 8:59 AM
  Subject: Re: [APG Public List] [APG Members] place names


  Stephen - thank you for pointing out how GPS numbers are coded.  Learn 
something new every day!


  On Oct 26, 2010, at 1:29 AM, Stephen Danko wrote:


  GPS coordinates can be specified so that they represent either a large 
general area or a spot the size of a pinpoint.  It's all in how many 
significant figures one lists in the coordinates.

  The number of significant figures refers to the number of numerals in the 
coordinate.  37.79507, -122.40280 has 7 significant figures in the N-S 
coordinate (the first number) and 8 significant figures in the E-W 
coordinate (the second number).  This is the location of the Transamerica 
Pyramid in San Francisco.  Actually, it is the location of a part of the 
Transamerica Pyramid.  This coordinate has so many significant figures that 
it points to a very accurate location on the earth.  If the coordinate is 
written as 37.8, -122.4, the area described becomes much larger and includes 
anything between 37.75 to 37.84, -122.35 to -122.44.  Written as 
37.8, -122.4, the coordinates don't accurately specify the Transamerica 
Pyramid, but instead specify about half of San Francisco.

  Note that 37.8, -122.4 is not the same as 37.8000, -122.4000.  The first 
set of coordinates gives a general location (the eastern half of San 
Francisco) and the second set gives a very specific location (the corner of 
Vallejo and Front Streets in San Francisco).

  The latitude longitude system we use today is based on a prime meridian 
through Greenwich, England.  Historically, different places used different 
prime meridians (including prime meridians in Paris, Washington, D.C., and 
Rio de Janeiro).  For genealogical purposes, all historic systems can be 
ignored and we can use today's system with a prime meridian through 
Greenwich because, as Larry pointed out, our goal in using latitude 
longitude coordinates is to specify where a place is today, using today's 
system.  Using GPS coordinates, Nicole (in a different thread) would have 
immediately been able to find out where Grossendorf, Germany was, and she 
would have immediately been able to see that the present name of the place 
is Władysławowo, Poland.

  True latitude/longitude coordinates are not exactly the same as GPS 
coordinates.  This is because GPS uses the International Reference Meridian 
which is 102.5 meters east of the Prime Meridian through the Royal 
Observatory in Greenwich.  Don't worry about the reason for this difference. 
Google Earth used GPS coordinates instead of true latitude longitude 
coordinates, presumably so that GPS systems will match up with Google Earth.

  In summary, GPS coordinates can be used to describe a very specific point 
on the earth or a very general area of the earth depending on the number of 
significant figures in the coordinates.

  Kind regards,
  Stephen J. Danko
  http://www.stephendanko.com/




------------------------------------------------------------------------------
  From: Connie Sheets <clsheets1 at yahoo.com>
  To: apgpubliclist at apgen.org; apgmembersonlylist at apgen.org
  Sent: Mon, October 25, 2010 4:33:55 PM
  Subject: Re: [APG Members] [APG Public List] place names

  I must admit to only a general knowledge about, and frequent lack of 
attention to, GPS coordinates.  I have been operating under the assumption 
they describe a specific point on the earth, not a large area like a rural 
US township of 36 square miles.

  I can comprehend how I might want to visit the crossroads approximately 
one mile southeast of a very small village in Northwest Missouri where my 
great-great grandfather's house once stood, obtain the GPS coordinates, and 
record them for posterity with a photograph I have of the house.  I also 
understand how GPS coordinates are useful for locating cemeteries, graves 
within cemeteries, and other landmarks.

  However, if all I know about an ancestor's location is a rural township or 
county, I would be concerned that I was promoting inaccuracy if I 
arbitrarily chose (and yes, it would be arbitrary) the center of the 
township or county.

  I will continue to use standard historical place names, with a reference 
to the modern place name when necessary, for the foreseeable future.

  Connie Sheets
  Arizona


  Jacqueline Wilson
  Evanston, IL




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