I mentioned that I was checking out transformations
between latitude & longitude in NAD-27 and NAD-83, etc..
Below is a quote that came up with a google search
for something like
"datum transformation nad27 nad83 latitude longitude"
if I recall correctly.
"Background:
Downloading GPS data stored in WGS84/NAD83 datum
and displaying them with GIS data in NAD27 datum
can result in a 100's of meters in error!"
<www.nps.gov/gis/gps/gps4gis/how2s_byCatagories/>
"Corpscon is one of our favorites...
US Army Corp of Engineers - Corpscon for Windows...
uses the US NGS NADCON algorithm"
Free download (9.8MB) from
<
http://www.gisuser.com/index.php?option=com_remository&Itemid=105&func=
fileinfo&parent=category&filecatid=225>
or <
http://tinyurl.com/5mfc2>
See also the AKSO (Alaska US National Parks Servive)
cheatsheet called "CorpsconUse.doc" for instructions (MS Word)
<
http://www.nps.gov/gis/gps/aksogps/GenGPSToolKit03/Cheatsheets/Corpscon
Use.doc>
or <
http://tinyurl.com/65lf9>
I've added and tested "Datum Transformations" bookmarks
for CORPSCON and the cheatsheet to BP.
The letter from Gary Jeffress on legal aspects of maps
and suggesting lat & long to 3 decimal digits of seconds
was _very_ interesting. That gives us some indication
of how well a pro can do using pro gear
and how to judge some of the web sites and programs
that spit out many, many digits. Such results
may (or often may not) be mathematically correct,
but are meaningless in the real world of measurements.
Starting this week and continuing to the end of the year,
we will be away from home for 3 days a week many weeks
and out of internet access. Usually I end up getting
_way_ behind in email and end up having to delete
unread most of the many email digests to which I subscribe. :(
So if anyone has a direct question or comment for me,
send a direct personal email to my address.
"aletheiak" says,
"...happily our mathematical needs & challenges
are ever changing as well as never ending..."
Wouldn't have it any other way. :)
Have fun.
Cheers, 73,
Ron McC.
w2iol@...
Ronald C. McConnell, PhD
WGS-84: N 40º 46' 57.6" +/-0.1" W 74º 41' 22.1" +/-0.1"
NAD-27: N 40º 46' 57.2" +/-0.1" W 74º 41' 23.5" +/-0.1"
FN20ps.77GU31 +/-
V +5058.3438 H +1504.2531 +/-
http://home.earthlink.net/~rcmcc
"Not everything that counts can be measured
and not everything that can be measured counts"
- Albert Einstein
Go Hokies!!