FW: shrug-l: NAD83/90

Thomas, Jim jim_thomas at golder.com
Wed Sep 6 13:32:12 EDT 2006


I've done more research and the 90 part of NAD83/90 seems to refer to
the 1990 adjustment (as John said below).  This is new to me as I've
never referred to NAD83 in another way.  Does anyone know what the
latest adjustment is?  and what ESRI's ArcGIS uses?
 
I'll have to do more homework on this one.  Thanks for your help.

________________________________

From: Sykes, John [mailto:John.Sykes at dep.state.fl.us] 
Sent: Wednesday, September 06, 2006 11:59 AM
To: Thomas, Jim
Subject: RE: shrug-l: NAD83/90


My understanding is that the NAD83 is the "standard" replacement for
NAD27.
 
NAD83 HARN and NAD83/90HPGN are, essentially, the same.  Originally it
was called the High Precision Geographical Network, but was subsequently
changed to High Accuracy Regional Network (or something like that).
 
The difference between NAD83 and NAD27 is several meters (up to around
100 meters in parts of Florida), but NAD83 to NAD83 HARN is usually in
the centimeter range (in most of Florida).
 
Note:  It is also my understanding that the NAD83/90 is the "standard"
version of NAD83 and, therefore, is redundant.  So usually you would see
just NAD83 or NAD83 HARN, the "90" is assumed (not necessarily the case
with HARN, which I believe is set to a later epoch [2004????]).  HPGN is
no longer used.  If you want to confirm the epoch, look up a CORS
station in the NGS datasheets, it will give the epoch information as
well as the drift information (Florida is drifting northwest at about 1
cm/yr).

-- John 

 

________________________________

From: shrug-l-bounces at lists.dep.state.fl.us
[mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Thomas, Jim
Sent: Wednesday, September 06, 2006 11:27 AM
To: shrug-l at lists.dep.state.fl.us
Subject: shrug-l: NAD83/90


Can someone briefly explain the difference among the following.
 
NAD83
NAD83 HARN
NAD83/90 HPGN
 
Is NAD83 HARN the same as NAD83/90 HPGN?
 
I'm getting requests to have coordinates reported in NAD83/90 and need
to understand the difference.
 
Thanks for you help.
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