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| Subject: | Re: GISList: Hawaii GIS |
| Date: |
08/01/2002 03:05:09 PM |
| From: |
Hylan L Beydler |
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****Posted for non-list member Craig Manning, U.S. Geological Survey***
Please include cmanning@usgs.gov in responses you may submit.
Craig E Manning 08/01/2002 08:38AM
NAD27 was established at a time when we did not have the tools we have
today to establish NAD27. I'm sure there are much less "kindergarten"
explanations out there. If there was anything Rocket Science about making
maps, Horizontal Datums are it. I know though, that a separate datum was
established for Hawaii, as I am to understand, one for Puerto Rico as well.
Alaska, too, has similar problems when comparing NAD27 to NAD83.
What happens here with USGS products where we cannot revise and change them
all overnight, especially on-shelf products or extensive databases like
GNIS,
or products like DRG's, there will be a fallout that becomes amplified
because
people can visually see the differences between the new datum and the old.
The
worst differences will be with the remotest reaches of the US and it's
territories. But it was the best we had at the time.
GNIS began name collection with Phase I compilation using all USGS on shelf
map products. Phase I was completed in 1981, 2 years before NAD83. 55,800
maps, 7.5', 15' and 1:250K was the order of preference if my memory
serves me correctly. We're talking approximately 1 million of the 2
million name records currently in the GNIS database. So, much of what
you find in the named features existing today in GNIS will be with
coordinates that are based on the NAD27. One thing to note, GNIS was
collected with a + or - 500ft tolerance on coords, due to paper shrinkage
with stored maps. As far as the datums go, in the Central US and East,
the differences with NAD83 will be minor.
The resolve here is to participate in the updating of the GNIS database
to correct these features with the gross NAD errors. Hawaii, California,
Oregon, Washington, and Alaska probably with the grossest differences.
Many of those states have had some changes made. On-line web forms are
being built and beta tested as we speak and there will soon be in place a
redesigned GNIS database, spatially enabled as well and may correct alot
of this by that alone. However, anyone with the necessary logon and
password,
approved by the Reston, VA USGS GeoNames Office will be able to submit
corrections and assist in fixing this problem.
Craig E. Manning
U.S. Department of Interior
Geological Survey
Geographic Names Information System
Mid-Continent Mapping Center
1400 Independence Rd.
MS-900
Rolla, Missouri 65401
cmanning@usgs.gov (W)
cmanning@wavecomputers.net (H)
(573)308-3839 (W)
These two messages come from the mailing list at GeoComm (GISData Depot).
If anyone has any input, please email the list at: gislist@geocomm.com
Thanks, Hylan
----- Forwarded by Hylan L Beydler/NMD/USGS/DOI on 07/31/2002 02:58 PM
-----
Mike Flannigan
<mikeflan@earthl To: gislist@geocomm.com
ink.net> cc: Thomas Harris <thomas@globalecology.stanford.edu>
Subject: Re: GISList: Hawaii GIS
07/31/2002 01:35
PM
It sounds very familiar. I noticed on a trip to Hawaii this year that
the entire GNIS database of features is off by the same, consistent,
~100 meters you notice. As I recall, features are really east of the
location given in GNIS. Not sure what the problem is, but I
suspect it is datum related. GNIS appears to be NAD27 for the
lower 48, but it's not well documented in my version.
Mike Flannigan
Thomas Harris wrote:
> Hi List:
> We are having some difficulty with out Hawaii GIS. I received USGS
> DRG's that are in UTM NAD27. Overlaying our Hawaii roads coverage
> reveals a uniform offset in the DRG data of over 100 meters. We have
> confidence in our road data because of field validation with GPS. I
> suspect that the problem is perhaps unique to Hawaii. Does this
> problem sound familiar to anyone working with Hawaii data?
> Thanks in advance,
> Thomas
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