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Date: Tue, 20 Jul 1999 14:00:18 -1000
From: Ross Togashi <[log in to unmask]>
Subject: USGS' Hawai'i Revision Project - datum shift
Sender: Ross Togashi <[log in to unmask]>
Aloha,
This message is of concern to map libraries, particularly those
that receive revised USGS topographical quad maps of the State of
Hawai'i through the Federal Depository Library Program (FDLP).
It will be of interest to users of these Hawai'i topo quads, DRGs,
and DLGs, as well.
The 7.5 min. quad maps of Hawai'i are being recast from the Old
Hawaiian Datum, used on previous revisions, to the more accurate
North American Datum of 1983 (NAD83). With this change in datum,
the sheet boundaries will shift slightly. These new maps (and the
new DLGs and DRGs) will therefore not matchup with the older map
boundaries.
If your map library is withdrawing older editions as the newer
sheets are received and added, a common practice among many FDLP
map libraries, you may be losing map data (at least temporarily)
until adjacent sheets are later received in future depository
shipments.
Vicki Lukas of the USGS has been very kind in providing a webpage
that describes the Hawai'i Revision Project and among other very
interesting things, addresses this map concern regarding the datum
shift.
If you are interested, please take a look:
ftp://pokey.wr.usgs.gov/pub/avaughn/CR_DATA/revision/index.html
For an example of the implications of all this, let me ask you to
pull out the HILO 1995 ed. (s.l. 98-23), and adjacent MOUNTAIN VIEW
1982 quadrangles. Note that when you try to match these two map
sheets, a narrow band of area along the south margin of the Hilo
sheet is now "missing", along with a large part of my home town of
Keaau. If you've withdrawn the 1982 HILO sheet from your collection,
you are out of luck UNTIL you receive the MOUNTAIN VIEW sheet sometime
in the future.
Again, my thanks to Vicki Lukas of USGS for her assistance in this
matter, and for setting up that informative website.
Aloha,
Ross
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Ross Togashi, Map Technician
University of Hawaii at Manoa http://www2.hawaii.edu/~mapcoll/
Hamilton Library - Map Collection E-mail: [log in to unmask]
2550 The Mall Phone: (808) 956-6199
Honolulu, HI USA 96822 Fax: (808) 956-5968
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
mmm...spamoroni
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