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Author Topic: Wrong datum for Hawaii in ibycus USA 2.0  (Read 5030 times)

DaKine

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Wrong datum for Hawaii in ibycus USA 2.0
« on: May 29, 2009, 09:28:17 PM »
I loaded the Hawaii Topo and the and Ibycus USA 2.0 onto my Colorado and then compared the maps.  My location relative to the roads on the maps was different and the shift looked to be about the same as the shift between NAD 27 and NAD 83 datums.  My position on the ground matches the Hawaii Topo map but not the Ibycus map.

As a check, I looked at the coordinates for the intersection of Koloa Rd and Kaumualii Highway in Kauai in MapSource.  Ibycus shows the coordinates as N 21 55.764 W159 30.661 and the Hawaii Topo shows N21 55.578 W159 30.496.  I shifted the Ibycus coordinates from NAD 27 to NAD 83 using the National Geodetic Survey program NADCON http://www.ngs.noaa.gov/TOOLS/Nadcon/Nadcon.html.  The shifted coordinates are N21 55.575 W159 30.493.  It looks like the Ibycus data for Hawaii is in the NAD 27 datum.

maps4gps

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Re: Wrong datum for Hawaii in ibycus USA 2.0
« Reply #1 on: May 30, 2009, 03:56:39 AM »
The 2007 March Census data did not have all the islands converted to NAD83.  Oz noticed this and made the corrections when he created his Hawaii Topo.

DaKine

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Re: Wrong datum for Hawaii in ibycus USA 2.0
« Reply #2 on: May 30, 2009, 11:25:40 PM »
The OMS map looks to also be in NAD 27.  It shows the intersection coordinates as N21 55.766 W159 30.664.  The state of Hawaii GIS department has shape files for the TIGER data.  Links to the data are available at this site http://hawaii.gov/dbedt/gis/download.htm.  The site has TIGER and USGS road data for the entire state along with County sponsored data for Hawaii County, Kauai County, Maui County and The City and County of Honolulu (Oahu and Lanai). 

I have worked with the TIGER data for Kauai in the past and the TIGER data did not distinguish between paved and dirt roads.  The Kauai County provided data is GPS derived but the metadata file for Hawaii County says it is rectified to parcel data and is not positionally accurate.  the best approach is probalby to use the NAD 83 TIGER data from the site and augment it with County data if it is better.  I suppose I should volunteer to convert the data and make it available for an update to ibycus and OMS.  I see that there is a SHP to IMG converter.  I will need to learn a bit about the process and what extra work is required for routeable maps.  I am heading to Seattle on vacation in a few days so I won't be able to get to this for a while.

-Oz-

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Re: Wrong datum for Hawaii in ibycus USA 2.0
« Reply #3 on: May 31, 2009, 05:09:02 PM »
thanks for the link; i can use that to update the hawaii topo too...
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leszekp

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Re: Wrong datum for Hawaii in ibycus USA 2.0
« Reply #4 on: June 05, 2009, 12:05:24 PM »
Always wondered where Hawaiians went on vacation  :).

Indrid Cold

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Re: Wrong datum for Hawaii in ibycus USA 2.0
« Reply #5 on: June 05, 2009, 04:34:23 PM »
Always wondered where Hawaiians went on vacation  :).
When I lived there it was Las Vegas ;D

DaKine

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Re: Wrong datum for Hawaii in ibycus USA 2.0
« Reply #6 on: June 06, 2009, 05:52:15 AM »
Most Kama'aina go to Vegas, just isn't my thing.  We moved from Seattle, and I still prefer the northern forests to neon lights and loud smokey casinos.

Indrid Cold

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Re: Wrong datum for Hawaii in ibycus USA 2.0
« Reply #7 on: June 06, 2009, 05:57:44 AM »
Most Kama'aina go to Vegas, just isn't my thing.  We moved from Seattle, and I still prefer the northern forests to neon lights and loud smokey casinos.
Not my thing either. I preferred to visit the outer Islands. Loved hiking Kauaʻi.