Will, Old Hawaiian Datum origin is at Oahu West Base where: Latitude = 21* 18' 13.89" North, Longitude = 157* 50' 55.79" West of Greenwich The reference azimuth to Oahu East Base is 291* 29' 36.0 (from South) and the ellipsoid of reference is the Clarke 1866. The Old Hawaiian Datum is based on an adjusted Latitude derived from a number of Astronomic Latitudes observed in various parts of the islands, hence the term "mean." It is also based on an adjusted Longitude derived from a number of Astronomic observations in various parts of the islands that included lunar culminations, stellar occultations, etc., hence the term "mean" also. For a detailed description of the origin, see U.S. Coast & Geodetic Survey Special Publication No. 156, "Triangulation in Hawaii." I do not have any information regarding the geometric relation between the Old Hawaiian Datum and NAD1927, but I would guess that the differences are probably minimal, mostly in Longitude, if any. (S.P. 156 would have the definitive answer, I do not have a copy.) On the other hand, the difference to NAD83 should be a whopper! Let me know if you need further help. Cliff -- Clifford J. Mugnier ([EMAIL PROTECTED]) The Topographic Engineering Laboratory Department of Civil and Environmental Engineering UNIVERSITY OF NEW ORLEANS New Orleans, Louisiana 70148 Voice and Facsimile: (504) 280-7095 ------------------------------------------------ Mitchell, Will wrote: > > Hello Cliff, > > Pardon me if this is an obvious or unwelcome question, but - can you tell me > anything about the Old Hawaian Mean datum, or refer me to good reference > material on it? > > I must admit I get quite mixed up in this arena (datums and projections). > I'm simply trying to use data in MapInfo that I believe to be State Plane > NAD27 HI Zone 3, and I don't know how NAD27 equates to Old Hawaian Mean > (this was referred to in a different data source). > > Thanks. > > Will Mitchell > GIS Manager > The Environmental Company, Inc. > Charlottesville, Virginia > 804-295-4446 > [EMAIL PROTECTED] > ---------------------------------------------------------------------- To unsubscribe from this list, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MAPINFO-L" in the message body, or contact [EMAIL PROTECTED]
