Hello John I have used ArcPad off and on, and have ignored the datum transformations you mention. Your question made me think I better check it out more carefully...
It seems that, due to local distortions in the ADG66 coordinate system, regional parameters are needed to keep transformation results (from WGS84/GDA94 to AGD66) from having excessive errors. The parameters in ArcPad appear to be from the "Geocentric Datum of Australia Technical Manual" and are considered "medium-accuracy" transformations which will be within 1m. Luckily for me, the first transform is for Tasmania (TranID = 1594) where I work. The others are: 1595 = Northern Territory , 8395 = ACT, 8397 = ?, 8399 = NSW/Vic. Perhaps 8397 is for Qld, SA or WA. Note that the two other transforms are for lat/lon coordinates. Hope this helps. Peter -----Original Message----- Message: 5 Date: Sun, 5 Feb 2006 18:29:36 +1100 From: "John Elliot" <[EMAIL PROTECTED]> Subject: [MI-L] Off Topic - ArcPad To: "MapInfo" <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="iso-8859-1" I am hoping somebody on the list may have experience of ArcPad and the datum transformations contained in the program. I want ArcPad to display Australian AMG66 coordinates as they are recorded in the field with a attached GPS unit. I have set the GPS protocol to WGS84. I now find that ArcPad lists 7 transformations associated with what are listed under "D_Australian 1966". I assume that D_Australian 1966 refers to AMG66 but there is nothing I can find that confirms this. There is also nothing to indicate what the 7 listed transformations actually are. One of these transformations, if I understand correctly, has to be linked with the projection file for the map I am using in order to show the AMG66; but which of the 7 transformation files is the correct one? I have loaded projection file AGD 1966 AMG Zone 55.prj with my ArcPad map and now am trying to figure out which of the 7 transformation files is the correct one. I have have downloaded an ArcPad paper, Map Projection Tables.pdf , which deals with transformation files. However, all the listed Australian transformations appear to refer to transformations to WGS84. I can find nothing listed that lists transformation from WGS84 to AMG66 which are the coordinates I want my GPS to display. I've clearly failed the ArcPad aptitude test, or are all ArcPad features as obscure as this seems to be. I'd be grateful for any help. John John Elliot Bathurst, NSW 2795, AUSTRALIA ------------------------------ _______________________________________________ MapInfo-L mailing list [email protected] http://www.directionsmag.com/mailman/listinfo/mapinfo-l
