Dan, You're correct, the no-datum Lat/Long will take the datum of whatever projection is being used by a map window. For example, if you have a Lat/Long WGS84 table open, and then open a no-datum Lat/Long table, MI seems to assume that the no-datum coordinates are WGS84. Cheers, _____________________________ Tim Warman Groundwater Geologist/GIS Guy Richard C. Slade & Associates LLC North Hollywood, CA, USA +1 (818) 506 0418 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of [EMAIL PROTECTED] Sent: Monday, June 04, 2001 7:00 AM To: Robert Crossley Cc: MapInfo List Subject: Re: SUMM: MI-L Problems with WGS 84 projections in a map display Is this correct that if a table is in Lat/Long projection with no datum associated in the projection list , MI will imply that it is in NAD27 and recalculate the coordinates from Nad27 to the new selected projection? I always assumed that if data is in Lat/Long with no datum selected in the projection list, and if and when a new map projection is set it will not change or recalculate anything but simply associate that newly selected datum to that data set. Then if you decide to change the projection after that then it will recalculate the coordinates to a new projection. I'm I wrong, can someone clear this up for me? TIA Dan "Robert Crossley" <[EMAIL PROTECTED]> on 06/01/2001 03:12:31 PM Please respond to "Robert Crossley" <[EMAIL PROTECTED]> To: "MapInfo List" <[EMAIL PROTECTED]> cc: (bcc: Dan Page/HullOttawa/PCH/CA) Subject: SUMM: MI-L Problems with WGS 84 projections in a map display Thanks to Willy from Denmark for advice on this one: >> I have found that you should never, ever use the Lat/Long without datum. Apparantly MI being an US application then thinks that it implies, that the NAD 27 was used in calculation of the coordinates. So if no datum is specified even if the coordinates are to e.g. WGS84 MI will recalculate the coordinates from NAD 27 to WGS 84 if the map projection is set to WGS 84 giving an error of several hundred meters. I am still working on it, but this seems to be the key. Sorry Dave, your answer was not correct and you must leave now.... Thanks anyway. Robert. _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body. _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body. _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
