Tanks, but we has a problems, now the new projection is a ITRF, We do not find information about that,
Please if you has any information, send us. Regards Alfonso Ochoa ----- Original Message ----- From: "Natalie Green" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, March 21, 2002 10:25 AM Subject: [geonet]: DNAG data projection on the DAP server > Dear Geoneter's, > > It has been pointed out that DNAG gravity and magnetic data retrieved from > the Geosoft DAP server does not reproject correctly when displayed on maps > that are not in the native DNAG projection. We will be loading a new, > re-projected DNAG data set on the server by March 28 that gets around this > problem. > > Following is an explanation of why this happens for the projection-aware out > there... > > The DNAG data uses a coordinate system based on a spheroid (called STM1987), > which is not a standard datum, such as NAD27. Since most of the data in the > compilation was in some projection on NAD27, all data was first converted to > longitude, latitude on NAD27. These NAD27 geographic coordinates were then > assumed to be located at the same latitude, longitude on the STM1987 > spherical datum. The latitudes should have changed when converting from the > NAD27 ellipsoid to the STM1987 spheroid. However, the DNAG group probably > found it was convenient to use NAD27 latitudes because converting back to > latitude, longitude yields the correct location on a NAD27 datum. Modern > software like Geosoft naturally changes the latitude, longitude when > changing between datums, which results in the location problem people have > observed. > > We are correcting this problem by loading a properly projected DNAG data set > that includes the correction for latitude, longitude shift between datums. > > Please be aware that any use of the DNAG data retrieved on the DAP server > prior to March 28 will mislocate features by up to 20 km in the North-Sout h > direction. > > Please contact your local support representatives for more information. > > Kindest regards, > Natalie Green > > ____________________________________________ > > Natalie Green > Technical Support > [EMAIL PROTECTED] > > Geosoft Latinoamérica Ltda. > Av. Rio Branco, 156 Gr. 2615 - Centro > Rio de Janeiro - RJ - BRASIL - 20043-900 > Tel: 55 21 2532-0140 Fax: 55 21 2532-7197 > > Knowledge from data. > Free Oasis montaj interface with public-domain Data Access Protocol (DAP) > for accessing high-volume spatial data over the Internet available for > download at www.geosoft.com/pinfo/free/downloadfree.html > _______________________________________________________ > More mailing list info http://www.geosoft.com/support/listserv/index.html _______________________________________________________ More mailing list info http://www.geosoft.com/support/listserv/index.html
