I can't see why you transformation as to be affine. Take a look at this PDF descriping the MapBasic application VisualHelmert doing a conformal Helmert transformation to MapInfo Vector tables.
ftp://ftp.mapinfo.dk/pub/VisualHelmert/ The helmert transformation can be used to rotate or displace a MapInfo vector table or transform a vector table from a non-earth projection to an earth projection. Jakob Lanstorp, GIS-Developer Kampsax GIS Software & Solutions, Rugaardsvej 55, 5000 Odense, DK tel: + 45 63 13 50 13, dir: + 45 63 13 50 11, fax: + 45 63 13 50 90 mailto:[EMAIL PROTECTED] , http://www.kampsax-gis.dk Authorized MapInfo Partner & Distributor in Denmark and Norway ----- Videresendt af Jakob Lanstorp/Kampsax - 16-11-01 08:16 ----- [EMAIL PROTECTED] Sendt af: Til: [EMAIL PROTECTED] [EMAIL PROTECTED] cc: onsmag.com Vedr.: MI-L Affine Transformations 15-11-01 22:40 Besvar venligst til Dan_Page Regarding my earlier post (at the bottom of this e-mail) about transforming a non earth map to a real earth coordinate system. I ended up converting the file to dxf and importing it into MapInfo and setting up a coordinate transformation using the two control points that I had. But I'm not sure how accurate this is? Does anyone know what the differences are between using this method and using the affine transformation method or using other softwares that do this kind map transformation from a non earth to a real earth coordinate system? Are some transformation methods more accurate then others? Information about software that can do this kind of transformation was also suggested such as the Traverse PC and Discover program, are there any other software packages that can do this? In what situation should one use these programs or use the affine transformation method rather then just setting up a coordinate transformation while importing a dxf version in MapInfo? Any insight would be appreciated. TIA Dan ---------------------- Forwarded by Dan Page/HullOttawa/PCH/CA on 11/15/2001 04:24 PM --------------------------- Dan Page 11/15/2001 01:25 PM To: [EMAIL PROTECTED] cc: Subject: Affine Transformations I have an AutoCad drawing of a survey that was done in non-earth coordinates "metres" and would like to overlay some GPS data which is in UTM83 Z18 coordinate system. I was reading in the MapInfo manual and also the MI mailing list archives about affine transformations and thought I would give it a try but doesn't seem to be working and was wondering if anyone might know what I'm doing wrong. These are the two control points that I'm using. GPS UTM83 Z18 AutoCad (local coords. metres) 1. X: 374408.5 3031.93 Y: 4986086.05 3033.78 2. X: 374701.6 3325.37 Y: 4986089.2 3054.71 Using Neil Moseley's Affine Calculator at http://members.iinet.net.au/~mose/prod03.html, which was very useful, the affine parameters were calculated and gave me the following results. A= 1.001811748958 B= -0.060642418938 C= -69686.58510395 D= 0.060642418938 E= 1.001811748958 F= -5014790.84331770 "My Grid Name", 300x Base Projection Clause, 1.001811748958, -0.060642418938, -69686.58510395, 0.060642418938, 1.001811748958, -5014790.84331770, Bounds Clause Using those parameters I created the following coordinate system at added this line to the "Universal Transverse Mercator (NAD 83)" section of the mapinfo.prj file "Affine transform to UTM83", 3008, 74, 7, -75, 0, 0.9996, 500000, 0, 7, 1.001811748958, -0.060642418938, -69686.58510395, 0.060642418938, 1.001811748958, -5014790.84331770, 0, 0, 10000000, 10000000 I then start up MapInfo and open the local survey table (non-earth) then through Map>Options change the projection to the new Affine transform projection I created. Then everthing just disappears and when I try to "view entire layer" still nothing shows up on the screen. Can anyone tell me what I'm doing wrong? TIA Dan _______________________________________________________________________ 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.
