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
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