User manual


 DocumentMT0100P.N
©XsensTechnologiesB.V. MTiandMTxUserManualandTechnicalDocumentation
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2. AheadingresetthatredefinestheX‐axisoftheglobalcoordinateframewhilemaintainingtheZ‐axis
along the vertical (also known as “boresighting”). After the heading reset the orientation will be
expressedwithrespecttothenewglobal(earthfixed)referenceframe.
3. Anobjectresetthatdefineshowthesensorisorientedwithrespecttothecoordinateaxestowhichit
isattached.Aftertheobjectreset,boththeorientationandthecalibratedsensordataareexpressed
withrespecttotheaxesoftheobject.
4. Acombinedobject/headingreset,referredtoasalignment.

NOTE:Forallco‐ordinatesystemresetfunctionsitisimportanttorememberthatthehousingoftheMTxcan
not be considered an accurate reference. Placement and subsequent aligning must be done very carefully
otherwise(alignment)errorsmaybeinduced.

4.6.2 Arbitraryalignment
If the measured kinematics is required in an  object coordinate system (O) with a known orientation with
respecttostandardsensorcoordinateframe(S),theobjectalignmentmatrixcanalsobesetwithanarbitrary
but known orientation. This can be useful if for mechanical reasons the MTi / MTx can only be fastened in
some specific orientation. The MTi and MTx Low‐level communication protocol describes the message
SetObjectAlignmentthatisrequiredtosetthematrix.

Theobjectalignmentmatrix(R
OS
)isappliedtotheoutputdata(R
GS
)accordingtothefollowingequations.For
3Dorientationdata,

 
()
T
RRR=
R=
S
ss
001
⎡⎤
GO GS OS

andforinertialandmagneticdata.

OSO


Example
Theobjectalignmentmatrixisgivenby

010
100
OS
R
⎢⎥
=
⎢⎥
⎢⎥
−
⎣⎦


Here O represents the object coordinate system and S the standard sensor coordinate system described in
section2.1.1.OncetheobjectalignmentmatrixissettoR
OS
,thesensoroutputwillbeexpressedwithrespect
totheobjectcoordinatesystemdrawninfollowingfigure(b).
(a)   (b) 

TheMTiwiththesensorcoordinateframe(a)andtheobjectcoordinateframe(b).