Document MT0605P.E
© Xsens Technologies B.V.
MTi User Manual
20
These are the same filter profiles as the MTi 10-series, but they are differently tuned in the MTi 100-
series to make better use of the gyroscopes and calibration. For descriptions on these filter profiles,
refer to section 3.2.4.
3.3.6
MTi-G-700 filter profiles
The MTi-G-700 GPS/INS uses different filter profiles as it is typically used in outdoor applications.
These filter profiles are described below. Please note the specific cautions with each of these filter
profiles.
Nr
Name
IMU
Magnetic
field
Barometric
pressure
GPS
Holonomic
constraints
Product
1
General
•
•
•
700-GPS/INS
2
GeneralNoBaro
•
•
700-GPS/INS
3
GeneralMag
•
•
•
•
700-GPS/INS
4
Automotive
•
•
•
•
700-GPS/INS
5
Automotive
UrbanCanyon
•
•
•
•
700-GPS/INS
The
General
filter profile is the default setting. It makes few assumptions about movements. Yaw is
referenced by comparing GPS acceleration with the on-board accelerometers, so the more movement
(when GPS is available) will result in a better yaw. Altitude (height) is determined by combining static
pressure, GPS altitude and accelerometers. The barometric baseline is referenced by GPS, so during
GPS outages, accurate height measurements are maintained because this barometric baseline is
monitored.
The
GeneralNoBaro
filter profile is very similar to the general filter profile. However, it does not use
the barometer for height estimation (it thus uses GPS and accelerometers only). Since airflows near
the venting holes in the MTi-G will lower the barometric pressure (and thus make height estimations
inaccurate), you can use this filter profile when the MTi-G is mounted in such airflow.
The
GeneralMag
filter profile bases it yaw mainly on magnetic heading, together with comparison of
GPS acceleration and the accelerometers. Although this combination makes the yaw more robust than
magnetic field alone, a homogenous or calibrated-for magnetic field is essential for good-performance
yaw. Other parameters are tuned the same as in the General filter profile.
The
Automotive
filter profile assumes that the yaw of the MTi-G is also the GPS course over ground
(holonomic constraints). This assumption holds for most automotive/ground vehicles, except for those
who experience side slip, such as racing cars, tracked vehicles, some articulated vehicles (depending
on where the MTi-G is mounted) and vehicles driving on rough terrain. The Automotive filter profile
thus uses GPS to determine the yaw. Note that it is essential to mount MTi-G exactly in the direction of
movement in order to prevent an offset. Please refer to 4.2.3 for proper mounting. When GPS is lost,
yaw will be determined by the velocity estimation algorithm for 60 seconds, before yaw is determined
by gyroscopes integration only. Should GPS outages recur regularly or if you have bad GPS-
availability (e.g. in urban canyons), consider using AutomotiveUrbanCanyon.
In the Automotive filter profile, yaw is locked (e.g. gyro bias will be estimated and yaw will not change),
when GPS indicates that there is no movement. This is useful when standing still, as gyro bias would
otherwise induce a yaw drift.
