Handling referenced data channels

[Alexander Gerhard]

Dear colleagues,

I would like to handle the correct setting of data, names/codes and parameters to write test channel files where the channels are referenced. The source of the raw data is video analysis.

1. channel = displacement-x within a reference system = vehicle:
main location = HEAD, channel code = 00HEAD000000DSXV
channel file/descriptor "Reference system" = "moving vehicle, alignment to vehicle at T0" (example string)
OK?

2. same as (1) but referenced to the (static) displacement value at T(ref),
calculation before storage of the channel = x’(t) = x(t) – x(Tref):
a constant offset is subtracted from the channel vector,
Is there any descriptor or possibility to indicate this type of pre-calculation in MME 1.5 or 2.0?
Is there any descriptor to enter the (subtracted) offset?
(Please note: this can be necessary not only for displacement but also e.g. for velocity.)

3. same as (1) but referenced to the dynamic displacement of another "point":
calculation before storage of the channel = x’(t) = x(t) – xref(t):
a time-variant offset is subtracted from the channel vector,
Is there any descriptor or possibility to indicate this type of pre-calculation in MME 1.5 or 2.0?
Is there any descriptor to enter the source name/code or values of the reference?

Do you recommend to handle it in the MME-2.0 file *.rsi by giving comments to "General description of the reference
coordinate system"?
The .ref files handle the transformation of 3D coordinate systems and are a bit to complex for the requested needs, are they?

Looking forward to your comments!
Alexander Gerhard

[derpmann]

Dear Dr. Gerhard,
you want to handle 3 variations of data from the same origin.
1) absolute values in a specific reference coordinate system (e.g. vehicle): x(t)
2) values relative to a specific time reference tref of the same channel x'(t) = x(t) - x(tref)
3) values relative to a another channel xref x'(t) = x(t) - xref(t)

For MME 1.x the measurement values should be balanced.
This is reasonable for data from electrical transducers.
For data from filmanalysis I prefer to exchange absolute values (option 1).
If this is not possible or meaningfull we have to exchange relative data.
In MME 1.x it is not possible to distinct between the different options by using FineLocations or Dimensions.
For using more than one option at the same time you have to increment one of the FineLocations
(e.g. 00HEAD0000H3DSXV, 00HEAD0100H3DSXV, ...).
You should use the first FineLocation which has the value "00".
Within the header section of the channel files I recommend to use the descriptors
"Reference system" and "Data source" (e.g.):
1)

Code: Select all

Reference System            :vehicle
Data source                 :camera

2)

Code: Select all

Reference System            :vehicle@tref
Data source                 :calculation

3)

Code: Select all

Reference System            :xref
Data source                 :calculation

For MME 2.0 I recommend the use of different reference coordinate systems.
The 3 reference systems of the examples should be used as "Reference system id"
within the channel data files, the reference system information (.rsi) and
reference system data file (.res).
The usage of different file extensions for the different reference systems makes it possible
to use the same channel code for all options.

Best regards
Peter Derpmann-Hagenstroem