Ticket #200 (new task)

Opened 7 years ago

Last modified 7 years ago

Magnitude quality estimator is needed for localmag and TYPE_MAGNITUDE

Reported by: paulf Owned by: matteo
Priority: minor Milestone: All Platforms
Component: localmag Version: 7.6
Keywords: magnitude quality Cc:

Description

Fraco Mele in ticket #176 indicated that a quality estimator to judge how good the magnitude is would be a useful feature or localmag since the ML magnitudes can often be skewed when few stations are usable.

I am just continuing the discussion of this in this new ticket since the prior ticket was a localmag station filter algorithm implementation.

I believe ticket #176 should be closed now if all discussions there in were implemented...did anyone think about doing the Md distance filter? That is, use a the Md in the HYP2000ARC message as a distance estimator for how far to include stations in the ML computation.

Change History

comment:1 Changed 7 years ago by francomele

  • Keywords magnitude quality added

in wrML (lm_main.c @ 4724)

the following are defined and never used:

647	  MI.quality = 1.0;
648	  MI.mindist = -1.0;
649	  MI.azimuth = -1;

Also, the number of used channels is computed:

752	  MI.nchannels = nchan;

As a first attempt to define a magnitude quality in the range [0, 1], I would suggest :

{
    MI.quality = MI.nchannels /( MI.mag * MLQpar1);
    MI.quality > 1.0 ? 1.0 : MI.quality;
} 

where MI.mag is the magnitude and MI.nchannels is the number of channels that contributed to the ML computation.

MLQpar1 should be a parameter proportional to the density of the stations. For instance: for the Italian network MLQpar1 could be 10.

Other ML-quality estimators with values in the range [0, 1] could be easily combined to this one by multiplication.

We could also take into account for standard deviation, minimum station distance or (maximum - minimum) distance range, among the stations used in the ML computation.

Other suggestions would be greatly appreciated :-)

ciao,

franco

comment:2 Changed 7 years ago by quintiliani

Changes in revision r4773.

Moreover, it has been computed the minumun distance from location to station and put in the field mindist of message TYPE_MAGNITUDE.

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