[GRASS-user] i.maxlik's reject versus i.segment's goodness

[Markus Metz]

On Wed, Nov 19, 2014 at 2:04 PM, Moritz Lennert
<mlennert at club.worldonline.be> wrote:
> On 18/11/14 09:47, Markus Metz wrote:
>>
>> On Sun, Nov 16, 2014 at 3:21 AM, Vaclav Petras <wenzeslaus at gmail.com>
>> wrote:
>>>
>>> Hi,
>>>
>>> I executed the examples in i.cluster and i.maxlik manuals and also the
>>> following i.segment command:
>>>
>>> i.segment group=lsat7_2002 at w1-imagery output=lsat7_2002_segments
>>> threshold=0.5 goodness=lsat7_2002_segments_goodness
>>>
>>> (using the imagery group created in i.cluster example, otherwise
>>> unrelated)
>>>
>>> I looked at goodness from i.segment and then reject from i.maxlik. I
>>> noticed
>>> that there is some correlation between these two. Well, this is quite
>>> okay
>>> since they are using same pixel values. However, then I noticed that low
>>> values of goodness (-5000, ...)
>>
>>
>> i.segment's goodness estimate is supposed to be in the range [0,1].
>> Fixed in r62793,4. Can you test again?
>
>
> Could you explain / put into the manual the explanation of the calculation /
> meaning of this goodness of fit ?

Done in r62830:

The goodness of fit for each pixel is calculated as 1 - distance
of the pixel to the object it belongs to. The distance is calculated
with the selected similarity method. A value of 1 means
identical values, perfect fit, and a value of 0 means maximum possible
distance, worst possible fit.

Markus M