grain2d grainSize vs area

[Ryann Rupp]

Hello,

I am hoping to get some clarification reading the grainSize property and area method summary for grain2d. My understanding for each value is the following: 

grainSize: the number of pixels per grain

area: the area of a grain which is equal to grainSize*step size* step size

When I use MTEX to calculate each of these values for a grain set, I do not find this relationship between the grainSize and area. For example for one of my scans with a step size of 2.0 um, I get the following results for a few different grains.

grainSize     area (MTEX)         grainSize*step size*step size      

40                174.9                     160

171              711.3                     684

8                  39.7                       32              

Can someone please tell me how the area is actually being calculated? My definition obviously does not match how the area is being calculated. The specimen is a single phase material and unindexed data makes up only 1-2% of the data. I have not be correcting the scans for unindexed points. Does grainSize and area include unindexed points that are encapsulated within a grain? Obviously this cannot be the difference between grainSize and area since my definition with an integer step size would never result in a decimal response. I am using MTEX 4.0.23.

I am going to go ahead and summarize my questions in a list. 

1. What are the definitions of grainSize and area for grain2d?

2. How is the area being calculated?

2. Does grainSize and area include unindexed points that are encapsulated within a grain? 

[Ralf Hielscher]

1. What are the definitions of grainSize and area for grain2d?

grainSize: the number of pixels per grain

area: the area of a grain

2. How is the area being calculated?

A grain is a polygon, the area of which is computed.

3. Does grainSize and area include unindexed points that are encapsulated within a grain? 

grainSize - no

area - yes

the point is the grainboundary can pass through pixels. Make a plot and magnify it :)

Ralf 

[ruediger Kilian]

Hi Ryan,
and just to add on Ralfs answer, whether holes are included or not depends on how your unindexed points are considered; if your unindexed pixels are of phase 'notIndexed' or just not known and empty and in the latter case how you calculate grains( using 'unitCell'). If you do not want to include holes in your measurement, make sure to consider 'notIndexed' or use 'unitCell' when calculating grains.
Cheers,
Rüdiger

[Ryann Rupp]

Thank you so much for both of your quick responses. Both of these responses were very helpful.