| Re: tracking clusters through multiple timesteps [message #79351 is a reply to message #79254] |
Mon, 20 February 2012 10:20  |
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Ian[1]
Messages: 4
Registered: February 2011
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Junior Member |
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Haha, thanks for such a quick reply David - i really wish i could go
fishing instead, but unfortunately this ugly problem needs dealing
with first :( The time resolution is very high - 15 minutes - so there
is a huge degree of overlap between blob at t and blob at t+1.
For now i would like to work on an idealised case with no splitting or
merging - but where the cloud will move quite a way from its start to
finish location. I should specify that i am very much an IDL novice
but it seems logical to pass the index given to a cluster of pixels
(above a threshold of, say, 250, to filter out noise resulting from
the initial flagging stage) at t to an overlapping cluster at t+1.
So if i just deal with the first cluster at t first of all, using the
histogram tip i picked up from you...(fld1 and fld2 are two successive
timesteps of flag data from my much larger parent dataset
(intarr(1133,751)))
;find blobs at t
blobs1=label_region(fld1)
pop1=histogram(blobs1)
x1=where(pop1 ge 250)
a=where(blobs1=x1[1])
;select first cluster only, ignore the rest
cluster1=intarr(1133,751)
cluster1(a)=1
;find blobs at t+1
blobs2=label_region(fld2)
;-set all blobs that pass size threshold equal to 1 so that overlap
can be found with cluster1
pop2=histogram(blobs2)
x2=where(pop2 ge 250)
tmp=intarr(1133,751)
for i=0,n_elements(x2)-2 do begin
j=where(blobs2 eq x2[i+1])
tmp(j)=1
endfor
;add cluster1 to tmp to work out overlap (overlapping regions have
value 2)
overlap=cluster1+tmp
;assign cluster at t+1 to which this overlapping region belongs the
same identifier as the cluster at t
errr, here i get stuck!
Ian
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