On 12/2/2014 2:56 PM, Basques, Bob (CI-StPaul) wrote:
All,
I have a bunch of individual LINE segments in Postgres and want to
display them via MapServer like so:
First:
·Get a chunk of them based on a set of IDs (a set of three for example)
and a begin/end timestamp (got this figured out already)
·Take the result and combine up the separate line strings into
multi-segment (grouped) lines ordered by ID, timestamp (got this figured
out for individual IDs)
·Add a random number to each grouping of multi-line string rows for
dynamic color-coding of each group. (got this figured out for individual
IDs)
·Have results output as three rows, one for each multi-segment line.
If the goal is to just display them, then you do not need to create a
multi-segment line, just display them as individual lines with the color
attribute.
I you need them 'glued together' as a multilines for some other reason.
then union should work.
select color, union(geom) from lines group by color order by timestamp;
I’m lost on the method to do the last piece. Mostly it relates about
how to approach which piece first. Seems like a straightforward SQL,
but I’ve tried a few different things, and it falls part each time for me.
Anyone have examples of something like this to start from?
The pertinent Mapfile fragment, I know this only color codes each
individual segment at the moment. VEH_IDs are passed into the MapFile
from CGI (vname=veh_id in DB):
DATA "the_line FROM (select the_line, vname, acqtime, trunc(random() * 4
+ 1) rnum from loc) as foo USING unique vname using SRID=4326"
FILTER " vname in (%veh_id%) AND acqtime >
'%time_idx1%' AND acqtime <'%time_idx2%' "
VALIDATION
'time_idx1' '.*'
'time_idx2' '.*'
'veh_id' '.*' ## veh_id=’100’,’200’,’300’ . . .
END
CLASSITEM "rnum"
CLASS ## Use the RNUM value to color code the line
strings randomly.
STYLE
COLOR 255 0 0
WIDTH 5
END
EXPRESSION '1'
END
CLASS
STYLE
COLOR 0 255 0
WIDTH 5
END
EXPRESSION '2'
END
CLASS
STYLE
COLOR 0 0 255
WIDTH 5
END
EXPRESSION '3'
END
CLASS
STYLE
COLOR 255 255 0
WIDTH 5
END
EXPRESSION '4'
END
CLASS
NAME "Segments"
STYLE
COLOR 0 255 0
WIDTH 5
END
END
Thanks
Bobb
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