Firstly I'm new to OpenDX but have spent quite a bit of time reading and
googling to see if there is an answer out there so please excuse me if
I'm asking an already answered question.
The data sets I'm working with are bathymetry sets which have been
exported from seismic processing systems. The data are ordered as (E =
easting, N = Northing):
E1 N1 depth (actually two way travel time)
E1 N2 depth
E1 N3 depth
.......................
E1 Nn depth
E2 N(1+ a) depth
E2 N(2 + a) depth
E2 N(3 + a) depth
.........................
E2 Nb depth
E3
etc. i.e the data is "gridded" but the bounding box is not a rectangle.
In the above a and b are integers indicating the offsets between
adjacent lines which result in a different number of samples for each
line. As the shape of the bounding box varies so these integers will vary.
Now to expose my ignorance ....
Using the general array importer I can successfully import these data as
"scattered". By using the connect module the software will determine the
connections and all is well, the data can be exported as a native dx
file and performance is great. The problem is the amount of time connect
uses. Running some timing tests it appears that he amount of time used
grows approximately as the square of the number of points. What this
means is that up to 500 000 points or so it is feasible to run connect,
after that the amount of cpu time becomes unacceptable. Given that the
data sets have 3 million plus points it would appear that I have two
options:
1) reduce the size of the data set - using the spreadsheet import this
seems easy enough during import but not so obvious using the General
Array Importer.
2) find a better way of describing the data. This type of data cannot be
unusual, is there a way of describing it in the General Array Importer?
If I defined a regular grid that uses exactly the same co-ordinates as
the data set, as a rectangle that covers the area, can the data points
be "mapped" onto the regular grid? Here I am assuming that by generating
a regular grid the connections would be created at the same time - is
this correct?
many thanks in advance for any help
Ted
--
----------------------------------------------------
Ted Bartlett
Terra Energy Services
Direct line: 00 27 (0)31 7671585
Mobile: 00 27 (0)73 4603100
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