Parent Command
all second-level commands in block > OBSERVATION requiring element names.

Subcommand
all fourth-level commands in block > OBSERVATION

Description
This command reads one or more element names. Most observation types refer to a variable that is associated with a grid block (as opposed to a connection or sink/source name). Element names are designated by a three-character/two-integer (FORTRAN format: AAAII) code name. Blanks in the element names as printed in the TOUGH2 output file must be replaced by underscores (e.g. an element name specified in the TOUGH2 input file as 'B 007' is printed as 'B 0 7' in the TOUGH2 output file. Therefore, it must be addressed in the iTOUGH2 input file as 'B_0_7'). Multiple elements can be specified, and iTOUGH2 calculates the sum or mean of the corresponding output variable (see subcommands >>>> SUM and >>>> MEAN, respectively). A sequence of iplus elements can be generated by increasing the number found in substring [islotb-islote] (default: [4-last]) of the last element. The following two command lines are identical:

>>> ELEMENT: AA__1 BB_15 +3 [4-5]
>>> ELEMENT: AA__1 BB_15 BB_16 BB_17 BB_18

If keyword COORDINATES is present, coordinates can be specified, and the element closest to these coordinates will be identified. If keywords COORDINATE BOX or COORDINATE RANGE are present, all elements within the specified box will be included in the element list. Element coordinates must be present in columns 51–80 of the TOUGH2 ELEME block.

If keyword PROFILE, CROSS-SECTION, or MAP is present, the data (which must be provided in an external file, see command >>>> DATA FILE: filename) are organized spatially by lists of coordinates followed by columns of measured values for each survey time. The data will be assigned to the nearest element (element coordinates must be present in columns 51–80 of the TOUGH2 ELEME block.). Keyword PROFILE supports one-dimensionl, vertical data profiles (i.e., Z-coordinates), whereas CROSS-SECTION and MAP both require X-, Y-, and Z-coordinates. Profile data are given as follows:

NZ NT
XCoord YCoord
Time(1) Time(2) ... Time(NT)
Z(1) Data(1,1) Data(1,2) ... Data(1,NT)
Z(2) Data(2,1) Data(2,2) ... Data(2,NT)
... ... ... ... ...
Z(NZ) Data(NZ,1) Data(NZ,2) ... Data(NZ,NT)

Two- or three-dimensional data are given as follows:

NP NT
Time(1) Time(2) ... Time(NT)
X(1) Y(1) Z(1) Data(1,1) Data(1,2) ... Data(1,NT)
X(2) Y(2) Z(2) Data(2,1) Data(2,2) ... Data(2,NT)
... ... ... ... ... ... ...
X(NP) Y(NP) Z(NP) Data(NP,1) Data(NP,2) ... Data(NP,NT)

Example
> OBSERVATION
>> GAS SATURATION
>>> ELEMENTS: ELM_0 + 99
>>>> ANNOTATION : Mean saturation
>>>> take the MEAN of the saturation in all 100 elements
>>>> DATA on FILE : Sg.dat
>>>> DEVIATION : 0.05
<<<<
<<<

>> CAPILLARY pressure
>>> ELEMENT COORDINATE RANGE: 10. 0.4 -1.0 40.0 0.5 -5.0
>>>> ANNOTATION : Mean Pcap
>>>> take the VOLUMEtric MEAN of all elements in box
>>>> DATA on FILE : Pc.dat
>>>> DEVIATION : 1.0E4
<<<<
<<<
<<

See Also
>>> CONNECTION | >>> SINK | >>>> MEAN | >>>> SUM