Discrete samples
Discrete Sample tables, and the functions which process data contained in those tables, are designed for storing data for sample points where there is no direct relationship between sample points. There are two variants of the Discrete Sample table.
The first is the time independent variant. This type of table has the fields samp_id, y, x, z and user defined optional fields and it is ideally suited for storing data which is typically collected for geochemical soil sampling programs.
The second type is the time dependent variant. This type of table has the fields samp_id, samp_date, y, x, z and user defined optional fields. This type of table is ideally suited for recording changes in sample value at the same sample point over time. This is possible since the unique identifier for each row stored in the table is created from the samp_id and samp_date fields. It is even possible to record changes in location for the sample points since the x, y, and z fields are recorded explicitly for each sample measurement. This makes the time dependent variant of the discrete sample table ideally suited to storing of slope stability monitoring points. One of the functions available, moving discrete samples, is designed specifically for processing this type of data.
Discrete Samples vs Time
This function will only work on time dependent discrete sample tables. This function will create a string file which contains one string for each sample. Each string represents a Sample Value Vs Time graph which is suitable for viewing in the GRAPHICS module or plotting using the PLOTTING module. This function is useful when the value of a sample field must be analyzed with respect to time.
To run this function: Choose Database > Extract > Discrete samples vs time, or...
Define the string file to be created
Enter the Location to define the string file which will be created by this function.
Define the time units and time datum for output
The string file which is created has the sample value stored in the Y field and the samp_date field of the sample in the X field. Since the X field of the string file can only be used to store numeric data it is necessary to convert the value in the samp_date field, normally expressed in the form yyy-mm-dd hh:mm:ss, to a purely numeric form in the time units of choice.
You can set Time units to Seconds, Minutes, Hours or Days.
Datum
In addition to defining the units for storing the samp_date in the X field of the string file, you must also define the time datum from which all date values are referenced. This time datum is subtracted from all sample dates to give values which are more manageable in the string file. The value entered into this field must be of the form yyyy-mm-dd hh:mm:ss. Note that if trailing fields are omitted then they are assumed to be zero, for example, "1990-01-01" is equivalent to "1990-01-01 00:00:0"
Define the discrete sample table to be processed
Enter the name of the time dependent discrete sample Table which is to be processed.
Table
Display only. This is the name of the table which is being processed.
Field Name
Enter the names of up to 10 fields from which values are to be extracted and stored in the string file which is created by this function. All field names entered must be numeric fields.
Choose Apply to display the SELECT CONSTRAINTS FOR FIELDS form. Enter any query constraints required on this form and choose Apply to complete the function.
One string is created in the resultant string file for each sample ID in the sample table. The values from the first named sample field are written to the Y field of the string file. The X field of the string file contains the value from the samp_date field expressed in terms of the time units specified from the datum time entered earlier. The Z field is the elevation of the point from the database. The description fields contain the following:
Below is a brief example of the type of data which is written to the string file which is created.