Overview
The Synthetic Data Injector was created to allow Nimbus users to modify variables before Nimbus processing. This ensures that derived variables are computed with the updated information. The Synthetic Data Injector allows the user to modify the measured values with a function; it allows the user to modify variables with a constant value, and also to inject information from a user-created ASCII file. To denote data modification the data quality flag in Nimbus changes to "s" for synthetic data.

Using the Synthetic Data Injector
To use the Synthetic Data Injector, run Nimbus by typing nimbus from the command prompt. If you wish to modify a variable with a constant value or with a function, simply double click on the variable name and Nimbus' Edit Variable window will appear with synthetic data options.

Enter either a constant value for the variable or select a function you would like applied to the existing values in the variable. Press the "Apply" button, and then the "dismiss" button for the window to go away. All variables except derived variables can be modified with synthetic data during each Nimbus session. Derived Variables have other variable names listed under the calibration codes/dependencies column. Simply double click on the variables and make modifications in the edit-variable window. Please note that even if the Edit Variable window is opened for derived variables, the synthetic data options are not available. Please also note that, while you are able to modify all non-derived variables, you are advised not to modify the variables hour, minute, second, day, month, and year. Although Nimbus will run if these values are modified, if hour, minute and second are modified especially to a constant value you will only be able to see the modified value of time (hour:minute:second) in NCPLOT.

To inject synthetic data from a file the user should select the synthetic option from the file menu.

To create the synthetic data file the user can use any program that creates ASCII files; however each file created must follow the format specified below.

Below is an ASCII file that was created by n2asc. On the first line, the extra spaces between the variable names and after the last variable name were deleted.

  
TIME ADIFR BDIFR

  
12:42:18.000 1.000 2.000
  
12:42:18.040 1.000 2.000
  
12:42:18.080 1.000 2.000
  
12:42:18.120 1.000 2.000
  
12:42:18.160 1.000 2.000
  
12:42:18.200 1.000 2.000
  
12:42:18.240 1.000 2.000
  
12:42:18.280 1.000 2.000
  
12:42:18.320 1.000 2.000
  
12:42:18.360 1.000 2.000
  
12:42:18.400 1.000 2.000
  
12:42:18.440 1.000 2.000
  
12:42:18.480 1.000 2.000
  
12:42:18.520 1.000 2.000
  
12:42:18.560 1.000 2.000
  

Manual edits may be necessary to ensure that the user created ASCII file is organized appropriately. Modifications for some methods of ASCII file creation will be discussed in this document. The synthetic data file must be in the specified format or the Synthetic Data Injector will not work properly and in turn nimbus will not work properly.

Creating an ASCII file to work with the Synthetic Data Injector
Time must be the first data column in the file. It can be given a variety of names however it must be the first entry in the file, and it should be in the format hr:min:sec (or hr:min:sec:millisec for high-rate data). The first line of the file should contain time, followed by a single space, and names of the variables you wish to modify. Each variable name should be followed by a single space; however the last variable should be followed with a return to the next line. Each line after the first should contain a time stamp and a value of each of the variables listed in the first line. As the user you are not to leave any variable value blank on any lines, or the SDI will not work correctly, and you must include twenty-five milliseconds when running high-rate data or nimbus will exit and tell you that you didn't provide the SDI with 25 milliseconds worth of data.

You should not create a file with missing values like the file pictured below.

  
TIME ADIFR BDIFR

  
12:42:18.000 1.000 2.000
  
12:42:18.040 1.000 2.000
  
12:42:18.080       2.000
  
12:42:18.120 1.000 2.000
  
12:42:18.160 1.000 2.000
  
12:42:18.200 1.000  
  
12:42:18.240 1.000 2.000
  
12:42:18.280 1.000 2.000
  
12:42:18.320 1.000 2.000
  
12:42:18.360 1.000 2.000
  
12:42:18.400       2.000
  
12:42:18.440 1.000 2.000
  
12:42:18.480 1.000 2.000
  
12:42:18.520 1.000 2.000
  
12:42:18.560 1.000 2.000
  

If you choose to create an ASCII file with n2asc, after creating the file, open the newly-created ASCII file in a text editor and remove all extraneous spaces in between the variable names, leaving only one space, and delete all the spaces after the last variable name on the first line. Save the modified file and you are ready to inject synthetic data.

If you choose to create an ASCII file with Microsoft excel, enter the desired variable names, time-stamps, and values in the spreadsheet. When you save the file, select save as type Text(MS_DOS) and save the file. Assure Microsoft excel that you want to save in that format by clicking OK and then yes. Close the Excel file, and tell excel you don't want to save the changes you've made to the file. Next open the text file in a text editor. Replace the tab between each of the variable names with a single space. Save the file and you're ready to inject synthetic data.