Chemistry File FormatNote: If you are not a licensed user, you may build data files, but you will not be able to utilize them in EVS or MVS because the files you create will not be password protected (allowing them to be used in a demo version). Instead, we recommend that you review Loading Existing EVS Geology or Chemistry Files or&ldots;.
If you are a demo user, be sure to CHECK "Run in Demo Mode" before Launching Applications. The demo version will not allow you to analyze or visualize data files created with the extension because they are not password protected. When "Run in Demo Mode" is checked, the default data files for each application (ones with passwords) will be used.
CREATING A CHEMISTRY FILE:
The following section will show you how to build an EVS chemistry file (.csv) with ArcGIS.
To see the format for a CSV file click here: Chemistry File Format
Now that the extension is loaded, click on the "Create EVS Data File" button to reveal:
Choose Create Chemistry File and this initial window will open:
From this menu, you select the layers and features from which you want to extract chemistry data. You can also choose whether to include all features of a layer or only the selected features. Let’s accept the current setting of the borings layer and all features. Hit Next to proceed and the following window will appear.
At this point, you specify the fields of your data source that will be used to create a chemistry file. If your fields are named reasonably, the process of specifying the fields can be very simple because the extension does so much for you automatically. In the example above, the fields of our data source that correspond to x and y coordinates by default are assigned to the x & y coordinates of the points in the shapefile. However, if you wish to use x and/or y coordinates (or Northings or Eastings) from the associated tables, you may do so.
The remaining fields will be automatically filled in according to some rather straightforward rules. In the discussion of these rules, all field names are case insensitive and an asterisk "*" refers to one or more wildcard characters.
The Z coordinate will use the LAST field with any of the following names: "Z*", "elev*", or "depth*".
Top (used to designate the ground surface) will use the LAST field with any of the following names: "top*", "ground*", or "grnd*".
Boring will use the LAST field with any of the following names: "bor*" or "well*".
Finally, the Data components or analytes will automatically select all remaining fields except that all of the following names will be ignored: "id*", "objectid*", "oid*", "fid*", "key*", "pr*key", "<Measure from Point>", "bot*", "sym*", "X*", "east*", "Y*", and "north*".
Just because a field is automatically selected (or not selected) does not imply that you cannot change these choices. You should always review the automatic selections to see that they make sense for your project. However, the wizard will usually save a great deal of time and if you choose your field names (e.g. field naming during the creation of queries).
In this example our Boring_ID is "Bore", the Ground Surface is Top, Z Coordinates are Z and they represent true elevations (as opposed to depths below ground surface).
Note that in this example, only one field represents chemistry data, but the extension allows you to specify multiple fields for multiple chemicals or timesteps. Selection (or deselection) is done Left Mouse Button.
There are two other very important fields in this window that should be carefully considered. They are the Preprocessing Clip Min and Postprocessing Clip Min. These fields control the clipping parameters for pre and post processing in all of the EVS modules that use read chemistry (.csv) files. The affected modules are Krig_3D, Krig_2D, Krig_Fence, post_samples, and Stat_CSV_GEO.
The three kriging modules use the Preprocessing Clip Min values as the value to assign to non-detects or any value less than the clipping value. C Tech recommends that:
Preprocessing Clip Min value should be set to a fraction of the detection limit for the selected analyte (chemicals or parameters).
When using "Log processing" the fraction should normally be one-tenth, but may be as high as one-half of the detection limit.
If all of the analytes for a site do not have the same detection limit it is best to krige them separately, using appropriate (fraction of detection limit) clipping values for each.
If all of the samples for any analyte do not have the same detection limit it is best to assign numeric values to your non-detects (fraction of detection limit) values for each non-detect value.
If you have already assigned numeric values to your non-detects be sure to set the Pre Clip Min value less than your lowest assigned value to prevent modifying your assigned values.
All five modules use the Postprocessing Clip Min values as the value to assign the final minimum values used in the output field (visualization). C Tech recommends that:
Postprocessing Clip Min value should be set to the actual (nominal) detection limit for the analyte. By doing this, you avoid having a model where any values are less than the detection limit. A lower value would not be defensible since your measurement techniques would be unable to verify the lower value.
If all of the analytes for a site do not have the same detection limit it is best to krige them separately, using appropriate detection limit clipping values for each. If you wish to have multiple analytes in the same field, they can be combined later using the combine_comp module. [This note only applies to the kriging modules.]
When you hit Finish it will give you a file browser and allow you to name and specify the folder for your chemistry file. When you hit Finish, the file browser will appear. Save the file in the ctech\data folder as evs-test.geo:
Note: If you do not add the .csv suffix, it will do it for you.
If you are a licensed user, you can jump directly to Launch Applications or review the next topic which covers Loading Existing EVS Geology or Chemistry Files.