ArcMap Field Calculations

Often in a feature class, you will have an attribute which stores the file name and path of a file that is linked to that feature. For example, you may have a photo, a video or a condition report (PDF) which contains additional information about the feature. You can then use the Hyperlinking functionality in ArcMap to view the files via your map.

If you are storing the file paths as full paths (as opposed to relative), you may encounter some problems if you want to move the location of the images, reports etc. You could manually go through and update the paths, or you can use these simple field calculations.

Change File Paths
FileField = [FILE_PATH]
OrigPath = "D:\Temp"
NewPath = "C:\temp"
output = Replace( FileField , OrigPath, NewPath )

Remove File Path
FileField = [FILE_PATH]
iLength = Len ( FileField )
iLastInd = InStrRev ( FileField , "\" )
iDif = iLength - iLastInd
output = Right ( FileField , iDif )

To use them:

1. Open the table of the feature class in ArcMap
2. Start an edit session
   
3. Right click on the column header, and select Field Calculator
4. Click the advanced check box
5. Copy the script into the "Pre-Logic VBA Script Code" box
   
6. Replace the FileField property to the field that contains the file path in your feature class (delete the [FILE_PATH] part, and double click the appropriate field in the Fields List of the calculator)
7. If changing the file path, update the OrigPath and NewPath variables
8. Type output into the bottom box
9. Click ok
10. Save your edits
    

Increasing the length of a text field in a File Geodatabase

I was recently working on a job where I needed to increase the length of a text field of a feature class in a File Geodatabase. Similarly to changing the type of a field, this was not as straightforward as you might think. The process I went through was:

1. Create a temporary field to store the values of existing features
2. Delete the original field
3. Create a new field, with the increased length (using the same name as the original)
4. Copy the values from the temp field into this new field
5. Delete the temp field

So basically, a lot of work to make a very minor change. I ended up using Model Builder and writing a Python script to automate the process. Being the nice people that we are, we uploaded it to ArcScripts so anyone can download it.

If you are interested, you can download the script here.

Interested in finding out more about Model Builder? Stay tuned, RIA is currently in the process of developing an Introduction to Model Builder training course.