English

How To: Convert a file with coordinates in degrees, minutes and seconds to a shapefile in ArcMap 9.x

Summary

 

Note:
The procedure below is for ArcGIS 9.3.1 or earlier versions. Starting at ArcGIS 10.0, expressions in the Calculator are created using only VBScript or a standard Python format.  For the equivalent process in ArcGIS Desktop 10, refer to Esri Knowledge Base article 37264.

Procedure

Follow the steps below.

  1. Format the coordinate values for ArcGIS to correctly interpret the data.
  1. Coordinates in DMS from a file need to be formatted with spaces separating the degree, minute and second values, as shown in the following example:
    80 37 40,35 00 48
     
  2. For data in North America, the longitude values must be negative. Note the following example:

    -80 37 40,35 00 48
     
  3. Each column in the table must have a heading that describes the data entered into that column of the table:

    Longitude,Latitude
    -80 37 40,35 00 48
     
  4. The table must have a field that contains a unique identifying number for each record in the table (primary key).

    ID,Longitude,Latitude
    1,-80 37 59,35 00 38
  1. Start ArcMap with a new, empty map once the table is correctly formatted.
  2. Save the script below as 'conv_DMS2DD.cal' in ArcMap with the following steps:
    Code:
    Dim sField
    Dim sDMS As String, sS As String, sSuf As String, sPre as string
    Dim sList
    Dim i As Integer, j As Integer
    Dim iDec As Integer, iNum As Integer
    Dim dD As Double, dM As Double, dS As Double, dDD As Double
    Dim bReplace As Boolean
    '=============================
    'Change the source field name bellow
    sField = [dms]
    '=============================
    sDMS = sField
    If Len(Trim(sDMS)) = 0 Then
      dDD = 0
    Else
      iDec = 0
      iNum = 0
      For i = 1 To Len(sDMS)
        sS = Mid(sDMS, i, 1)
        If Not IsNumeric(sS) Then
          If sS = "." Then
            If Not iDec = 0 Then
              bReplace = True
            Else
              bReplace = False
            End If
            iDec = iDec + 1
          ElseIf sS = "-" Then
    	sPre = "-"
            bReplace = True
          Else
            bReplace = True
          End If
          If bReplace Then
            If iNum > 0 Then
              Mid(sDMS, i, 1) = ","
            Else
              Mid(sDMS, i, 1) = " "
            End If
          End If
        Else
          iNum = iNum + 1
        End If
      Next i
      sList = Split(sDMS, ",")
      Dim iLen As Integer
      If UBound(sList) = 0 Then
        sDMS = sList(0)
        iLen = Len(sDMS)
        If iLen >= 4 Then
          dS = CDbl(Mid(sDMS, iLen - 1, 2))
          dM = CDbl(Mid(sDMS, iLen - 3, 2))
          sDMS = Left(sDMS, (iLen - 4))
          If (Len(sDMS) > 2) Then
            dD = CDbl(Right(sDMS, 3))
          ElseIf (Len(sDMS) = 0) Then
            dD = 0#
          Else
            dD = CDbl(sDMS)
          End If
        Else
          dDD = 0
        End If
        dDD = dD + dM / 60# + dS / 3600#
      Else
        j = 0
        dD = 0#
        dM = 0#
        dS = 0#
        For i = 0 To UBound(sList)
          If IsNumeric(sList(i)) Then
            If j = 0 Then
              dD = CDbl(sList(i))
              j = j + 1
            ElseIf j = 1 Then
              dM = CDbl(sList(i))
              j = j + 1
            ElseIf j = 2 Then
              dS = CDbl(sList(i))
              j = j + 1
            End If
          End If
        Next i
        dDD = dD + dM / 60# + dS / 3600#
      End If
      If dDD < -180# Or dDD > 180# Then
        dDD = 0#
      End If
      If sPre = "-" Then  
        dDD = dDD * -1#
      End If
    End If
  1. Open a table in ArcMap.
  2. Right-click a field and select Calculate Values.
  3. Check the Advanced check box.
  4. Copy the code above into the Pre-Logic VBA Script Code section of the Field Calculator.
  5. Type dDD into the bottom section of the Field Calculator.
  6. Click Save to save the script to a .cal file and name the file 'conv_DMS2DD.cal'.
  1. Follow these steps to run the code above in the Field Calculator:
    1. Add the table containing the DMS coordinates to ArcMap through the Add Data button.
    2. Right-click on the table name > Data > Export and export the table to a DBF file.
    3. Open the DBF table and add items named 'longDD' and 'latDD' to the table, defining these as Double, Precision 18, and Scale 13.
    4. Calculate the field values for 'longDD' and 'latDD' by starting a load of the conv_DMS2DD.cal script to the Field Calculator.
       
      Note:
      Change the name of the field in the script to that of the original DMS fields:
      
      'Change the source field name below
      sField = [Long]
  2. Right-click the DBF table and select Display XY Data after the coordinates have been converted from DMS to DD.

    Define the projection for the event layer by clicking the Edit button in the Spatial Reference of Input Coordinates section of the dialog box.
    Note:
    Defining the projection permits the data to display in the correct location in ArcMap as an Event layer.
  3. Convert the Event layer to a shapefile.
    1. Right-click the Event layer and select Data > Export data.
    2. Select the output location for the shapefile and type in the name.
    3. Click Save and OK in the Export Data dialog box to create the shapefile.

Related Information