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Technical Article   HowTo:  Convert a file with coordinates in degrees, minutes and seconds to a shapefile using ArcMap

Article ID: 27548
Software:  ArcGIS - ArcEditor 9.2, 9.3, 9.3.1 ArcGIS - ArcInfo 9.2, 9.3, 9.3.1 ArcGIS - ArcView 9.2, 9.3, 9.3.1
Platforms: N/A

Summary


 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 -show me-
Summary
Instructions provided describe the process for converting point data in degrees, minutes and seconds (DMS) to a shapefile using a Python script in ArcMap.

 The instructions in this article apply only to ArcGIS Desktop version 10 and later versions. For the equivalent process in earlier versions, refer to ESRI Knowledge Base article 27548.
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Procedure
  1. Format the coordinate values so ArcMap can correctly read the data.

    A. 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:
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    B. For data in North America, the Longitude values must be negative. Note the sample:
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    C. Each column in the table must have a heading that describes the data entered into that column of the table.
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     Any field name can be used, but the name must not be over ten characters long and must not contain spaces or special characters.

    D. The table requires a field that contains a unique identifying number for each record in the table.
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  2. When the table is correctly formatted, start ArcMap with a new, empty map. Use the 'Add Data' button to add the table to ArcMap. To ensure that the table can be edited in ArcMap, do the following:

    A. Right-click on the table name > Export to DBF. This creates a table that can be edited in ArcMap.
    B. Add the new DBF table to ArcMap.
  3. Right-click on the new DBF table name and select Open.

    In the Table dialog box, click on the Table Options button and select Add Field.

    Add a new field named 'LongDD' to the table, defining the field as Type: Double. Accept the default values for Precision and Scale.

    Add a second new field named 'LatDD' to the table, also defined as Type: Double.

    These new fields contain the Longitude (X) and Latitude (Y) coordinates in decimal degrees.
  4. Copy the following Python script into NotePad or another text editor. In the NotePad 'Save As' dialog box, change Encoding: value to 'Unicode'. Name the file "conv_DMS2DD.cal". Click 'Save'.
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  5. In ArcMap, follow the steps below to execute the script and convert the DMS values to DD:

    A. Start an Edit session.
    B. Open the new DBF table, right-click on the field name LongDD and select Field Calculator.
    C. At the top of the Field Calculator dialog box, select the Python radio button.
    D. Click Load, navigate to the location where conv_DMS2DD.cal is saved on the computer, and click Open.
    E. In the lower window, where the string appears that reads 'Convert("ChangeFieldNameHere")', double-click between the parentheses to select the string.
    F. In the Fields box, double-click on the name of the field that contains the Longitude value in DMS. The field name is copied into the lower window between the parentheses.
    G. Click OK. The decimal degree values for Longitude are calculated into the LongDD field.

    Repeat Steps B through G, this time selecting the LatDD field and entering the original Latitude field name.

    Save Edits and stop editing.
  6. Right-click on the name of the DBF table and select Display XY Data.
  7. In the Display XY Data dialog box, select LongDD as the X field and LatDD as the Y field.
  8. Click on the Edit button and select the correct Geographic Coordinate System definition for the coordinates. For assistance in finding the correct definition, refer to Knowledge Base article 29280, entitled "What geographic coordinate system or datum should be used for my data?", from the link in the Related Information section below.
  9. Apply the projection definition to the data. An Events theme will be added to ArcMap that displays the points from the table.
  10. Right-click on the Events theme, select Data > Export data, and export the Events theme to a shapefile or geodatabase feature class.

    After the data is exported to a shapefile or geodatabase feature class, there is an option to add the newly exported data to the map as a layer.

Instructions provided describe the process for converting point data in degrees, minutes and seconds (DMS) to a shapefile using ArcMap.

Procedure

Follow the steps below.

  1. Format the coordinate values for ArcGIS to correctly interpret the data.

    A. 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

    B. For data in North America, the longitude values must be negative. Note the following example:

    -80 37 40,35 00 48

    C. 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

    D. 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

  2. Start ArcMap with a new, empty map once the table is correctly formatted.
  3. Save the script below as 'conv_DMS2DD.cal' in ArcMap with the following steps.

    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

    A. Open a table in ArcMap.

    B. Right-click a field and select Calculate Values.

    C. Check the Advanced check box.

    D. Copy the code above into the Pre-Logic VBA Script Code section of the Field Calculator.

    E. Type dDD into the bottom section of the Field Calculator.

    F. Click Save to save the script to a .cal file and name the file 'conv_DMS2DD.cal'.
  4. Follow these steps to run the code above in the Field Calculator:

    A. Add the table containing the DMS coordinates to ArcMap through the Add Data button.

    B. Right-click on the table name > Data > Export and export the table to a DBF file.

    C. Open the DBF table and add items named 'longDD' and 'latDD' to the table, defining these as Double, Precision 18, and Scale 13.

    D. Calculate the field values for 'longDD' and 'latDD' by starting a load of the conv_DMS2DD.cal script to the Field Calculator.

     Change the name of the field in the script to that of the original DMS fields:

    'Change the source field name below
    sField = [Long]

  5. 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.

     Defining the projection permits the data to display in the correct location in ArcMap as an Event layer.

  6. Convert the Event layer to a shapefile.

    A. Right-click the Event layer and select Data > Export data.

    B. Select the output location for the shapefile and type in the name.

    C. Click Save and OK in the Export Data dialog box to create the shapefile.

Related Information


Created: 8/26/2004
Last Modified: 1/5/2012

Article Rating: (1)
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Comments

By Anonymous - 03/16/2011 11:00 AM

The article contains a dead link.

On my desk top the code works as well as that found in in Ianko's Easy Calc (very similar) which doesn't work at all.

Rating:

By Anonymous - 07/19/2005 7:54 AM

Did not work