Greetings,

Original post was a very long time ago, but I thought it still important to
post the SUM.   Thanks to all who responded, too many to name.

ORIGINAL QUESTION:
I am tryin gto compare two different point themes, both contain the same
general information, but one is older than the other.  I'd like to compare
the themes.  First, I need to find the points with same ID, but different
locations (some points have been updated using better GPS
equipment/processing).  Second, I need to identify the points that exist in
the old theme, but not the new one.  I've looked at ArcScripts page, and
although there are some scripts that look within one theme, I'm not sure
what to do so I can compare two themes... (avenue beginner)
I do have access to ArcMap and ArcInfo 8.1.

SOLUTION:
Other issues surfaced on the way to getting the solution, in particular the
nasty habit of having our lat and long values truncated in MS Access so we
couldn't do a simple query (which many of you suggested).  The solution that
worked for me was suggested and implemented by Chris Mack (THANK YOU!)  He
sent a VBA script that works in Excel.  Its copied below. Fields in the
table are IDNUMBER, ID_CD, LAT, LONG. Works great for the application that
I'm interested in.  Hope it can help you too.  Thanks again Chris, for your
time.  An alternate solution to use within ArcView is prsented below too,
for those who have a preference.

Public Sub CompareTables()
    'This procedure compares two data tables, checks for new ID entries
    'and flags for coordinate changes.  Data tables to be compared should be
in ascending
    'order (on IDNUMBER, then ID_CD fields).  All blank Lat and Long records
must be
    'removed prior to running.  The search algorithm used for this is very
inefficient
    'as all ranges in the Old Table are compared every time for each record
in the New
    'Table.  A more efficient method of searching and comparing the tables
could involve
    'a Hash table searching technique and compared ranges removed per
comparison
    '
    'Author:    Chris Mack - Coastal Engineer
    '           US Army Corps of Engineers - Charleston District
    '           chris.j.mack@usace.army.mil  [Email]

    'Last Revised:  22 OCT 2001
    '


    'create worksheet pointers
    Dim shtOldTable As Worksheet, shtNewTable As Worksheet
    Set shtOldTable = Application.Workbooks("Compare
Tables.xls").Worksheets("OldTable")
    Set shtNewTable = Application.Workbooks("Compare
Tables.xls").Worksheets("NewTable")

    'declare variables
    Dim rngOld As Range, rngNew As Range, rngCell As Range      'New and Old
Ranges to compare
    Dim strComments As String                                   'Processing
comments
    Dim dblTol As Double                                        'Lat-Long
difference tolerance
    dblTol = 0.00001
    Dim blnFound As Boolean                                     'For New IDs
    blnFound = False

    'create ranges for comparison place holders
    shtOldTable.Activate
    Range("a1").Select
    Range("a2", Selection.End(xlDown)).Select
    Set rngOld = Application.Selection
    shtNewTable.Activate
    Range("a1").Select
    Range("a2", Selection.End(xlDown)).Select
    Set rngNew = Application.Selection

    'compare tables
    For Each rngNew In rngNew

        'initialize comments
        strComments = ""

        For Each rngCell In rngOld

            'check if new ID entry...if not, check if Lat-Long values
changed
            If Trim(rngCell.Value) = Trim(rngNew.Value) And _
                Trim(rngCell.Offset(0, 1).Value) = Trim(rngNew.Offset(0,
1).Value) Then
                strComments = strComments & "No Change"
                blnFound = True

                'now check the Lat-Long values
                If Abs(rngNew.Offset(0, 2).Value - rngCell.Offset(0,
2).Value) > dblTol Then
                    strComments = strComments & ", Lat <> [" &
rngNew.Offset(0, 2).Value - rngCell.Offset(0, 2).Value & "]"
                End If
                If Abs(rngNew.Offset(0, 3).Value - rngCell.Offset(0,
3).Value) > dblTol Then
                    strComments = strComments & ", Long <>"
                End If
                Exit For
            Else
                blnFound = False
            End If
        Next

        'if not found, must be new ID
        If Not blnFound Then
            strComments = strComments & "New ID"
        End If

        'list comments
        rngNew.Offset(0, 5).Value = strComments

        'reset comments
        strComments = ""
    Next

End Sub

ALTERNATE SOLUTION, suggested by Bill Huber (thank you very much, Bill)
This analysis is readily done with joins, calculations, and queries, which
is perhaps why nobody has bothered to offer a scripted solution.

Joining the new theme to the old (using the common [ID] field) will succeed
only for records with matches of ID.  This will show you which IDs do not
appear in the new theme.  Performing the join in the other direction (after
removing the first join) will show you which IDs do not appear in the old
theme.  Both joins show you IDs common to both themes.

To find points with different locations, you need to create [X] and [Y]
coordinate fields.  This is easily and quickly done with Field Calculator
expressions

         [shape].GetX

and

         [shape].GetY

Do this first, then do a join.  You will have to provide a new alias for
the joined [X] and [Y] fields so that they have distinct names.  Call them,
for example, [X New] and [Y New].  Having done this, the query

         [X] <> [X New] or ([Y] <> [Y New])

will select the points with matching ids but changed coordinates.

To perform your second analysis, join the new theme spatially to the old
theme.  The points in the old theme whose [distance] attribute is nonzero
are the ones that do not exist in the new theme, regardless of their [ID]
values.


---
Fritz, Ann M. <AFritz@state.nd.us>