Quick and dirty VBA code example. This code was written to populate point features with a new UTM NAD83 point based on a latitude and longitude value found in the feature class's attribute fields.
Option Explicit
Public Sub ConvertDDtoUTMNAD83Z12N()
On Error GoTo errorhandler
Dim doc As IMxDocument Dim map As IMap Dim fl As IFeatureLayer Dim fc As IFeatureClass
Set doc = ThisDocument Set map = doc.FocusMap Set fl = map.Layer(0) Set fc = fl.FeatureClass
Dim pPoint As IPoint Dim x As Double Dim y As Double Dim temp As Double
Dim cur As IFeatureCursor Dim fea As IFeature
Set cur = fc.Search(Nothing, True) Set fea = cur.NextFeature
Do Until fea Is Nothing x = 0 y = 0
'get lat and long values from fields x = fea.Value(fc.FindField("Longitude")) y = fea.Value(fc.FindField("Latitude"))
If x > y Then temp = x x = y y = temp End If
Set pPoint = New Point
If x <> 0 And y <> 0 Then
'make a new point and reproject from DD to UTM Dim pSpatialRefFactory As ISpatialReferenceFactory Dim pSpatialRef As ISpatialReference Dim pUTMSR As ISpatialReference
pPoint.x = x pPoint.y = y
Set pSpatialRefFactory = New SpatialReferenceEnvironment Set pSpatialRef = pSpatialRefFactory.CreateGeographicCoordinateSystem(esriSRGeoCS_WGS1984) Set pUTMSR = pSpatialRefFactory.CreateProjectedCoordinateSystem(esriSRProjCS_NAD1983UTM_12N)
Set pPoint.SpatialReference = pSpatialRef pPoint.Project pUTMSR
End If Set fea.Shape = pPoint fea.Store Set fea = cur.NextFeature Loop
