You are here: > ESRI Forums > arcgis desktop discussion forums > Thread Replies

ArcGIS Desktop Discussion Forums

ArcGIS Desktop - Projections, Projection Engine forum

Converting Lat and Long to Nad27   jenny Reinheardt Apr 15, 2005
Re: Converting Lat and Long to Nad27   Dan Patterson Apr 15, 2005
Re: Converting Lat and Long to Nad27   Melita Kennedy Apr 15, 2005
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Converting Lat and Long to Nad27 
Author jenny Reinheardt 
Date Apr 15, 2005 
Message I have several Lat and Longs from a GPS unit and have saved them in an Excel spreadsheet. When I try to convert the data to DBF4, dBase IV for ArcMap my information will not save in the dbf format.

I have attached the data (not all of it) I am currently trying to convert. I started small until I get this figured out.

Am I doing somthing wrong in saving the data or is there another way of converting the Lat and Longs to Nad27 so the point will be a shapefile or coverage?

Thanks Jenny
 
  LatLong.xls (opens in new window)
 
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Converting Lat and Long to Nad27 
Author Dan Patterson 
Date Apr 15, 2005 
Message why not save it as a comma separated values file (comma delimited) and add it using the Add XY Data tool 
  Geomatics, Carleton University, Ottawa, Canada 
   
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Converting Lat and Long to Nad27 
Author Melita Kennedy 
Date Apr 15, 2005 
Message Hi Jenny,

I'm not sure why it won't save in dbf. I was able to save it using Excel 2003. Is that you can't save a dbf file or that the AddXY data tool won't work to convert it to a shapefile?

Anyway, try saving it to a CSV file instead. That worked for me.

I have a few comments on the file format too.

1) Make the LongDD values negative. ArcGIS requires that longitudes west of the Greenwich meridian be negative.

2) I'm a bit confused on the seconds fields. Seconds should be between 0-60, so what's 679? Is it really 06.79? I didn't think about until I had checked one of the DMS-to-DD calculations and entered.

3) If the seconds values are 06.79 or something similar, you may want to increase the number of decimal places in the DD fields. 1 second in the lower 48 states is about 30 meters and is, very roughly, 0.0001 when working in decimal degrees. If you have 06.79 precision in seconds, you should increase the DD precision 5 or 6 decimal places.

4) Since you don't state it, just to be sure! Convert these tables to a shapefile of coverage. You may want to assign them the NAD83 geographic coordinate system rather than WGS84. WGS84 and NAD83 are within a meter of each other. There are more accurate transformations between NAD27 and NAD83 than there are between NAD27 and WGS84. Calling the input data NAD83 will let you use the NAD_1927_To_NAD_1983_NADCON transformation (don't worry about the directionality; the software will handle it automatically).

Hope this helps, and makes some sense!
Melita 
  Melita Kennedy
ESRI Product Specialist