How to Calculate Scale Factor using UTM WGS84 Coordinate System

Question

Hi,
 
Am Ali and I live in Sierra Leone.
 
I would like to know how to calculate the Scale factor in my region (UTM Zone 28 with central meridian of 15 degrees), given a control point of latitude 8.680658 degrees, longitude -12.51276 degrees and elevation of 168.754 above mean sea level.

SelvakumarGanesan · Answer

You can download and use the program from the following link, it shows scale for any position of Lat-Long

http://www.ngs.noaa.gov/TOOLS/utm.shtml

Web site owner: National Geodetic Survey (NGS)

Ali_AhmadJanjua · Answer

Hi Melita,

Thanx very much for the comment, and am sure this will help.

Cheers,

Ali.

MelitaKennedy · Answer

Hi,

Am Ali and I live in Sierra Leone.

I would like to know how to calculate the Scale factor in my region (UTM Zone 28 with central meridian of 15 degrees), given a control point of latitude 8.680658 degrees, longitude -12.51276 degrees and elevation of 168.754 above mean sea level.

ArcGIS Desktop doesn't have a tool to calculate the point scale factor for a map projection like transverse Mercator. The US National Geodetic Survey has a tool that will convert the convergence and scale factor for NAD83 (which uses GRS80). The scale factor will be practically the same for WGS84.

Northing       Easting       Zone  Convergence  Scale Factor
960443.960  773700.612   28     0 22 32.26     1.00052717

If you want the point scale factor for the Sierra Leone 1960 datum (based on Clarke 1880), you'll have to find a different tool.

The scale factor due to a map projection doesn't have anything to do with the elevation at the point. That makes me wonder if you're looking for something like a "combined scale factor" that includes elevation. Here's an excel spreadsheet that does it, but it would also need adjusted if you want the information based on Clarke 1880 rather than GRS80/WGS84.

Melita