Converting Map Coordinates for Bushwalkers | Latitude, Longitude to/from UTM

Ever wanted to understand what the numbers on the lines on your map are? Does your iPhone app only register latitude and longitude and you need to convert it to UTM (Universal Transverse Mercator) or vice versa. Need to be able to tell your local emergency service the latitude and longitude of your location for a rescue?

There are at least three ways to convert between coordinate systems or formats eg UTM grid references to latitude and longitude

1. using an online Web Converter (see below for examples)
2. install an iPhone App which does it for you (see below for two)
3. change your GPS  coordinate format settings and see the converted result

A word of warning from Professor Dutch

"Caution! Unlike latitude and longitude, there is no physical frame of reference for UTM grids. Latitude is determined by the earth's polar axis. Longitude is determined by the earth's rotation. If you can see the stars and have a sextant and a good clock set to Greenwich time, you can find your latitude and longitude. But there is no way to determine your UTM coordinates except by calculation." (Source: Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay)

UTM

"Universal Transverse Mercator (UTM) coordinate system is a grid-based method of specifying locations on the surface of Earth. The UTM system divides the surface of Earth between 80° S latitude and 84° N latitude into 60 zones, each 6° of longitude in width and centered over a meridian of longitude. Zones are numbered from 1 to 60. " (Source: Clever Applications)

Some Online Web Converters

• The UTM Lat/Lon applet
• Geographic/UTM Coordinate Converter   Chuck Taylor -- (Copyright)
• Degrees, Minutes, Seconds and Decimal Degrees Latitude/Longitude Conversions
• geo2mga:  converts geographic coordinates (lat/long) in decimal degrees format to a UTM grid reference
• mga2geo : UTM to lat/long conversions
• Coordinate Converter

iPhone Apps

Map Tools screenshot

Map Tools By Richard Hoffman

"Map Tools is an iPhone app  that let users to fully utilize coordinates. Map Tools converts coordinates among various datums, coordinate systems and map projections. It also calculates distance between two coordinates. It supports coordinates conversion between geodetic coordinates, UTM, UPS, MGRS and map projections in up to 232 datums. The app is delivered with WGS84 ellipsoid and used as the default datum. You can purchase an add on that will provide you with an additional 232 datums, which include NAD27, ED50, OSGB36, EGSA87, AGD66, AGD84, GDA94 and a lot more." (Source: iTunes Apps)

NB for Australians WSG84 (supplied) and GDA94 are almost equivalent so if you are only using this datum there is no need to buy the extra 232 datums. 

Bit Map by Nixanz 

Bit Map by Nixanz

Bit Map is a map viewer app with some basic GPS features, and simultaneously provides both the UTM and latitude/longitude coordinates in decimal degrees for any point on the uploaded map you are viewing. While it doesn't convert between map coordinate systems, it will give both for any location and datum.

Read my Review of Bit Map

Using your GPS to convert

If you open the settings field on your GPS, you can change between the coordinate formats offered eg UTM to Latitude and longitude etc and all coordinates entered in the original format will then appear in the new.


Social Bookmarking

Visit my Delicious bookmarks to discover some popular web resources on this topic.

Further Reading

• Coordinate System Overview by Peter Dana
• Fundamentals of Mapping Intergovernmental Committee on Surveying and Mapping (ICSM)
• Map Reading J Evans
• Locations in Tasmania  School of Geography and Environmental Studies UTAS
• A Practical Guide TO GPS - UTM by Don Bartlett

This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.