GPS and UTM maps

How to convert between GPS coordinates and the UTM map grid reference system

Last summer, in 2010, we we had a good time on the lakes and trails up at Algonquin Provincial Park. It was a time when smartphones just started to get smart. Our Garmin car GPS and the Algonquin Provincial Park Map were our two sources for planning excursions. But the two are not compatible. The Algonquin Park Map shows a grid at the scale of 1:80,000 (1 mm = 80 meter). The topo maps from NRC are either 1:250,000 or 1:50,000.
The car GPS is based on the geographic coordinate system, taking the spherical shape of the earth into consideration. The Algonquin Provincial Park Maps is flat and uses the UTM coordinate system, taking the two dimensions of a paper into consideration.

If you are familiar with the UTM (Universal Transverse Mercator) and GPS (Global Positioning System) coordinates and all you need is a way to get your hands on maps from National Resources Canada (NRC), we have all the instructions and links on our Digital Topo Maps from NRC page.

If you are not much interested in the details of UTM system and need the conversion done on-the-fly, buy a handheld GPS that does the conversion for you. You can find up-to-date information by searching for 'mobile gps for hiking'. You may also want to pay attention to the Geocaching feature. We never hunted for a treasure yet, but we like the concept. We use an app on our Andoid phones to do the calculation, it is the UTM_Lat-Lon. The app is simple and functional.
Don't count on your cell phone. You may have a GPS enabled phone, but you may not have reception. If you don't turn off the phone when you leave civilization, the battery may drain in just a few hours due to searching for a cell tower. No matter what, you will need a map that goes with the GPS app. And for that, make sure you downloaded the maps ahead of time and save it on the device.
IMPORTANT: When you use a tablet or laptop without a SIM card, the GPS function will not work without Internet connection. That holds true for iPad, Surface or any other tablet we checked (as of 2021). To make them work, you have to get an external GPS receiver.

If you didn't run out yet to buy a GPS and are still reading, here we go.
GPS actaully refers to the satellite system operated by the United States Space Force. GLONASS is the equivalent system operated by Roscosmos State Corporation for Space Activities. The third system is BeiDou operated by China National Space Administration.

First, how accurate are GPS? Garmin states that they are accurate within 10 meters (Source Garmin 2021). It is also important to know that the GPS signals have to lock in which takes time. Don't move your GPS unit for at least 20 seconds. Keep in mind that your body will block some of the signals.

When you compare the results from several units, take the average. We did some tests over several days back in 2011. Exact same location and height. The results differed within about 3 meters on the same device, and up to 25 meters between the devices. Don't pay too much attention on the altitude, this number is way out, the units show differences of up to 50 meters.
With these 'rounding' differences in mind, we need the GPS coordinates with max 3 digits (eg N45 33.869 W78 33.134) or max 5 digits in decimal (eg Latitude: 45.56448 Longitude: -78.55223). Changing the last digit in the coordinates will move you about 1 meter. For practical purposes, a 25 meter discrepancy between devices is not going to make a difference when finding your favourite spot on the map. That's half a millimeter on the map.

Lets have a look at the Algonquin Provincial Park Map. You can buy them in the park.

Zone and Datum on map The UTM system is based on a Zone and a Map Datum. This information is printed somewhere on the map.
This map here is from Zone 17 and uses the Map Datum NAD 27. It is important for the conversion, but all the system we looked at defaulted to the correct settings.

Somewhere on the map you'll find the base numbers for the coordinates (see below).
Make sure you adjust the base number correctly.
The number 7 00 000 for points to the right, 6 99 000 for points to the left.

Coordinate prefix on map

Coordinate prefix on map Easting: The gate is @ 70 + 4 as per grid (the 4 is 400 meters). Prefix this with the 7 (actually 6 because it's counting down) from the base number on the map. The final Easting is 6-70-4-00 = 670400.
Northing: The prefix is 50 plus the 34 + 2 from the grid. The final number is 50-34-2-00 = 5034200.
Now enter this number in a converter such as the one listed below from Montana State University & Yellowstone National Park and you get the coordinates. To verify, enter these coordinates in google maps.

Converting the coordinates
The conversion tool we like most can be found at Research Coordination Network (source 2019). The input form supports the different formats for the coordinates in degrees and decimal.
Look for an app that can convert the GPS to UTM, they are available for Android and iOS.

Algonquin Park Coordinates
As we mentioned in the beginning, our interest for GPS and maps started when we were in our canoe in the middle of the Algonquin Hailstorm Creek. We had the GPS coordinates but no clear reference to find our location on the map. After all, it's one big marsh and the passage with flowing water changes possibly every year. Well, we found the exit :-)
If you are looking for the Algonquin GPS coordinates, they are in the Algonquin Park GPS Coordinates posting. Most coordinates for the Algonquin Park are there.

First published on April 25, 2011
Last revised on January 05, 2019
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