GPS Essentials

WORK IN PROGRESS

Basic Knowledge

  • Waypoint: A waypoint is simply a unique address for any point in the world, but instead of the traditional street/city/state/zip format we’re used to for road travel, GPS units utilise waypoints expressed in mapping formats such as latitude/longitude or the UTM Grid.
  • Routes are pre-defined paths created from a group of location points entered into the GPS receiver in the sequence you desire to navigate them.Location points can be user generated waypoints or points of interest that have been loaded from a map or from a Garmin program. Routes are created on the computer and/or on the device. Routes Navigate you from point A -> B
  • Tracks act like breadcrumb trails, allowing you to see where you or another individual traveled in the past. This allows you to navigate a path previously taken. But it’s your responsibility to stay on the track, if you wander of your GPS won’t notify you.

UTM vs Degrees coördinates

  • The Universal Transverse Mercator (UTM) is a system for assigning coordinates to locations on the surface of the Earth. Like the traditional method of latitude and longitude, it is a horizontal position representation, which means it ignores altitude and treats the earth as a perfect ellipsoid. However, it differs from global latitude/longitude in that it divides earth into 60 zones and projects each to the plane as a basis for its coordinates. Specifying a location means specifying the zone and the xy coordinate in that plane. The projection from spheroid to a UTM zone is some parameterization of the transverse Mercator projection.
  • Decimal degrees (DD) express latitude and longitude geographic coordinates as decimal fractions and are used in many geographic information systems (GIS), web mapping applications such as OpenStreetMap, and GPS devices. Decimal degrees are an alternative to using degrees, minutes, and seconds (DMS). As with latitude and longitude, the values are bounded by ±90° and ±180° respectively.

    Positive latitudes are north of the equator, negative latitudes are south of the equator. Positive longitudes are east of Prime meridian, negative longitudes are west of the Prime Meridian. Latitude and longitude are usually expressed in that sequence, latitude before longitude.

Important to know is that most maps have both UTM and a form of degrees reference. However the ease of use of the UTM is far more efficient then the complex calculations that need to be made to transfer from UTM to Degrees. Almost every recent map uses UTM or MGRS grid. So if you set your GPS settings to UTM and WSG84: both your physical map and GPS are talking the same language. Also you can transfer locations located on the map into your GPS without coverting.

The North Pole

  • True North (also called Geodetic north) is the direction along Earth’s surface towards the geographic North Pole or True North Pole.
  • The North Magnetic Pole is a wandering point on the surface of Earth’s Northern Hemisphere at which the planet’s magnetic field points vertically downwards (in other words, if a magnetic compass needle is allowed to rotate about a horizontal axis, it will point straight down). There is only one location where this occurs, near (but distinct from) the Geographic North Pole and the Geomagnetic North Pole.
    The North Magnetic Pole moves over time due to magnetic changes in the Earth’s core. In 2001, it was determined  to lie west of Ellesmere Island in northern Canada In 2009, while still situated within the Canadian Arctic,  it was moving toward Russia at between 55 and 60 km (34 and 37 mi) per year. As of 2019, the pole is projected to have moved beyond the Canadian Arctic.
  • Magnetic declination, or magnetic variation, is the angle on the horizontal plane between magnetic north (the direction the north end of a magnetized compass needle points, corresponding to the direction of the Earth’s magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole). This angle varies depending on position on the Earth’s surface and changes over time.
Magnetic variation shown in the legend of a topographic map

In short: your map is based on the True North, your compass will point to the Magnetic North. Depending on where you are on the planet you will need to adapt your compass to bypass this deviation. Most maps give you the necessary numbers to calculate this deviation. You can also download apps or use websites to know the deviation of a certain location. Best is to know how to calculate it.