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This page is all about wilderness navigation for hiking, mountaineering and ski touring.

Maps

NTS 1:50,000 map series

NTS Index Map of SW BC

Most recreationists in Canada use the National Topographic System (NTS) 1:50,000 mapsheet series. These maps are convenient scale that covers a large area but also shows sufficient detail.

Each NTS map has a 3 part code. For example: 92 J/3 is the map for Brandywine Falls, the Brew Hut and Rainbow Mountain. The whole country is divided into a grid of 1:1,000,000 scale maps. Southwest BC is map 92 (9 = map index from east to west, 2=map index from north to south). All smaller maps that fit within map 92 are prefixed with the code 92. Each 1:1,000,000 map is divided up into 16 1:250,000 mapsheet that are index with a letter from A-P in a back and forth fashion. Then each 1:250,000 map is divided up into 16 1:50,000 mapsheets that is index with a number between 1 and 16, again in a back and forth fashion. All this is very confusing, so the government has created index maps that show the relationships of the the smaller maps to the larger ones.

NTS maps come in 3 different forms. Usually each map is only available in one form, but sometimes you have a choice

• Tyvek maps are the best. They are printed on Tyvek which is waterproof and highly tear resistant. The only down side is it is very hard to write on them with a pen or pencil. Tyvek maps are a relatively new addition to the NTS map series. The number of maps available in Tyvek seems to be increasing, which is a good thing.
• Printed maps are pretty good. The image quality is the same as the Tyvek map series but the paper is less durable. These maps have been available since the beginning of time.
• Plotted maps are the worst. These maps have been printed on an inkjet printer by a 3rd party map printer and it shows. Image quality is poor and the paper is the same as on the old printed maps. Don't buy these maps if you don't have to.

NTS map contour intervals are 100 feet on the old maps, and 40 meters on the new maps. Bold contours are every 500 feet or 200 meters. The metric maps use the NAD83 Datum (same as WGS84) whereas the maps with contours in feet use the older NAD27 Datum. All maps are marked with Lat/Long around the edges and a 1km UTM grid across the entire map.

TRIM 1:20,000 map series

The BC Government has it's own set of maps that are known as TRIM maps. These maps use the same indexing scheme for the 1:1,000,000 and 1:250,000 levels as the NTS maps. However, the TRIM series uses 100 1:20,000 mapsheets to cover a 1:250,000 map. TRIM maps alway have 3 digits in the 3rd part of the code so that the codes are alway distinct from NTS maps. For example 92 J/1 is a 1:50,000 NTS map and 92 J/001 is a 1:20,000 TRIM map.

The data for TRIM maps is available online through www.maps.gov.bc.ca. This is great for viewing maps but printing you own maps from this is very difficult.

TRIM map contour intervals are 20m, and bold contour intervals are 100m. All maps use the NAD83 datum (which is the same as WGS84)

Latitude and Longitude

The earth is essentially a sphere, so it makes sense to measure your position in terms of angles. Latitude is your north-south position. The equator is 0 degrees, the north pole is 90 degrees north and everything else is somewhere in between. Each degree is divided into 60 minutes, and each minute into 60 seconds (written like this: 49 30'45"N). For convenience, a nautical mile is one minute of latitude.

Longitude is your east-west position, measured from some old observatory in England. Longitude is demarkated in the same way as latitude using degrees, minutes and seconds. The distance between two lines of Longitude varies with Latitude, getting smaller and smaller as you move towards the poles. This makes calculating distances between two points based on their Lat/Long coordinates troublesome.

It is always necesary to specify E or W with longitude and N or S with latitude, although in all of North America it is always N and W, so sometimes the N and W are dropped.

UTM Grid

Sometime in the 1970s (nobody knows for sure since GPS was a US military project) somebody decided to map the round earth with a square grid. In order to make it fit, every once in a while the whole grid turns and starts over. The result of this effort is a square grid where the grid lines do not always line up with the true cardinal directions N,E,S,W. However, unlike Lat/Long, the grid is consistently spaced - grid lines are always 1km apart which is a significant advantage when calculating distances between two points.

The UTM grid is divided into zones based on longitude. Each zone has a particular meridian to which it is attached. Within each zone, the grid is square. As you move north, the zones start to intersect eachother at funny angles.

Position is measure using two measurements : Northing and Easting. Easting is the distance along the grid from you to the central meridian in your zone, in meters. Northing is the distance along the central meridian for your zone from the equator to the grid line you are on. This may be different from your actual distance from the equator, since the grid is only parallel to the equator along it's central meridian.

3 different kinds of North

Maps show 3 different north arrows and the relationship between them. True north is the direction to the north pole, and the edges of NTS and TRIM maps are aligned to true north.

Magnetic north is the direction you compass will point. The relationship between magnetic and true north varies with your location and is changing with time.

Grid north is the direction of the UTM grid. The relationship between true north and grid north varies with your location.

Datum

There is no such thing as an absolute location, it is only possible to measure location with respect to some reference point. One such reference point is in Grenwhich, England, which is presumed to be 0 degrees longitude, but many others have been established because it's easier to construct a map from a nearby reference point than from a far away one. Prior to satellite navigation with GPS, when refernce points other than Grenwhich England are used, the location of the reference point with respect to Grenwhich, England is estimated but cannot be determined exactly. Each of these reference points (together with it's presumed Lat/Long) is called a datum. Maps are constructed by surveying from the reference point outwards. Because the relative positions between the reference points for various datums is hard to measure (across the ocean for example), there is often an offset between the coordinates of a particular location between one datum and another datum.

Another part of a datum is the presumed shape of the earth (some sort of ellipsoid), and the presumed location of the center of the earth (which does not necesarily match the real center). Among other things, this part of the datum is used to establish a reference point for measuring elevation above sea level far from the ocean.

• WGS84 is the datum that the GPS system is based on
• NAD83 (North American Datum 1983) is essentially the same as WGS84
• NAD27 (North American Datum 1927) is a single datum that is commonly used for all of North America. The reference point is Meades Ranch in Kansas[1]. The difference between NAD27 and NAD83/WGS84 is consistently about 300m horizontally. Vertical differences between the two datums vary substantially.