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Planning a Backcountry Trip with USGS Topo Maps

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The U.S. Geological Survey’s 7.5-minute topographic maps cover the whole country in a grid of sheets called quadrangles, or quads. They show the shape of the land in enough detail to plan a route off the beaten path, and they are public domain. Here is how to read them, pick the ones you need and carry them on your phone.

US Topo and the older maps

US Topo is the current USGS series: 7.5-minute quads at a scale of 1:24,000, published as GeoPDFs with contours, roads, trails, water features, place names and a UTM/MGRS grid. USGS revises them over time, and the edition date is on each sheet.

The Historical Topographic Map Collection holds the older USGS topographic maps as scans. They are worth a look for history and for features the newer sheets may not carry, but they are not current: roads, trails and land status may have changed since they were drawn. The Cartahaven store carries the current US Topo editions.

Reading a 7.5-minute quad

  • Scale 1:24,000: one inch on the printed sheet is 2,000 feet on the ground. A quad spans 7.5 minutes of latitude by 7.5 minutes of longitude, about 8.6 miles north to south and roughly 6 to 8 miles east to west in the lower 48 (narrower farther north).
  • Contour lines join points of equal elevation. The contour interval, the height between two lines, is printed in the margin; it differs from sheet to sheet with the terrain, so check it on every quad. Every fifth line is drawn heavier and labeled with its elevation (an index contour).
  • Spacing is steepness: lines close together mean steep ground, wide apart means gentle. Lines bending into a V point uphill along a stream or gully, and downhill along a ridge or spur.
  • The margin has the legend, the date, the names of the neighboring quads, and on many sheets the magnetic declination. Declination changes over time, so for compass work get the current value for your area from NOAA’s magnetic field calculator.

Planning the route

  1. Find every quad the route crosses, plus the neighbors of any you might bail out into. Routes have a way of running off the edge of a sheet.
  2. Work out the climbing. Count contours on the steep stretches, and note where the route crosses lines closely spaced.
  3. Mark water, camps and exits: streams and springs (check they are perennial, and expect dry ones late in the season), flat ground for camps, and the trails or roads you can leave by.
  4. Check who manages the land and its rules. A topo doesn’t settle land ownership. Check the land manager for permits, fire restrictions, closures and current trail conditions.
  5. Leave a plan with someone at home: route, camps, and when to call for help.

Carrying the quads on your phone

The current US Topo quads are in the Cartahaven store as free GeoPDFs from the USGS topo maps listing; they download straight from the USGS National Map. When USGS publishes a newer edition of a quad, it shows up as a free update. Find them by browsing topographic maps, by park, forest or state, or with backpacking maps. On many of the USGS map pages, “Try it now” opens the quad in the map app in your browser with no account.

  • Every map for a trip at once: in the map app, “Get maps for an area” takes a place and a distance around it and lists every store map that covers it; signed in, you can download the free ones and the ones you own together. From a map already in your library, its ⋯ menu has “Get store maps for this area”.
  • Plan a route: in Tools, “Plan a route” follows the trails, paths and roads of the offline background map, with live distance and climb, and saves as a track to follow.
  • Elevation and slope: the app downloads elevation for the area around each map, so a track’s elevation profile works offline, and Map layers has slope angle shading worked out from it. It is coarser than the contours on the sheet, so treat it as a guide.
  • Public land: in the US, the app saves public land boundaries (USGS PAD-US) for the area around each map, so you can tap the map to see who manages the ground, offline.
  • Off the edge of a sheet: while it follows your position, the app opens your next quad when you walk onto it.
  • Grid and bearings: Map layers lays a UTM, MGRS or lat/long grid over any quad, and “Walk a bearing” in Tools draws a compass line, magnetic or true, from where you stand.
  • Timing: routes and tracks show an estimated time at your pace, and the turnaround alarm warns, while you record or follow a route, when to head back to be out by sunset or dark. Trip check-in in Tools emails the person at home your plan if you haven’t checked in by your return time.

Your phone is a tool, not your only one. Carry the quads on paper (or a printed copy) and a compass too, and know how to use them. Batteries die, phones get wet.

Before you lose signal, open every quad once to make sure it is downloaded. More in using GeoPDF maps offline. Hunting the area? See legal shooting light and the hunting unit pages.