How to Read Grid Coordinates on a National Geographic Topographic Map

It's like shooting fish in a barrel to blow this off as "duh, I know how to utilize a map." But you probably don't — at to the lowest degree not beyond the basics. This beginner'southward guide to map reading teaches you how to get the most out of your road atlases and topographic maps.

Summary:

• Scale is how zoomed in or out a map is, such as one inch equaling one mile.
• The first thing you should look at in a road atlas is the legend, which explains what lines and symbols mean.
• Other of import atlas features: the alphabetize, which gives page numbers for all major locations and tables that help estimate travel times.
• Map coordinates help yous identify and communicate locations.
• Important standard coordinate systems to know: Universal Transverse Mercator (UTM), Military Grid Reference System (MGRS), and the MGRS noncombatant equivalent, the US National Grid (USNG).
• MGRS and USNG are roughly equivalent for most purposes and both are based on UTM.
• UTM, MGRS, and USNG use eastings and northings in meters for coordinates. You lot e'er read those grids by going right (easterly), and so upward (northerly).
• USNG coordinates are composed of a 3-character zone designation, a two-letter code designating a 100,000-meter area, easting coordinates, followed by northing coordinates, like so: 18TWL8563111326.
• You tin can drop some of the coordinate numbers when less accurateness is required. If yous and another political party know the general area, y'all could abbreviate the above coordinate to WL8563111326 or even 8563111326.
• If less accuracy is required, you tin cut off the last digits of the easting and northing coordinates: 856113. Never round UTM, MGRS, and USNG coordinates.
• Contour lines on a topographic map indicate elevation. Shut contour lines indicate steep terrain and wide contour lines indicate gentle slopes. No contour lines mean flat land.
• Topographic map colors: Forested areas are green, h2o is blue, human-made structures are black, etc.

In this guide:

• Reading scale
• How to use a road atlas
• Coordinate systems
• An exercise to do your map grid skills
• Breaking down a USGS US Topo map
• Finding coordinates for an arbitrary location on a USGS map
• How to read contours on a topographic map

Reading scale

Scale defines how many map measurement units equal how many existent world units. The scale besides defines how large of an area the map covers and in how much detail. At that place are three ways maps convey scale:

• A verbal scale, similar 1" = 100'
• An RF scale, which is a ratio of units, similar 1:24,000, which ways that one inch equals 24,000 inches.
• A bar scale, which is a visual representation of the scale. This is the almost of import scale characteristic for navigation.

Here's an instance of a bar calibration. On the top line, a measurement from 0 to one represents a kilometer or ane,000 meters on the map. On the second line, the measurement from 0 to 1 represents i mile on the map. The third line represents feet.

American road maps tend to be in miles, while topographic maps are in meters. You may have seen a military machine motion-picture show where a soldier talks about traveling so many "klicks," which is armed forces lingo for kilometers.

Metric is better to employ in the field because the conversions are easy: 100 centimeters is a meter, 1,000 meters is a kilometer, and 100,000 meters is 100 kilometers. If you're looking at a 1,000 meter filigree, you know that ¼ of the grid is 250 meters. That'due south much easier to calculate in the field when y'all're sweaty and stressed than trying to remember that three miles is xv,480 feet.

How to use a road atlas

Road atlases are somewhat self explanatory, and usually have instructions inside, only hither are some tips.

Fable

The beginning thing you should find in your atlas is the legend, which should be at the very front of the book. It explains what symbols, lines, and numbers mean, and there may be other usage instructions and tips nearby. Make sure to notation how exits and other numbers are presented.

Notation: DeLorme land atlases simply mark exit numbers with blackness text and don't explain that in the fable.

Alphabetize

Atlases prove state-level views with call-outs for large cities. A land atlas has multiple views of the state as well as larger city maps.

Notation the filigree on each page. If you lot refer to the index in the back, it'll requite you folio numbers and filigree coordinates for locations. The Rand McNally and National Geographic national atlases carve up locations by country, with a folio range for each state and then grid coordinates for each location. In DeLorme state atlases, information technology looks similar 74 A-vi, which means folio 74, filigree location A-6.

If you want to expect up Sheboygan in the National Geographic atlas, flip to the Wisconsin entry in the alphabetize, which tells you lot to await at pages 118-119. Then look for Sheboygan, which is marked M12. Plough to page 118, which shows a two-map spread of Wisconsin. Find 1000 on the left and follow it to the 12 on the bottom.

M12 marks the spot.

Estimating distance and travel time

Two useful features of atlases are distance and time travel tables. For instance, on page 27 of the National Geographic atlas, it shows a table of distances betwixt cities in Florida. Say you want to drive from Orlando to St. Augustine. Find Orlando on the left side and follow information technology until Orlando and St. Augustine intersect, which tells you 103 miles.

Atlases accept maps that bear witness travel times between major cities. Find the line that connects the ii cities to become the estimated hours and minutes of travel. If in that location isn't a directly line between 2 cities, follow the path and add together up the time on each line.

Not every urban center is listed on the time map. The National Geographic atlas doesn't have St. Augustine, so you have to guesstimate. Follow the 50-minute line between Orlando and Daytona Beach, then follow the 1:25 line from Daytona Embankment to Jacksonville. Add them together to become 2:15. Looking back on folio 27, St. Augustine is near 60 miles southeast of Jacksonville (the width of a finger is near as wide as the x-mile scale line). Subtract 30 minutes from the travel time to estimate one:45 to get from Orlando to St. Augustine.

There's a more accurate yet more than-deadening manner to measure distance on an atlas. If you await closely at a map in an atlas, you should see trivial numbers by major roads. Some of those numbers should be miles between 2 points — bank check your fable near the front end of the atlas to see what the individual numbers mean. Some numbers are measures of miles while others are exit numbers.

Tip: Y'all can buy credit-card-sized fresnel lenses for cheap, which help you see tiny map details, accept a modest ruler for measuring distances, and tin can fifty-fifty assistance yous start fires.

Planning a road

To chart a road between ii places, beginning make certain you lot take the right map. If yous're traveling from Nashville, Tennessee to Lexington, Kentucky, a Tennessee atlas won't do so you lot'll desire a national atlas.

Start at the smallest scale map possible and so switch to a larger-scale map for more detailed views. A national atlas should have a nationwide interstate map virtually the front of the volume. If you look at the map in the Rand McNally atlas, y'all can see that from Nashville you'd have I-65 north to Elizabethtown and and then have Blue Grass Parkway east to Lexington. Merely which exit number is that?

Flip to the Kentucky pages, find Elizabethtown, and then Blue Grass Parkway, which shows that information technology's go out 10. Follow Bluish Grass Parkway with your finger and you run into that it eventually ends at Highway 60. Turn right at Highway 60, which takes you to Lexington.

Then look at the Lexington callout and find Highway threescore to the west. That takes you to New Circle Route, which loops effectually Lexington. At that place are get out numbers for New Circle Road, then you can selection the one closest to where yous want to become. From there, yous'd want a urban center map of Lexington.

Here's a video showing how to use a road atlas:

The adjacent fourth dimension you make a trip, try plotting a road with a paper map. You tin can check information technology against Google Maps or use your GPS every bit a backup.

Coordinate systems

A map without some sort of grid is just a movie. Exterior of consumer-grade road atlases, there are several standardized systems for identifying and communicating locations, and three yous should know: breadth and longitude, Universal Transverse Mercator (UTM), and the United states National Grid (USNG).

Latitude and longitude

Nearly of us learned about latitude and longitude in school. Latitude refers to the north-south position of a coordinate. Picture show 180 imaginary horizontal lines — 90 north and ninety south — spanning the earth, from the North Pole to the South Pole. Those imaginary lines are chosen latitudes or parallels. If you accept problem remembering, think latitude = ladder, like the rungs of a ladder.

The primal latitude is the equator, which is halfway betwixt the North and South poles. In mod nomenclature, the equator is zero degrees (0°) latitude, and all other latitudes are divers past information technology. The North Pole is at 90°N and the South Pole is at 90°S. All latitudes fall between those two extremes. Each latitude is approximately 69 miles apart, merely since the world is curved, the distances vary a bit.

Longitude defines the east-west position of a coordinate. Picture 360 imaginary lines — 180 e and 180 westward — spanning the earth from the North Pole to the S Pole. While everyone agrees on the equator being the origin of latitude, not everyone agrees on what the primal longitude should be. The Western standard is the Prime Pinnacle, which is the longitude that passes through the British Royal Observatory in Greenwich, England. Nearly longitudes you lot come across volition exist divers by the Prime Meridian. Both extremes, 180°W and 180°Due east, meet in Greenwich.

On the opposite side of the Prime Peak is the International Engagement Line. Information technology'due south the line at which you cross from ane day to the next. (Some countries alter that dateline for political reasons.)

Distance between longitudes varies greatly. They run into at the poles and are furthest apart at the equator.

To add greater precision, latitudes and longitudes are farther divided into minutes and seconds. Each degree is divided into lx minutes and each infinitesimal is divided into 60 seconds. Each minute of latitude is almost a mile.

There are two common ways to denote longitude and latitude. The beginning is Degrees-Minutes-Seconds (DMS). Information technology looks like this:

forty°44'54.384"N 73°59'8.3904"W

For the northern coordinate, that translates to 40 degrees, 44 minutes, 54.384 seconds north. You could simplify it (with less precision) to twoscore°44'54"Due north or you lot could cut out the seconds: twoscore°44'N.

The second common way to correspond breadth and longitude is decimal degrees (DD), which is more estimator friendly. So instead of xl°44'54.384"N 73°59'8.3904"West, you would see forty.764460514309114, -73.98106857921982.

Tip: Paste both forty°44'54.384"N 73°59'8.3904"W and 40.764460514309114, -73.98106857921982 into the Google Maps search field and see where they accept you.

Yous should be familiar with the terms around latitude and longitude considering they come in other systems. Breadth and longitude are used primarily for air travel, sea navigation, and in GPS software.

Universal Transverse Mercator

The curvature of the earth is a pain when working with flat maps. So geographers take devised what are chosen projections to transpose a round surface onto a apartment map.

The downside of projections is that they are inherently distorted. For our purposes, they're accurate plenty, but it's impossible to perfectly translate a sphere into a apartment rectangle.

One of the projections you lot'll come across the most oft is the Universal Transverse Mercator (UTM). Its evolution is credited to the US Army Corp of Engineers in the early 1940s, and is based on the 16th century Mercator projection.

UTM divides the world into 60 longitudinal zones, each representing six degrees of longitude. Imagine taking an orangish, peeling 60 strips of its rind from i end to the other, and and so squishing those strips flat on a tabular array.

The continental U.s.a. spans from UTM zone 10, the westernmost half of California through UTM zone 19, which contains Maine. Each zone is split into the northern and southern hemispheres, so in that location is a 10N and 10S. Each UTM coordinate starts with the zone and hemisphere.

Inside each zone is an contained grid divers non by latitude and longitude, merely by what'due south called eastings and northings, measured in meters instead of degrees. That makes UTM much more useful for country navigation than longitude and breadth.

UTM avoids negative numbers. Running down the centre of each UTM zone is a central superlative, which is an easting of 500,000 meters. An easting of 500,001 meters is one meter to the east of that meridian. An easting of 499,999 is one meter w of that acme.

The central meridian of every UTM zone is marked at 500,000 meters.

In the northern hemisphere, the bottom of the zone is the equator, marked at 0 meters. In the southern hemisphere, the top of the zone is the equator, marked at 10,000,000 meters.

The equator defines the lesser of the grid in the northern hemisphere and is marked at 0m N.

The very bottom-left of any half-zone map is 0mE 0mN. Yous always read UTM maps past going right, and then up, or in geography jargon, easting then northing.

In reality, UTM coordinates look similar this: 18N 585631mE 4511326mN.

That reads as zone 18, in the northern hemisphere. Then identify the easting on the map, which is 585,631. Starting at the zone's central superlative, which is marked at 500,000 meters, you'd look to the correct (east) 85,631 meters. And so yous'd move up (n) four,511,326 meters.

US National Filigree

The United States government has created two spin-offs from UTM: the Military Filigree Reference System (MGRS) and its civilian equivalent, the US National Grid (USNG). They are by and large equivalent, equally long as both coordinates are based on the WSG84 datum (which most are, more on datums in our guide to the best maps). The USNG is meant only for use in the United States and territories, while the MGRS applies worldwide.

(Some other thing to note is that while USNG and MGRS are interchangeable when they both use the WGS84 datum, they're different if the ii maps are using NAD27.)

There are three key differences between UTM and MGRS/USNG:

• MGRS/USNG apply their ain prepare of zones, chosen Filigree Zone Designations (GZD). These stand for to UTM zones, but they supplant the North/S designation with a letter designation to signify latitude.
• At that place is an additional ii-letter of the alphabet 100,000-meter foursquare identification.
• The coordinates are mashed together without any spaces or directional designations.

If we convert our UTM coordinate from to a higher place, 18N 585631mE 4511326mN, into USNG, it looks like this: 18TWL8563111326.

MGRS/USNG use UTM zones, but replace the N/S hemisphere designation with letters that denote latitude, from U in the north to R in the south.

That translates to, zone 18T, Grid Zone Designation WL, and then information technology reads similar UTM: 85,631 meters easting, 11,326 meters northing. The smaller zones and the GZD truncate those meter readings.

The presentation of coordinates is a bit different, but the MGRS/USNG grid and the UTM grid are one and the same. It'due south common to see UTM, MGRS, and USNG used interchangeably, but you lot tin can tell the departure between MGRS/USNG and UTM by the coordinate format.

If y'all're confused, don't sweat. We have some exercises to aid you empathise how the filigree works.

An practise to do your map grid skills

Here are some hands-on exercises to familiarize yourself with the concepts. Assuming y'all're familiar with Google Maps, these exercises will take your existing Google Maps skills and translate those into:

• Working with latitude and longitude in DMS and DD formats
• Converting latitude and longitude to UTM and USNG coordinates
• Finding USGS maps
• Reading and understanding everything on a USGS map
• Locating yourself on a USGS map
• Extracting USNG and UTM coordinates from a USGS map

Convert latitude and longitude from Google Maps into USNG coordinates

Permit's look up a national landmark in Google Maps. National landmarks are marked on USGS maps, and then you lot get an idea of how accurate your grid navigation skills are. We'll use the White House every bit an instance.

Visit Google Maps on a desktop spider web browser. In the search field, type White House and choose White House on Pennsylvania Artery. Google Maps zooms into the White House with a scarlet pin mark on information technology. Right-click (or Control-click on a Mac) and cull the first option, which copies latitude and longitude coordinates in decimal form to your clipboard.

The coordinates Google Maps copies to the clipboard are besides long for the conversion tool we'll utilize and you'll cease up with inaccurate coordinates, but Google Maps can as well fix that.

Get back to the Google Maps search field, select everything in the field, paste in the latitude and longitude you but copied, and press Enter or click the search icon. Await beneath, and you lot'll have two sets of latitude and longitude coordinates: one in DMS, and another set in the correct decimal form. The White Business firm is located at 38°53'52.three″N 77°02'11.half-dozen″W in Degrees/Minutes/Seconds (DMS) or 38.897860, -77.036551 in Decimal Degrees (DD).

Note: Sometimes Google volition give y'all slightly different coordinates, so if yours don't match up exactly to our example, don't worry. Merely verify on the map that the pivot is in the correct place.

Visit NOAA's NGS Coordinate Conversion and Transformation Tool (NCAT), which converts breadth and longitude to UTM, USNG, and other coordinate formats. Endeavor entering coordinates both ways to get a experience for it.

When entering coordinates in DMS format, type the numbers without whatever other characters. NCAT separates degrees, minutes, and seconds with a dash that it inserts for y'all. When you enter longitude, brand sure to prepend it with a zero to enter it correctly.

Once you've inputted the breadth and longitude, click Submit.

Look under Lat-Lon-Height, which gives coordinates in DMS and decimal formats. Compare those numbers to Google Maps and make sure they match. The formats are slightly dissimilar, only the numbers should friction match up. Zoom in on the map to make sure the pivot is on the White House.

Look nether UTM/USNG, which gives the zone, northing, and easting. Then look for the entry for USNG, which should exist 18SUJ2339007413. (Again, if yours is slightly unlike, it'southward not a big deal equally long equally your marker is on the White House.)

Reading USNG coordinates

Let'south intermission down 18SUJ2339007413:

18S: This is the USNG filigree zone designation, and it aligns with the UTM zone. So UTM and USNG zone 18 are the same slice of the globe, except UTM would designate it equally 18N for the northern hemisphere and USNG designates it as 18S for being in the eye breadth of the Us.

You can run across the difference past plugging in the latitude and longitude into Montana State University's converter, which gives both the standard UTM and USNG (which it calls NATO UTM). UTM 18N 323390mE 4307413mN and USNG 18SUJ2339007413 are the aforementioned coordinate in different systems.

UJ: These 2 messages ascertain the regional area within the zone, a 100,000-meter or 10-kilometer square. If you're communicating with someone inside that full general vicinity, you lot can drop the starting time five characters of the USNG coordinate for simplicity, similar so: 2339007413.

23389: This is the easting coordinate in meters. For getting your map bearings, you want to at kickoff focus on the get-go two digits, 23, which are marked on the map grid. You will approximate the last three digits on the map.

07410: The last five digits are the northing coordinate in meters. Focus on the get-go two digits, 07.

Use USNG coordinates to download a USGS Usa Topo map

At present, re-create those coordinates, 18SUJ2339007413, and visit the USGS Shop Map Locator. The USGS provides free topographic maps in PDF course you tin print out or you can gild a re-create for a nominal fee.

Paste 18SUJ2339007413 in the Map Locator field and wait for the car-proposition to appear underneath, which should say 18SUJ2339007413. Click that. A blue marking with a card appears on the map. Click View Products.

On the correct, a listing of available maps appears. Gyre down to find the 1 labeled 2019 and click View PDF to download information technology. Exist enlightened that this is a large download, well-nigh 84 MB.

Detect a location on a USGS US Topo map

Open that file, ​​DC_Washington_West_20191122_TM_geo.pdf. If your computer is too ho-hum to display it, you could have it printed, simply its full size is 24-by-29 inches. (More on map printing in our guide to the best maps.)

USGS maps are enormous.

Zoom in as far as yous can while still displaying the coordinates on the sides of the map. Let's find the White House.

Tip: At a map scale of ane:25,000, 1 centimeter equals 250 meters. At 1:50,000, 1 centimeter equals 500 meters.

When finding UTM or USNG coordinates on the map, you first go right so up. In other words, start with easting and and so movement up to northing. Await at the bottom of the map and you lot should see a serial of numbers from sixteen to 26 (ignore the 3, 000, one thousand, and Eastward for now). The first two digits of our easting coordinate is 23, so find 23. The beginning two digits of our northing coordinate are 07, so trace up from 23 along the line until yous accomplish the 07 line. Yous're at present on the i,000-meter (1 kilometer) square that contains the White Business firm. Let's narrow that downward further.

Inside the 23, 07 square, nosotros want to again motion right and so upwards to find the White House. But at that place aren't whatever lines to follow! Thankfully, because nosotros're working with the metric organization, everything is base-ten.

Take another wait at the easting coordinate, 23390. Yous're already on the 23, but at present you need to motion 390 meters to the right from the 23 line. The square represents 1 kilometer, which is ane,000 meters. Let's circular 390 upwards to 400. 400 meters 40% of a kilometer, so from the bottom-left grid corner, move 40% to the right.

Now you need to notice the northing coordinate, which is 07413. You're on the 07, and then you lot need to move 413 meters north (or up). Again, about xl% upwardly from the 07 line. Your finger or marker should be right near on the White House. If not, try again.

Try the same method to find other landmarks, similar your firm. Practice until you lot can comfortably find the correct map and the desired location on the map.

Tip: A map grid tool helps you lot take precise measurements on UTM and USNG maps.

Find adjoining USGS maps

As large as USGS maps are, they comprehend a relatively pocket-sized area, 100,000 meters (100 km). Our map has the White Firm, just not the Pentagon, which is just south of the White Business firm. The map itself tells us how to find adjoining areas.

Look nearly the lesser of the map for a grid of nine squares. Inside the grid is a red rectangle, which denotes the current quadrangle you're viewing. Around the center rectangle are numbered rectangles cogent bordering maps. The legend tells y'all which number aligns with which map. The Pentagon is southward of the White Business firm, and so nosotros want map vii, Alexandria.

If you lot go dorsum to the USGS Store Map Locator, the marker may still be there. Otherwise, search for the White House location over again and so zoom in on the map until the filigree appears. Each grid entry should reflect what you encounter on the map itself. Double-click in the desired grid square, Alexandria, to reveal a blue marker and a card where yous can click View Products. Download that map, VA_Alexandria_20190823_TM_geo.pdf.

If y'all line up the maps so the Washington Westward map sits on top of the Alexandria map and align the filigree lines, they should friction match upwards perfectly. Find how the northing coordinates terminate at 06 on the bottom of the first map and so keep downwardly to 05 at the summit of the Alexandria map.

Breaking down a USGS U.s.a. Topo map

Now that you know how to read the grid, allow's await at all the other parts of a USGS topographic map.

In the upper-right corner is the name of the map in all caps, like WASHINGTON WEST QUADRANGLE. Underneath that is the general surface area followed by "vii.5-infinitesimal series." That ways the map covers 7 minutes and 30 seconds of latitude and longitude.

In each corner are breadth and longitude coordinates in decimals, which correspond to the betoken in each corner. So if the upper-left corner has 39.0000°, -77.1250°, those are the coordinates for that corner of the map. Y'all could use that coordinate along with a special ruler to determine your latitude and longitude on any point on the map, only information technology shouldn't exist necessary.

Too in the corners are the total UTM coordinates, presented with subscripts, like and so: 316000mE and 4318000mN. The first, 316000mE, simply means that corner is 184,000 meters west of that UTM zone's central height. Call up, the central top is marked at 500,000 meters, then you lot'd subtract the 316,000 from 500,000 to get 184,000. Likewise, 4318000mN means that point is 4,318,000 meters n of the equator.

Subsequent grid numbers omit all of that for clarity. On our map of the White House, follow 316000mE to the right to reach 17, which can be expanded in your head to 317000mE or 317,000 meters easting. Unremarkably, yous can but refer to the grid numbers.

At that place is some important data in the lower-left corner telling you the dataset and geodetic system used. On modern USGS maps, that should be NAD83 and WGS84. Whenever comparing with another map, corresponding with another party, or using an online conversion tool, you want to brand sure that information is the aforementioned.

Then there's text like this: 1 000-meter grid:Universal Transverse Mercator, Zone 18S. That's just bones information: each grid is ane,000 square meters, information technology aligns with the UTM organization, and information technology shows the USNG zone you lot're viewing.

Below that shows years when each piece of information on the map was last updated. The newer, the ameliorate.

To the right of that is a declination diagram that lets y'all orient your compass so due north on your map aligns with magnetic north. Beneath that is a box reminding y'all that the map represents 100,000 foursquare meters, shows the two-letter of the alphabet regional lawmaking, and then the Filigree Zone Designation. These are upside downwards for some reason, as they put the regional code above the GZD.

In the bottom-heart of the map is the scale nautical chart. To the correct of that is the vicinity map, which shows how your map fits into the surrounding area. Below that is the small grid that shows how that map fits in with connecting maps. Finally, on the far right is a legend that shows road data.

Finding coordinates for an arbitrary location on a USGS map

You know how to take a set of USNG coordinates and find a location on the map, only can you exercise the contrary? Let's say you're stranded in the forest but have triangulated your location with a compass and landmarks. Could you successfully communicate your position to rescuers?

Open the map of West Washington again. Let'south use the centre of the Naval Observatory every bit our signal, since it's large, circular, and near the eye of the map.

Take hold of a pen and paper. Wait on the bottom of the map for the GZD and write it down. So write down the two-letter region code but higher up information technology. Now we just demand the easting and northing coordinates.

Recollect, to find a spot on the map, you get right, and then up to find the correct foursquare to search in. So to discover the coordinates for the Naval Observatory, down and and then left to find the lower-left grid foursquare corner information technology sits in. It sits just above 10 on the northing line and to the correct of 20 on the easting line.

And so now y'all should have a coordinate that looks like this: 18SUJ2000010000. That gets you lot close, simply allow'due south dial it in a bit.

The Naval Observatory sits mostly to the right of the xx northing peak, with a sliver of it by 21. We're going to guesstimate that the middle is about 70% past 20. So that updates the coordinate to 18SUJ2070010000. Don't just copy our estimate, make your own and write it downward.

The Naval Observatory sits on pinnacle of the 10 northing line, so gauge the center to exist near twenty% higher up information technology, updating the coordinate to 18SUJ2070010200. Again, make your own guess! That should dial the location in to near a 100-meter radius.

Now check your result to see how you did. Go dorsum to NCAT and next to "Select the type of horizontal coordinate:" select USNG. Now paste or punch in the coordinate yous derived, which marks it on the map. Zoom in on the map to come across exactly where it landed.

We got well inside the Naval Observatory but didn't quite hit the center. Did yous? Just like shooting a gun, it takes practice and skill to hit your marker. Only the point of this do is to get comfortable enough with the system and with making decent estimates so that y'all can convey your position to a reasonable radius. A beginning responder would have much more to piece of work with this coordinate than if they were searching bullheaded.

How to read contours on a topographic map

Profile lines are important when traveling in the wilderness because they give you a sense of what the land is actually like. Let's say you're lost in the woods. You lot angulate your position on the map and place a road two miles west of your location. Y'all decide to take the shortest path in that location to expedite your rescue. You walk half a mile west just to stumble upon an impossibly steep ravine. Now what?

Oftentimes, the shortest path isn't the quickest. If you can read the profile lines you can nautical chart a path that keeps you on flat terrain, or at to the lowest degree on the same meridian then you're not stuck trying to climb a mount or descend into a steep valley.

Take a close wait at a topographic map, like i from the USGS. You'll meet brown, squiggly lines all over. Those are the contour lines. Each contour line forms a closed loop, so if you start at 1 betoken on the contour line and follow it, you'll eventually end upward in the same spot.

To make sense of information technology, imagine a layer cake, where each layer is smaller in bore than the one underneath. The outline of each layer would be a contour line.

Another classic method is to draw lines on your hand with a marker. Brand a fist with your not-dominant mitt. Draw a circle around each knuckle. Then draw concentric circles around your fist on contour. When you lot're done, open your mitt and lay it apartment. The lines on your hand are contour lines.

There are a few different types of contour lines on a topographic map, but the first one to know is alphabetize lines, which are thicker, and are marked with the summit in feet. Only every fifth contour line is an index line, so how practice we know the difference in elevations? If y'all wait on your map, in that location should be a contour interval specified somewhere, usually 20 feet. So the space between each contour line is 20 feet or whatever your map's interval is. (If the interval is anything other than 20 feet, you're probably looking at especially flat or rugged terrain.)

Those lighter, unmarked profile lines are called intermediate contour lines.

The fundamental thing to remember nigh contour lines is: the closer together they are, the steeper the terrain. If an surface area has no contour lines, that means it's flat. Widely spaced contour lines indicate a gentle gradient. When navigating, you should try to avoid crossing a space where profile lines are tightly grouped. Wait at a topographic map again and try to identify flat spots, gentle slopes, and steep areas.

Relatively apartment areas may accept dashed contour lines chosen supplementary contour lines, which indicate half of the contour interval. They limited mild changes in elevation.

Another rule to remember almost contour lines is that they never bear upon or intersect, with one exception: at a vertical wall or a cavern.

There are five major terrain features you can identify on topographic maps:

Hills: Hills are represented past concentric contour lines with a pocket-size, circular contour line in the center. They often look kind of like the concentric rings of an archery or firearm target. Sometimes the peak of a hill is marked with a symbol, like a triangle or an X.

Valleys: A valley is a long groove in the country with high ground on three sides. At that place is often a h2o source in a valley. Expect for V- or U-shaped lines on the contour map. The airtight point of the Five or U always points to higher ground.

Saddles: A saddle is a low bespeak between 2 high areas. Await for an hourglass shape in the profile lines.

Ridges: A ridge is a sloping line of high ground. It may be represented by V- or U-shaped lines or past a series of hills connected past saddles.

Depressions: Low points in the ground surrounded past higher ground. Contour lines for depressions are represented by tick marks intersecting the contour line.

In that location's an old military pneumonic to remember these major terrain features: Subconscious Valley Ranch Salad Dressing.

And there are three pocket-sized terrain features to know:

Draws: A describe is like to a valley but has no level ground, which makes draws difficult to navigate.

Cliffs: Cliffs are sudden drib-offs in terrain. They're marked either by closely spaced contour lines with tick marks or past the rare occurrence of profile lines touching.

Spurs: Spurs are similar to ridges in that they're sloping lines of high basis, but they're shorter and usually jut out from ridges.

At that place are also two supplementary terrain features:

• Cuts: A cut is a human-fabricated cut through raised ground, ordinarily to level ground for roads or railroad tracks. Cuts are represented past contour lines along the cut with inward-pointing tick marks.
• Fills: The opposite of a cut, a make full marks where people filled in a low area, over again usually for a road or railroad track. Fills are represented with outward-facing tick marks.

On USGS maps, cuts and fills are oftentimes represented by a red line (cogent a route) cut through elevated terrain.

Of import colors on a topographic map

Finally, there are important colors to recognize on topographic maps. You already know brown signifies profile lines. Permit'due south look at the others:

• Blackness: Man-made structures similar buildings
• Blue: Water
• Green: Forests and wooded areas
• Red: Boundaries or roads

In that location may be other features marked on your map, but they're non universal. Check your map's legend. The USGS publishes a guide to their topographic symbols, which marker things like campgrounds and swamps. However, if you know how to read everything listed in this guide, you tin suss out most things on a topographic map.

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Source: https://theprepared.com/survival-skills/guides/maps-101/

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