Reading Topo Maps

[+LeeinVa1]

Currently i use topo maps that i print out using UTM and grid squares, if i set my gps to utm i can use my coordinates from the gps and locate myself on my map. I have never learned how to use a standard topo map, 7.5 to locate my positon using dd.mm.ss or dd.mm.mm. the problem i have is trying to determine how to measure the distance inside the grid squares. anyone out the there can provide a simple explanation on how to do this? thanks

[Tahosa and Sons]

I have a scale that measure Lat & Long and have not used it once I found out how to use UTM's. Lat & Long is useless on a TOPO map, but UTM's are fairly accurate. And if you have a program like NAT GEO's TOPO one can do some neat things with maps and plotting with UTM's.

[+Team Trail Walker]

I have always used Lat/Lon to plot points on a map using this Map Tool. I print 7.5' maps with NG Topo! and place a Lat/Lon grid right on the map.

 

To test the set up when I first purchased TOPO! I plotted several points at prominent features on the map. Loaded the points into my GPSr and headed out to find them. I was impressed at the accuracy. I have also worked the opposite way. Once I hiked a trail that crossed into a wilderness area. I took a reading with my GPSr (etrex yellow) and plotted the point on the map. The point was within 100' of the boundary mark on the map.

 

Give it a try.

 

*edit* The site, linked to above, has explanations on how to use the tools.

Edited March 10, 2006 by Team Trail Walker

[+The Jester]

... Lat & Long is useless on a TOPO map, but UTM's are fairly accurate. ...

Hmmm... How did we get along before UTM? One thing to keep in mind when using USGS printed 7.5 topo maps - they use NAD27 datum.

 

There are several different UTM & Lat/Lon map tools available. You may have to 'fiddle' with the map size when printing your own to get one of the scales to match your map. They make reading grids much easier.

[Suscrofa]

???

To determine the distances on a map is very easy with a simple ruler, for ex on topo map 1/25000 one cm is 250m (250m is 25000 cm !), scale 1/100000, 1 cm is 1 km. To determine the UTM loc, just add the m values to the grid (left and lower).

[+reveritt]

... Lat & Long is useless on a TOPO map, ...

I emphatically disagree! The problem that most users nowadays have with Lat/Lon and USGS topos is that they print a portion of the map, and therefore do not have the Lat/Lon scales along the margins. I have been using paper topos for many years, and never bothered with the UTM grid. You just need a decent plotting tool and a pair of dividers.

 

If you want to locate or measure against an electronic topo, you need to do it in the application, which handles the coordinate transformations.

[+fizzymagic]

Lat & Long is useless on a TOPO map, but UTM's are fairly accurate.

Really stinks that the world is round, doesn't it? Life is so much easier when you can pretend it's flat.

[+dino_hunters]

USGS topo maps do NOT have lat long grids printed on them, only tick marks on the edges. The red grid lines you normally see are section lines used to survey the state.

 

If you look at the edges of a usgs topo map (paper copy) it will have UTM grid tick marks. Using those, and a ruler, you can easly draw in the utm grid lines on the map, using a straight edge.

Edited March 10, 2006 by dino_hunters

[+dino_hunters]

expertgps will plot any kind of grid you want, lat long, utm , using any datum, like wgs 84, or nad27 ect.

[+CharlieP]

Topo maps usually have the grid squares (if any) on the UTM scale, so if I want to find my position I change the GPS to output UTM. But my nautical charts use large scale Lat/Long grids and I make my own chart tool from a piece of paper at least as large as the grids. I use the scale on the side of the chart to make tick marks on the paper (usually tenths of a minute) starting from the corner. The Lat units will be different from the Long units unless you are close to the equator. Then to read coords for a point, I position the paper on the closest grid line and read the fractional value from the tick marks. The paper should be labeled with a North arrow so you position it correctly.

[+reveritt]

Topo maps usually have the grid squares (if any) on the UTM scale, so if I want to find my position I change the GPS to output UTM. But my nautical charts use large scale Lat/Long grids and I make my own chart tool from a piece of paper at least as large as the grids. I use the scale on the side of the chart to make tick marks on the paper (usually tenths of a minute) starting from the corner. The Lat units will be different from the Long units unless you are close to the equator. Then to read coords for a point, I position the paper on the closest grid line and read the fractional value from the tick marks. The paper should be labeled with a North arrow so you position it correctly.

That's one way. The traditional way is to use dividers to lift the distance off the chart and take it to the scale on the edge. That way you don't have to make a "chart tool" for every chart.

[+CharlieP]

That's one way. The traditional way is to use dividers to lift the distance off the chart and take it to the scale on the edge. That way you don't have to make a "chart tool" for every chart.

 

Ever try to use a pair of dividers in a small boat in 5 foot seas with the chart on your lap? You will only do it once.

[+reveritt]

That's one way. The traditional way is to use dividers to lift the distance off the chart and take it to the scale on the edge. That way you don't have to make a "chart tool" for every chart.

 

Ever try to use a pair of dividers in a small boat in 5 foot seas with the chart on your lap? You will only do it once.

Yes! It's right after that that I bought a GPS.

[n0wae]

... Lat & Long is useless on a TOPO map, ...

I emphatically disagree! The problem that most users nowadays have with Lat/Lon and USGS topos is that they print a portion of the map, and therefore do not have the Lat/Lon scales along the margins. I have been using paper topos for many years, and never bothered with the UTM grid. You just need a decent plotting tool and a pair of dividers.

 

If you want to locate or measure against an electronic topo, you need to do it in the application, which handles the coordinate transformations.

If your map has UTM grids then a UTM grid overlay is the easy way to go. Most of the Colorado maps I purchased in the 90's didn't have grid lines and like Tahosa I didn't like the Lat/Lon tool and never used mine much. To prepare a 7.5m Topo map find any two Lat,Lat or Lon,Lon marks and measure the distance in mm. Take that number and divide by 15 and you get the distance for 10 seconds. After you make a template (One for Lat and One for Long) it's easy to mark the margins of your Topo. I used a GPS 100 and Lat/Long margins on my maps to navigate for years and to map jeep roads. It works just fine and is quite accurate unless you Latitude changes too much. In that case I just made another Lat template for the new area I was in. If I needed improved accuracy I used a portable drafting table with T-square and triangle. Far from useless!

[+wildearth2001]

If you are only interesting in using your GPS coords to find your position on the map, you could make it even easier by learning advanced orienteering skills, once you get the hang of that stuff you dont even need a compass, just the map and your brain and you will always know where u are at. The downside is that this method is usless if you want to take your position off the map and put it into the GPS. As for a real answer to the OPs question, I personally use UTM if I am gonna use maps/gps together in the field but like everyone else has said get a good scale and Lat/Long works as well if you make sure to print the tic marks.

[+The Jester]

USGS topo maps do NOT have lat long grids printed on them, only tick marks on the edges. The red grid lines you normally see are section lines used to survey the state.

 

If you look at the edges of a usgs topo map (paper copy) it will have UTM grid tick marks. Using those, and a ruler, you can easly draw in the utm grid lines on the map, using a straight edge.

You can do the same thing using the Lat/Lon tick marks.

 

And with the right map tool (matching the scale of your map) you don't need dividers - of course, using UTM you don't have to do the funky "twist the tool" to match the Lon lines - but UTM has it's fun as you get near the edges of the sections.

 

I know with NG Topo! you can print maps with any size/style grid you want (it's real fun to put a one meter grid on a state map!).

 

And with a little work, you can plot yourself on any topo map, without grid lines or tick marks. Just store the waypoints of some of the major features on the map (mountains, landmarks, etc.), use your GPSr to give you the bearing to said point, and draw your triangulation lines like we did with map and compass. The nice thing about that it works in any weather, you don't have to see the landmarks.

[+LeeinVa1]

Thanks for your help, i knew if i waited long enough someone would come up with the the information i needed. I just checked some of my topo maps, the UTM tick marks are on the borders and making the grids was easy, guess i am on my way now. thanks again for all the help.

[+TotemLake]

That's one way. The traditional way is to use dividers to lift the distance off the chart and take it to the scale on the edge. That way you don't have to make a "chart tool" for every chart.

 

Ever try to use a pair of dividers in a small boat in 5 foot seas with the chart on your lap? You will only do it once.

Yes! It's right after that that I bought a GPS.

[+edscott]

If you are only interesting in using your GPS coords to find your position on the map, you could make it even easier by learning advanced orienteering skills, once you get the hang of that stuff you dont even need a compass, just the map and your brain and you will always know where u are at. ....

 

...or the GPS for that matter. Just read the map and find the cache. Works for me. Only problem are those pesky multi-caches. Let's see now, 60 meters east and 50 north or is it 50 and 60 ? darn.. just fell off the edge of the map.

[+LeeinVa1]

290 people checked this post and i got 18 replies, apparently i was not the only one having problems.