# How do you get the grid coords. off a map?



## brushbuster (Nov 9, 2009)

I have a question for you map experts. I know how to get headings, adjust for grid to mag north using declinations. but i cant for the life of me figure out how to calcualte grid coordinates. I understand about the long and lat lines. But lets say i want to get the coordinates for a penninsula on a lake. How do you go about plotting the coordinates? P.S. I dont want to use a computer. I want to do it the old fashioned way.


----------



## bronc72 (Nov 25, 2008)

The map has to have them printed on it. Then you must remember this phrase "right and up". You read first to the right for the first part of the coordinate, then up for the second part of the coordinate.


----------



## bronc72 (Nov 25, 2008)

If you were on the peninsula, you would find some landmark or land feature that stands out, say a tall hill and shoot an azimuth to it with your compass, then find at least one more prominent feature and get an azimuth to it.
Then find the two features on the map and plot the back azimuth to your position for each feature. The line will cross at your position. It gets easier after you have done it a few thousand times. It is harder in the woods, open areas like deserts make it easier to see. It heavily forested areas we would send someone up a tree.


----------



## brushbuster (Nov 9, 2009)

On the top and bottom of my map margin are the longitudinal readings they are marked with index marks every 2/1/4 inches and on the sides of my map are the lat readings spaced apart the same as the long. readings.
On the top left corner of the map margins they read like this
81deg 45'0" and then 2/1//4 inches over to the right to the next index mark is another reading that reads 81deg43"45" the numbers keep decreasing in value all the way over to top right corner of map every 2/1/4 inch intervals until it ends with the reading81deg31'15"
The reading are exactly the same at the bottom of the map margins. Ok I get that, but what i dont understand is first of all what do the mumbers mean? are the last two sets of digits in the longit. coord. in feet and inches? secondly in that 2/1/4 inch span between the readings there is a difference of1'15" so if i wanted to read the coordinates between those 2 sets of readings how do I determine what the actual reading is in between the 2 readings? Even more confusing huh?
Let me break it down this way
back up to the top map marging. in the left corner is the first longitudianl coord. it reads 81deg45'0" now go to the right and the next reading is 81deg43'15" like i said the differnce in those 2 numbers are 1'45" so the space in between those two readings are void of numbers. if i put a dot anywhere in between those two longitudianl readings how do i determine what the reading for the dot is?
I hope this makes sense to someone out there.:lol: If i can figure out what the increments are then theoreticaly with that information i could get coordiantes on any part of the map but i just dont know how to get the figures in between the 2 readings.
I know this doesnt make a lot of sense. but its the best way i can explain it. I guess what im trying to figure out is... what is the increments between the 2 readings. My map is at a 1:35000 scale


----------



## brushbuster (Nov 9, 2009)

I got it figured out. I was looking at the wrong set of numbers.


----------



## bronc72 (Nov 25, 2008)

Cool, it is hard to explain, just practice, try doing some geocaches with a map and compass. 
When I was learning land nav at the School of Infantry that was how we mastered it, rather than geocaches there were ammo cans hidden that we would have to find. You will get better at it with practice.
I like a lensatic compass for land nav, it makes getting the azimuth easy and accurate.


----------



## fish_AK (Nov 10, 2009)

brushbuster said:


> I have a question for you map experts. I know how to get headings, adjust for grid to mag north using declinations. but i cant for the life of me figure out how to calcualte grid coordinates. I understand about the long and lat lines. But lets say i want to get the coordinates for a penninsula on a lake. How do you go about plotting the coordinates? P.S. I dont want to use a computer. I want to do it the old fashioned way.


The old fashion way is with a garmin, lol. To find a proPer grid u need the right map. Most maps are not intended for using the military grid system.

Get a 1:50,000 scale map of your area. Google military protractor. These really help measure. Put protractor on map and measure to the right, then up. A 4 digit will get you into a 1:50000 grid square, 6,8,&10 digit grids are more precise. The more digits there are the closer you will be. On a paper map 6-8digit grids are as precise as your gonna get. If you want something better get a garmin.
Outdoor Hub mobile, the outdoor information engine


----------



## tbarden11 (Mar 2, 2011)

On our search and rescue team, we train by using UTM coirdinates. You use a UTM reader with a topo map. Once you get the hang of it, easy to do.

Outdoor Hub mobile, the outdoor information engine


----------



## FredBearYooper (Oct 5, 2009)

I beg to differ on the 8 digit grid being the best your going to get..our FO's can get 10 digits easily..

Outdoor Hub mobile, the outdoor information engine


----------



## 9mm Hi-Power (Jan 16, 2010)

brushbuster said:


> I have a question for you map experts. I know how to get headings, adjust for grid to mag north using declinations. but i cant for the life of me figure out how to calcualte grid coordinates. I understand about the long and lat lines. But lets say i want to get the coordinates for a penninsula on a lake. How do you go about plotting the coordinates? P.S. I dont want to use a computer. I want to do it the old fashioned way.


There are numerous transparent plastic devices for determining grid location on United States Geological Survey (U.S.G.S.) maps as well as devices like "Geologist's Land Locator." They can be bought from Forestry Suppliers Inc. which has a website. They are inexpensive and fairly easy to use once you get the hang of it. The ones I have can only be used, however, on the U.S.G.S. 7 1/2' quadrangles - 1:24,000 scale. Each sheet covers 7 1/2 minutes of latitude and 7 1/2 minutes of longitude. These are the largest scale topo maps generally available for civilian use.









.

You can also get a similar device for determining your Universal Transverse Mercator (UTM) grid location. Latitude and longitude is an angular measure based on the arc of a circle. It is not a linear (feet, inches etc.) measure. UTM is a linear measure and it describes a point in terms of its distance in meters north of the equator and east of the central meridian of the next westerly zone (earth is divided into zones) . 

UTM is generally easier to understand because it uses linear measurements, meters, as opposed to degrees, minutes and seconds of the arc of a circle. Hope this helps.

Also keep in mind that when using the U.S.G.S. topo maps the longitudinal lines on the right and left hand side of the map are not parallel - they're true meridians (1/2 of a great circle) - if you were to project them northerly they would eventually merge at 90 degrees north latitude i.e. the north pole. Also I think your map scale is 1:25,000 not 1:35,000. Some U.S.G.S. topos are 1:24,000 and others 1: 25,000 - not sure why????

Hoppe's no.10


----------



## brushbuster (Nov 9, 2009)

9mm Hi-Power said:


> There are numerous transparent plastic devices for determining grid location on United States Geological Survey (U.S.G.S.) maps as well as devices like "Geologist's Land Locator." They can be bought from Forestry Suppliers Inc. which has a website. They are inexpensive and fairly easy to use once you get the hang of it. The ones I have can only be used, however, on the U.S.G.S. 7 1/2' quadrangles - 1:24,000 scale. Each sheet covers 7 1/2 minutes of latitude and 7 1/2 minutes of longitude. These are the largest scale topo maps generally available for civilian use.
> 
> 
> 
> ...


 Excellent post sir, this explains quite a few things to me that were a mystery.So would the utm on the map be the same reading on a gps if i were to mark a spot with gps?Sorry for my ignorance but i just never got into this much navigation. I only use the little bit of knowledge that i have to get me by ,knowing that there is a bunch of things to learn.


----------



## 9mm Hi-Power (Jan 16, 2010)

brushbuster said:


> Excellent post sir, this explains quite a few things to me that were a mystery.So would the utm on the map be the same reading on a gps if i were to mark a spot with gps?Sorry for my ignorance but i just never got into this much navigation. I only use the little bit of knowledge that i have to get me by ,knowing that there is a bunch of things to learn.


I can't imagine why a UTM coordinate off of a GPS would be significantly different than a UTM coordinate plotted by someone who had the proper tools and knew how to use them.

Looking at the upper left hand corner of your quad you will see a group of numbers that are arranged like this (these are taken taken off of the Addis, MI quad, the figures on your quad will be different but arranged the same): 4929000mN (the font of some of the numbers on the map will be of varying size). Every point on the line that extends easterly from this number is 4,929,000 meters north of the equator. A bit below that will be a group of numbers like 4928. That point is 4,928,000 meters north of the equator. Along the top parallel you will see a figure that is arranged like this: 660000mE - the light brown tick mark or line to the east of the figure is 660,000 meters east of the central meridian of the next westerly zone. Likewise there will be another tick 1000 meters to the east and so on - so every 1000 meters the coordinate is so marked on the map. All UTM coordinates north of the equator will have a northerly and easterly description.

Hoppe's no.10


----------



## PsyopsE6 (Aug 25, 2008)

Read right and up...


----------



## PsyopsE6 (Aug 25, 2008)

FredBearYooper said:


> I beg to differ on the 8 digit grid being the best your going to get..our FO's can get 10 digits easily..
> 
> Outdoor Hub mobile, the outdoor information engine


Hoorah, Staff..we often used 10 when I was the FDC in a Mortar plt, with the, 14th Inf, 25th Inf Div. At Camp McKall we used just 8, which got us past the "draw monster" Airborne


----------



## FredBearYooper (Oct 5, 2009)

PsyopsE6 said:


> Hoorah, Staff..we often used 10 when I was the FDC in a Mortar plt, with the, 14th Inf, 25th Inf Div. At Camp McKall we used just 8, which got us past the "draw monster" Airborne


FDC huh. I'm the mortar plt medic in my company. I can do every job now except FDC. We use a computer system now instead of sights and poles.

Outdoor Hub mobile, the outdoor information engine


----------



## michiganbuck (Mar 11, 2010)

Agree to use of UTM. Once accustomed to its use location and distance from point to point is much easier than with latitude and longitude in degrees. Both are found on a good map. Latitude N/S stays near constant at about 69 miles per degree but Longitude E/W goes from about 69 miles at the equator to zero at the poles. A degree in Michigan is about 69 miles tall and about 48.5 miles wide. UTM stays constant measuring with meters in a simple grid going east and north from a single point. Good to know how to convert meters to feet. Mx3.281= Feet. F x.3048=Meters. Best to mark a map with magnetic north/s/e/w lines in red pen, and to also put the conversion formulas on that same map. When one is in trouble, lost, hot or cold thinking can become difficult and one needs every help aid possible. You can find more about this at kellyroadcamp on the internet. That is my Cheboygan camp&#8217;s web page.


----------

