Plotting Points-Latitude/Longitude

[berdan]

A trip to montana a while back got me interested in this sort of land nav. I bought a USGS map of the area we where in as a momento. Since MGRS is the only way of plotting points I was familiar with it got me to wondering how I could go about plotting cooridinates onto the map if it only had LAT/LONG markings. Had a gps at the time so I new the location of where we were but did not know how to plot the LAT/LONG from the GPS to the map, or plot where we wanted to go on the map and then punch it in the GPS. I thought this would be a neet trick to learn if I ever had to use any maps that did not use MGRS.

Here is what I found.

http://www.maptools.com/products/LatLonRulers.html (tools needed)

http://www.maptools.com/UsingLatLon/plotting.html (plotting and measuing LAT/Long)


Would this sort if info have any use? Have any of you found it neccessary to use foriegn maps that only had LAT/LONG? How handy do you think this trick could be?

regards

berdan

[The Reaper]

The conversion technique is taught, or used to be.

Yes, I have used it.

Conversion to MGRS is usually for ground types. The Navy and AF can work off either system, and on large scale maps, frequently do.

TR

[berdan]

Sir

Dont have one of those Lat/Long rules. Without trying it as I am reading the directions it sounds sort of complicated and time consuming. Is it?
What scale maps have you had to use this technique with the most?
Where did this technique use to be taught, basic level map and land nav or at more advanced levels?

regards

berdan

[Razor]

IIRC, USGS 1:24k maps have tick marks along the edges that one can use to draw MGRS grids onto the map, which in turn allow you to use MGRS plotting techniques. Wouldn't that be an easier solution?

[berdan]

Yes sir, it sure would. But respectfully, I can not believe it could be that convenient for all maps/scales one may come across.

1:24,000 1:25,000 1:50,000 1:62,500
1:63,360 1:65,000 1:69,500 1:77,000
1:80,000 1:84,000 1:100,000 1:125,000
1:126,720 1:150,000 1:156,000 1:160,000
1:182,000 1:190,000 1:200,000 1:250,000
1:300,000 1:320,000 1:400,000 1:500,000

Wouldnt those tick marks be for UTM? Is that the same as MGRS? I would still need to get a 1:24,000 ruler/protactor to plot points wouldnt I?


regards

berdan

[Peregrino]

Lat/Lon is not rocket science. They teach Navy E-1 QM (not the same as Army) types how to do it. It is still taught in the "Q" course. It's the universal standard. You can use it with any map, every edition, without converting UTM, MGRS, or any of about 20 other coordinate systems in use around the world. It's the only thing guaranteed (mostly) to work on HN maps. If that's how you have to navigate and you're stuck with a coalition warfare mission, you will be grateful for having learned it. If you want to do anything joint you probably have to learn it. If you're on AD and need to learn it or just refresh your memory look in FM 3-05.212 Special Forces Waterborne Operations. It has a pretty good explanation of the technique. FWIW - Peregrino

Edited to add: You don't need to spend your money on the rulers if you just purchase an architect's scale and use the 10th's division IAW the instructions in the Map Reading (FM21-26) manual. The field expedient methods of creating a scale by marking a tongue depressor or cutting a latitude scale off of a nautical chart and pasting it on the tongue depressor are even cheaper and just as effective.

[lksteve]

Originally Posted by berdan

Yes sir, it sure would. But respectfully, I can not believe it could be that convenient for all maps/scales one may come across.

i work with maps from the USGS, USACE, USBOR, USBLM, USFS and a few from state agencies...every quad sheet i've come across, regardless of scale, has lat/long tic marks...i'm not saying they all do, i'm just saying that everyone i've come across in eleven years as a land surveyor, has...i use lat/long as often as possible...if i can put a project on a geodetic framework, i can give a client coordinates in just about any format, any system, ground, grid, geo-reference, Cartesian XYZ, you name it...

one thing to be aware of ...the older quad sheets will show lat/long in NAD 27 which is based on the Clarke Reference Ellipsoid of 1866...it was great for the northern part of the Western Hemisphere...it varies considerably from WGS 84 (the coordinates you get in a hand-held GPS) and/or NAD 83, which are both based on the Geodetic Reference System of 1980...this model is based on global attributes and is more accurate...

something else to be aware of, regarding the numbers associated with the tic marks on the margin of the map...some maps have UTM coords, some have State Plane Coordinate values, some have both...pay attention to that...at any rate, the projection should be listed (NAD 83 or NAD 27) on the map and if you are using a hand-held GPS, you should be able to toggle your coordinate system to one that matches your map...

[jatx]

For those who may be interested, here's a link to download FM 3-25.26, Map Reading & Land Navigation .