DIRECTION W140003XQ STUDENT HANDOUT - United The John A. Dutton Institute for Teaching and Learning Excellence is the learning design unit of the College of Earth and Mineral Sciences at The Pennsylvania State University. Do not use the diagram to measure a numerical value. Figure 6-18. 1800 0 obj <>stream CONVERT c. Determine the magnetic azimuth from your location to the distant known point. The straight edge method is used when a compass is not available. Converting to a magnetic azimuth when the G-M angle is greater. (b) From the base of the grid-north line (prong), draw an arbitrary line (or any azimuth line) at a roughly right angle to north, regardless of the actual value of the azimuth in degrees (Figure 6-9). The closer the point is to the grid central meridian and to the equator, the smaller the correction. Going from the known (line The military protractor, GTA 5-2-12, contains two scales: one in degrees (inner scale) and one in mils (outer scale). The back azimuth of 180 degrees may be stated as 0degrees or 360 degrees. Location. Label the borehole azimuth with reference to each system. The magnetic north is usually symbolized by a line ending with half of an arrowhead (Figure 6-1). An arc indicated by a dashed line connects the prongs for true north and grid north. To express direction as a unit of angular measure, there must be a starting point or zero measure and a point of reference These two points designate the base or reference line. b. ''LN =j*'U80 The most commonly used are magnetic and grid. Declination is the angular difference between any two norths. Intersection, using map and compass. Draw a magnetic prong from the apex of the grid-north line in the desired direction (Figure 6-9). Ab = A - 180 Draw an arrow for Grid North using an exaggerated angle east or west of True North showing the grid convergence angle (be sure of the sign convention of the grid convergence value used, for example does a west convergence angle put Grid North west of True North or visa versa?). 9 0 obj<>>>/MediaBox[0 0 612 792]>> x]Yo#7~`C?JAXHYd6@Aefl_]~{uOv:e#Y7evu (1) When working with a map having an east G-M angle: (a) To plot a magnetic azimuth on a map, first change it to a grid azimuth (Figure 6-10). 2296 0 obj <>stream Ab = A + 180 Who's going to be the first hunting 'celebrity' or Youtube personality to put their foot down and stop using cellular cameras? Azimuth and A = Azimuth, Determine the grid coordinates to the desired accuracy (Figure 6-17). All the convergence angles west of the Central Meridian are negative. You should have written down your Grid Azimuth (GAZ). Add the GM angle to convert a grid azimuth into a magnetic azimuth. Underneath the compass is a small standard screw slot that an accompanying tool will adjust to whatever your declination is, East or West. Personally, I prefer maps that use the MGRS (Military Grid Reference System) which is similar to the UTM, but scaled in 1:25,000 & 1:50,000, which is what I learned in during active duty. The surface location to target direction will therefore be referenced to Grid North. Figure 6-16. The azimuth, 260, is more than 180, so subtract 180 from the azimuth. WebThe University of Akron : YOU BELONG HERE! (2) endstream endobj 1784 0 obj <>stream Degree. How many minutes does it take to drive 23 miles? Magnetic Azimuth = 90 degrees True Azimuth = Magnetic Azimuth + Declination True Azimuth = 90 + (-15) = 75 degrees Figure 6 Example 2 Grid Convergence Grid convergence is an angle between True North and Grid North. WebThe GM angle is used to convert magnetic azimuth to grid azimuth and vice versa: Grid azimuth - determined with a protractor and is measured from grid north. Disclosure: Some of the links above are affiliate links. YMMV. When an azimuth is plotted on a map between point A (starting point) and point B (ending point), the points are joined together by a straight line. be Northeast relatively.) This method can be used at night. d. Convert the magnetic azimuth to a grid azimuth. Rotate the straightedge until the known position on the map is aligned with the known position on the ground. hb```"?f" !E5r|x:s9DvD*\^b"/mKG@@al>;/UbD-m- 1?(RA)@'7$Z4 ER#cJCg((`R``A*x Do you add or substance when converting a grid azimuth to magnetic azimuth in the westerly GM angle? Azimuth Reference System Conversions - Rig Worker The magnetic azimuth is determined by using magnetic instruments, such as lensatic and M2 compasses. The angle can be clockwise or counter clockwise from True North to Grid North. The magnitude of the correction angle depends upon its location within the grid and its latitude. Draw an arc from the grid prong to the magnetic prong and place the value of the G-M angle (Figure 6-9). Theyll either have tick marks on them that you can use to provide your own grid (as I have done and commenters have suggested (Tip: Use very thin map marking pens and dont use red ink red disappears when using a red light) or complete grid lines. d. Conversion. 260 180= 80 Step 2. The difference between magnetic north and grid north is often referred to as grid magnetic angle and it not only varies from place to place, but changes with time. f. The location of the user is where the line crosses the linear feature. e. Applications. On a plane surface this would be the shortest distance between two points]. (c) Keeping the index at this point, align the 0- to 180-degree line of the protractor on the vertical grid line. WebTo convert a magnetic azimuth to a grid azimuth, add the value of the G-M angle to the magnetic azimuth. is, must be between zero and 360 degrees. This is easy to remember. That's why I believe the adding and subtracting methods are the wrong solution that can be completely avoided. source:https://www.americanpartisan.org/2019/04/essential-skills-converting-grid-and-magnetic-azimuths-how-and-why/, on CONVERTING GRID AND MAGNETIC AZIMUTHS HOW AND WHY, CONVERTING GRID AND MAGNETIC AZIMUTHS HOW AND WHY, https://www.americanpartisan.org/2019/04/essential-skills-converting-grid-and-magnetic-azimuths-how-and-why/, **Battle Drill/Ruck** May 6th 0900-1600 @ Lewis & Clark Trail, **Land Nav** Jan 28th 0900-1600 @Rockwoods, **Land Navigation** Dec. 10th 0900-1300 @ Spencer Road Library Room #212. For a better experience, please enable JavaScript in your browser before proceeding. When I was taking a land nav course in the Army I was told this would vary depending on what part of the world you were in. the back azimuth, and 3) the correct back azimuth must be in the to arrive at the starting point. Using a protractor, draw a line for the back azimuth on the map from the known position back toward your unknown position. Once accurate magnetic declination and grid convergence angles are acquired, all that is needed to change reference systems is to add or subtract these angles from one another. This gives you a grid azimuth of 77 degrees. (f) The inclusion of the true-north prong in relationship to the conversion is of little importance. endstream endobj startxref WebAdd the GM angle to convert a magnetic azimuth into a grid azimuth. You Brilliant people, who have, Below, we explain the trend for those non-Spanish speaking/understanding viewers Thankfully, @babycakes607 explained the trend, In William Shakespeares Romeo and Juliet the character Mercutio is prosaic about love and considers, Hostility to immigrants isnt new to the United States. WebPlease note that the sum of the grid azimuths (in red) at station Fink and station D266 is 360 degrees. Known= 270 mag 3. A simple mathematical mistake could cause disastrous consequences. endobj grid azimuth = geodetic azimuth The directional software packages will at minimum handle UTM and Lambert conformal conic convergence. This needs to be taken into account when navigating with a map and compass. When Magnetic North lies to the west of True North, the magnetic declination is said to be westerly, and if to the east, easterly. dy|zn/_|\`dA/xo_vMS@"/9F}6DQ%u>.]l.ny,Vx~#oWCO1[KAVG9m4DyM*7vp`x~\^ ]S,6 hb```$O eah``dFg9-GbEi|x Convert quadrant/bearing readings, including declination and grid convergence, to a 0-360 degrees azimuth system. So, its good to check the on line or other sources for up to the date declination numbers. ( d) To measure an azimuth, turn your entire body toward the object and point the compass cover directly at the object. Do Eric benet and Lisa bonet have a child together? Considerations for Downhole Survey Azimuths The answer is that you can use a compass or an app like Google Maps on your phone to find out the grid azimuth. For your convenience, you can use a UTM Universal Transverse Mercator AKA USGS 7.5 minute map. is the correct back azimuth. Therefore, This is a direct result of the grid north lines being parallel with each other. Good question though. Apply the mathematical formula to convert a magnetic azimuth to a grid azimuth. Declination diagram with arbitrary line. Introduction to Land Navigation.pdf - UNC Charlotte Army ROTC Alaska is more from what I recall. There is true north (the northern axis around which the earth rotates), magnetic north (the direction compasses point, which changes slightly every year) and grid north (the somewhat arbitrary point where all of your grid lines would converge if your map could extend all the way to the North Pole. a. Using knowledge point #3 above, the correct result will be the (5) Repeat 3 and 4 using a second known position. knowledge that 1) the back azimuth is the opposite direction of the You are using an out of date browser. Figure 6-9. As the request is for the back azimuth, then what is wanted is grid azimuth Converting to a grid azimuth when the G-M angle is greater. Using it is pretty simple: Place the center over the point on the map youre using to determine which azimuth youre going to travel on, square the protractor to a. (1) Add an easterly G-M angle to a magnetic azimuth to obtain a grid azimuth. %%EOF CR 98 JORDINATE CON Grid: Add 60 When using the straightedge method (Figure 6-19). endobj 6 0 obj H=k0w14}slPZHZ:u_-XC]}>2FD8\70}@YC"/QRpP>eEF^fxFh One note provides instructions for converting magnetic azimuth to grid azimuth; the other, for converting grid azimuth to magnetic azimuth. The grad is a metric unit of measure found on some foreign maps. Another unit of measure, the mil (abbreviated ), is used mainly in artillery, tank, and mortar gunnery. xr0A{K;M64%X GqJ8u_~E ,E}\x6%aX@Bl8p endobj 3 0 obj<>>>/MediaBox[0 0 612 792]>> This equationmustbe memorized if you dont have a declination adjustable compass in order to stay accurate and end up on or near the coordinate youre aiming for on the last leg of your navigation. a. Subtract the GM angle to convert a grid azimuth into a magnetic azimuth. I really hate to stir the pot but--. Resection with straightedge. <> Your current quad will be drastically differant from your 1950s quad. (b) To use a magnetic azimuth in (c) Convert a magnetic azimuth when the G-M angle is greater than the magnetic azimuth (Figure 6-15). Then, what exactly is a grid azimuth? Plotting an azimuth on the map. To convert degrees to mils, multiply degrees by 17.78. c. Grad. How To Convert Magnetic Azimuth To Grid Azimuth What north and how? Such procedure is important when working with a map for the first time. ' vuxcwxXONIq$eC CRFRERH>QF4J#[~CO]U26#iB(V]vLa`'xLa1?Ro~& While the relative positions of the prongs are correct, they are seldom plotted to scale. Given this knowledge and the variable definitions Ab = Back The G-M angle value is the angular size that exists between grid north and magnetic north. Determine the grid coordinates to the desired accuracy. endobj Figure 6-19. NORTH IS 0/360 AZIMUTH EAST IS 90. b. Grid-Magnetic Angle. endstream endobj 1783 0 obj <>stream What is the Grid Azimuth? You need to know that if your declination is East, it means that Magnetic North is East of your location. For greater accuracy, the desired method of resection would be to use three or more well-defined locations. The magnetic declination correction is the angle between the horizontal component of the earth's magnetic field lines and the lines of longitude. The grid north for a particular map is usually chosen so that it deviates very little from the true north]. Remember, when taking a reading of a mountain then transfering it to your map, you must do the opposite of what you did when you took a reading from your map. (1) With Notes. This value will be written in the map margin (in both degrees and mils) beside the diagram. I'll be doing it. &n7n_n mI6C. A protractor is used to measure the angle between grid north and the drawn line, and this measured azimuth is the grid azimuth (Figure 6-4). 10 0 obj Basically, once you determine what your Magnetic Declination is, you simply use the provided tool, adjust the declination reading to correspond with that number (either East or West) and use your compass on the map as well as when shooting your azimuth. (d) Determine the value of the G-M angle. In some cases, there are no declination conversion notes on the margin of the map; it is necessary to convert from one type of declination to another.