how to convert magnetic azimuth to grid azimuth

In the last post onMagnetic Declination, the impact it has on azimuth/bearing accuracy was described. 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 terminal coordinates program may be used to find the coordinates on the Earth at some distance, given an azimuth and the starting coordinates.. Converting to a magnetic azimuth on a map. xr0A{K;M64%X GqJ8u_~E ,E}\x6%aX@Bl8p Magnetic readings are obtained with magnetic instruments, such as lensatic and M2 compasses. Subtract the calculated backsight reading from the original azimuth reading. Required fields are marked *. The angle can be clockwise or counter clockwise from True North to Grid North. How many minutes does it take to drive 23 miles? %PDF-1.5 % In Colorado, the central meridian is 105 degrees, 30 minutes West Longitude, as shown here, on the left you have station D266 and on the right, station Fink. hTak0+VtHpfePAKcH`#IqIz;KYAA"&8$@,(.Q5{u>-q 1"ora-H>:PB6GDE]>>^M&i6)}}}qfWY@vk This equationmustbe memorized if you dont have a declination adjustable compass in order to stay accurate and end up on or near the coordinate youre aiming for on the last leg of your navigation. A glance at the completed diagram shows whether the given azimuth or the desired azimuth is greater, and thus whether the known difference between the two must be added or subtracted. Using a protractor, draw a line for the back azimuth on the map from the known position back toward your unknown position. Next, you must convert to a back azimuth. the reverse (or inverse) of the azimuth, 223 degrees. endstream endobj 1785 0 obj <>stream WebAzimuth is the angle in the horizontal plane between north and the drillholes direction (or bearing) at the survey station. Going from the known (line Good question though. Known= 270 mag 3. \ P]0oY_&@*rX +Fd$Jc&ym?krede QqMwz%l(Yy 3i%[\ V. Using a protractor, draw a line for the back azimuth on the map from the known position back toward your unknown position. a. 1800 0 obj <>stream The most common unit of measure is the degree () with its subdivisions of minutes () and seconds (). Ab = A + 180 The instructor informed us that here in the US it really wasn't relevant. The magnetic azimuth is determined by using magnetic instruments, such as lensatic and M2 compasses. Figure 6-12. Meridians converge on the surface of the Earth. SOUTH IS 180. stream one that is between zero and 360 degrees. Grid north may be symbolized by the letters GN or the letter y (Figure 6-1). knowledge that 1) the back azimuth is the opposite direction of the Values of magnetic declination change with time and location. How do you calculate Grid North to magnetic north? 2282 0 obj <> endobj To convert a grid azimuth to a magnetic azimuth, add the G-M angle. It is used to locate distant or inaccessible points or objects such as enemy targets and danger areas. When using the protractor, the base line is always oriented parallel to a north-south grid line. c. Field-Expedient Methods. 2217 Earth and Engineering Sciences Building, University Park, Pennsylvania 16802 This angle is the difference between the north and the magnetic endobj General directions, imagery and hand railing features is a more effective way to navigate. The directional software packages will at minimum handle UTM and Lambert conformal conic convergence. WebConvert the Magnetic Azimuth of 65 to a Grid Azimuth. If you plot your grid azimuth on a map and it reads (for example), 180 degrees (GAZ), and you know your local declination is 15 degrees East, and you wish to convert your GAZ to a MAZ, simply subtract the Declination of 15 degrees and youll have a 165 MAZ, or magnetic azimuth that you can use with your compass. For your convenience, you can use a UTM Universal Transverse Mercator AKA USGS 7.5 minute map. { yBeDS#5HXM5B^*`Flm5^TQR!j.AzS!OZhkO\%[mk|lq#N. %%EOF One way to do that is to get the updated magnetic field model of the earth from NOAA (or other sources) and write code to do this calculation based on the user Convergence is the difference between geodetic north and grid north. That's why I believe the adding and subtracting methods are the wrong solution that can be completely avoided. Thank you for your replies guys! Since we dont navigate by stars much anymore we really only care about grid north (what the map says) and magnetic north (what the compass says). stream Swarovski ATC Compact Spotting Scope Review, Helping Mule Deer Thrive: Muley Fanatic Foundation, Growing Big Mule Deer with Wildlife Prof Randy Larsen. G-M angle. If you have a magnetic azimuth of 270 degrees, and the G-M angle is 8 degrees, your grid azimuth will be 262 degrees. The magnetic declination correction is the angle between the horizontal component of the earth's magnetic field lines and the lines of longitude. In this example, the known azimuth is 270 magnetic. e. Applications. Web(a) To plot a magnetic azimuth on a map, first convert it to a grid azimuth (Figure 6-13). (b) Place the index of the protractor at the point where the drawn line crosses a vertical (north-south) grid line. UTM Grid North is said to be "X" number of degrees either east or west of True North. <> In this post, were going to look at the how and why of converting grid (or map) azimuths/bearings to magnetic azimuths/bearings and vice versa. Doesn't matter if you're in the northern or southern hemisphere. Figure 6-13. With the rise of technology, true maps, compasses, and land nav will be a thing of the past. This is because 2 degrees and 362 degrees are located at the same point on the azimuth circle. To convert a magnetic azimuth to grid azimuth, subtract G-M angle. If you have a magnetic azimuth of 270 degrees, and the G-M angle is 8 degrees, your grid azimuth will be 262 degrees. WebStep 1. As per the map diagram, to convert a magnetic azimuth to a grid azimuth, you substract the gm angle. endobj *!o$8EAbMZIU&G3V`o! 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. Its the little black pincer looking thing. Determine the grid coordinates to the desired accuracy. When using it. (2) Put your finger on the grid north line, now move it to the magnetic north line. Webc. is, must be between zero and 360 degrees. True North (geographic North) - based on the earth's rotation around its axis and is used to describe relative direction. However, the sum of the geodetic azimuths (in green) at station Fink and station D266 is not 360 degrees. How to convert magnetic azimuth to grid azimuth. Do Eric benet and Lisa bonet have a child together? Grid convergence as calculated by the directional software package is the angular difference in degrees between True North and UTM Grid North. Figure 6-15. If you moved left you should add the angle between grid and magnetic; if you moved right, you should subtract. the back azimuth, and 3) the correct back azimuth must be in the 3 0 obj A grid correction converts azimuth readings between the True North systems and the specified grid system. hbbd``b` @ b*? Figure 6-16. 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?). This protractor represents the azimuth circle. The magnitude of the correction angle depends upon its location within the grid and its latitude. Azimuth and A = Azimuth, WebThe Azimuth Calculator is an incredibly simple tool you can use to determine the azimuth between two specific points on earth. This north base line could be true north, magnetic north, or grid north. Proceed as follows: a. Orient the map using a compass or by terrain association. 0 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. PRECISION LIGHTWEIGHT GLOBAL POSITIONING SYSTEM RECEIVER, Map Reading and Land Navigation REFERENCES. 4 0 obj ]od`l`hPh``` " K053NRhU@$4 ;3t0$202EV1/bera`9~H20D(Uf TO The most commonly used are magnetic and grid. PM Milestone Project Management Templates, Toolface Orientation - Drilling Engineering. WebTo convert a magnetic azimuth to a grid azimuth, add the value of the G-M angle to the magnetic azimuth. When measuring azimuths on a map, remember that you are measuring from a starting point to an ending point. _k6 u7PO3+i_yF(igS|pVGXW~o6zom6 8bl_FP)T iN5;SIlw-KKwj{kLx!:E"Ux++syH9Fj- 5V -PY.f;!eOa$*^ TRdNb8ds)Rjn9TKT{y&wN4# g Have students construct an azimuth-back azimuth line through each point until each end of the line hits a map margin. If your west of the agonic linean imaginary line that runs vertically, west of the Great Lakes and west of Florida (Google agonic line for more detail).you can use the acronym M.U.G.S. Neither points straight at the North Polethat is called true north. However, it is not necessary to know where true north is to avoid getting lost in a combat area. endobj OtoPro SoundGear Phantom and Impulse Review, Vortex Razor HD 4000 GB Rangefinder Review, Toric UHD 2.5-15x44mm FFP Hunt Series Riflescope Review, Hunting Big Mule Deer after Mid-October with Cliff Gray. The conversion (add or subtract) is governed by the direction of the magnetic-north prong relative to that of the north-grid prong. The rules for converting azimuth angle to true azimuth are summarised in the following table: Examples: If latitude is 55 o N, LHA is 145 o and azimuth angle is 120 o then true azimuth is 360 o Z i.e. Thus to convert from a magnetic bearing to a Grid North reference you would subtract 8 23. There are others; I prefer the Map Tools Super GTA protractor. First, a word about grid maps. Ab = A - 180 To convert degrees to mils, multiply degrees by 17.78. c. Grad. (2) GN 4 3 1. On the State Plane coordinate grid, north is always parallel with the central meridian, but at the points on the Earth, north is along the meridian that passes through them. <>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 10 0 R/Group<>/Tabs/S/StructParents 1>> Theyre ok to use; theyre typically in 1:24,000 scale, and you need to ensure your map tools correspond in scale. (3) Determine the magnetic azimuth to the unknown position using the compass. Determine the grid coordinates to the desired accuracy. How do you convert magnetic azimuth to grid azimuth? azimuth and 2) 180 degrees either added or subtracted will yield 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. The consequence of not converting or adjusting for declination is not reaching your objective..or worse, getting hopelessly lost, which might be terminal, depending on your location and the scenario you find yourself in. The declination diagram is used for these conversions. Figure 6-18. %PDF-1.5 % This needs to be taken into account when navigating with a map and compass. Draw an arrow pointing east (azimuth of 90) for an arbitrary borehole azimuth reference. The direction to the north magnetic pole, as indicated by the north-seeking needle of a magnetic instrument. "'pGX. The simplest way available to man right now is to get a compass that has an declination adjustable feature, such as the Sunnto MC-3. or Figure 4. This is a direct result of the grid north lines being parallel with each other. Intersection is the location of an unknown point by successively occupying at least two (preferably three) known positions on the ground and then map sighting on the unknown location. Several field-expedient methods to determine direction are discussed in Chapter 9, paragraph 5. While this seems a simple task, misunderstandings surrounding the relationship between these references can cause a target to be missed. Most of the declinations are listed on each USGS quad but from an accuracy issue they change so what year is your quad. This is TED, speaking on behalf of The English Dictionary. Convert a magnetic azimuth of 347 to a grid azimuth (using a 5Westerly G-M Angle) Answer: 347 - 5 = 342 Answer : 347 - 5 = 342 9. :Qa0I J4 (3) Lay a straightedge on the map using a known position as a pivot point. (5) Repeat the above steps at position (B) and check for accuracy. The magnetic north is usually symbolized by a line ending with half of an arrowhead (Figure 6-1). NORTH IS 0/360 AZIMUTH EAST IS 90. 11K views 8 years ago How to convert from a grid azimuth to a magnetic azimuth. Draw an arc from the grid prong to the magnetic prong and place the value of the G-M angle (Figure 6-9). (2) To plot an azimuth from a known point on a map (Figure 6-7), (a) Convert the azimuth from magnetic to grid, if necessary. (c) Make a mark on the map at the desired azimuth. (1) Place the protractor index where the azimuth line cuts a north-south grid line, aligning the base line of the protractor directly over the intersection of the azimuth line with the north-south grid line. If you're using a regular map with a declination diagram this will always work. be Northeast relatively.) A back azimuth is the opposite direction of an azimuth. Figure 6-9. When converting azimuths into back azimuths, extreme care should be exercised when adding or subtracting the 180 degrees. endstream endobj startxref As the request is for the back azimuth, then what is wanted is All the convergence angles east of the Central Meridian are positive. (6) The intersection of the lines on the map is your location. (d) Read the value of the angle from the scale; this is the grid azimuth from point A to point B (Figure 6-4). This means how to measure a direction - or azimuth - on your map and Such procedure is important when working with a map for the first time. ^ni`H2pI35%S8lKXoboAJXT/k]3 @[J Most well proposals are generated from rectangular coordinates derived from the UTM or local grid system. hb```$O eah``dFg9-GbEi|x a. The reason you need to subtract a value from grid to get magnetic is that there are actually multiple norths. b. The military protractor, GTA 5-2-12, contains two scales: one in degrees (inner scale) and one in mils (outer scale). h[k0`+namhZ*Cbo?N6 ^cXODeQ GJp2iE"JO!/^UgCF97_X]!A(pOXZ,|J;cT-Ve;TOwgRC1x6o1ruqeS{AuG_zPK$H,oZ xsc.mUL.w$& 4 0 obj <>stream 4. The shortest WebSelect and give grid coordinates for three points on the map; list azimuths to be followed in the construction of a line through each point. The chosen sign convention displays Grid North as "x" number of degrees east or west of True North. H[k0e0Zu(fW9QKq:.LJ)~OBhmUEz]@F|;xv?H'F07@F{d;F#: F8hMg$/[?Y% FC4s~ujTzF8[4ZOEOi[nkJ . A simple mathematical mistake could cause disastrous consequences. 360 o 120 o = 240 o. c. Determine the magnetic azimuth from your location to the distant known point. There are three base lines true north, magnetic north, and grid north. It is comparable to doing about face. To obtain a back azimuth from an azimuth, add 180degrees if the azimuth is 180 degrees or less, or subtract 180 degrees if the azimuth is 180degrees or more (Figure 6-3). (4) Draw a line along the straightedge away from the known position on the ground toward your position. H=k0w14}slPZHZ:u_-XC]}>2FD8\70}@YC"/QRpP>eEF^fxFh To start, what is your goal? 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). 5 0 obj This listing indicates a grid convergence of 1o 00' 00". True endstream endobj 1782 0 obj <>stream (6) Repeat 3, 4, and 5 for a second position and a third position, if desired. b. HMk@azp*@4X6{ A circle equals 6400 mils divided by 360 degrees, or 17.78 mils per degree. (b) To use a magnetic azimuth in the field with a compass, change the grid azimuth plotted on a map to a magnetic azimuth (Figure 6-14). For mils, if the azimuth is less than 3200mils, add 3200 mils, if the azimuth is more than 3200 mils, subtract 3200 mils. Tipsy Tuesday: Cold Bow Challenge, Gear Reviews, And The Latest Hunting News! To convert a magnetic azimuth to a grid azimuth, subtract the G-M Angle. Why Walden's rule not applicable to small size cations. Determine the grid coordinates to the desired accuracy. Who's going to be the first hunting 'celebrity' or Youtube personality to put their foot down and stop using cellular cameras? The surface location to target direction will therefore be referenced to Grid North. GM Angle= 7W 2. hb```"?f" !E5r|x:s9DvD*\^b"/mKG@@al>;/UbD-m- 1?(RA)@'7$Z4 ER#cJCg((`R``A*x endobj If you have a map and a compass, the one of most interest to you will be between magnetic and grid north. The grid azimuth can now be converted into a magnetic azimuth because the grid azimuth is now larger than the G-M angle. In either case, the listed Declination, or GM Angle on the map (which may or may not be correct due to Magnetic North Pole movement) is for the center of the map, and depending on the whats under or on top of the surface, the Declination degree may be distorted during your trip. On medium-scale maps, the declination information is shown by a note in the map margin. (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). a. exceeds the range of the compass, so 403 degrees cannot be the http://www.outdoorsfather.com/2015/02/map-reading-true-north-magnetic-north-grid-north/, https://www.ngdc.noaa.gov/geomag/img/DeclinationMap_US.png, Magnetic Declination Varies Considerably Across The United States | U.S. Geological Survey, https://www.adkhighpeaksfoundation.org/navagation.php, MTN OPS Merinos, Grid Fleece and Pursuit Vest initial impressions, Ah laddie, is a can of worms this come one come all to the huntin woods. 2296 0 obj <>stream d. Conversion. 260 180= 80 Step 2. The formula used to convert a geodetic azimuth to a grid azimuth includes the convergence angle, and another element. Contact Us, Privacy & Legal Statements | Copyright Information (2) Identify two or three known distant locations on the ground and mark them on the map. (5) Convert the grid azimuth to a back azimuth. Is Grid North the same as magnetic north? correct back azimuth. b. Mil. Direction plays an important role in a soldiers everyday life. CR 98 JORDINATE CON Grid: Add 60 Ok, but your longitude lines on your map dont follow magnetic north/south, depending on your location. WEST IS 270. Declination diagram with arbitrary line. Magnetic declination correction converts azimuth values between the Magnetic North and True North systems. a. Do you add or substance when converting a grid azimuth to magnetic azimuth in the westerly GM angle? relatively), but now the desire is to reverse the travel in order One does not typically work with directions exceeding 360 I don't get why you need to substract your compass value <> Count the number of degrees from the 0-degree mark at the top of the protractor to this north-south grid line and then count the number of degrees from the 180-degree mark at the bottom of the protractor to this same grid line. ( d) To measure an azimuth, turn your entire body toward the object and point the compass cover directly at the object. endstream endobj 1784 0 obj <>stream True North. On a plane surface this would be the shortest distance between two points]. Local values of magnetic declination should be stated in the well program to plus or minus 0.1O. f. The location of the user is where the line crosses the linear feature. When using the map and compass method. c. To obtain an accurate reading with the protractor (to the nearest degree or 10 mils), there are two techniques to check that the base line of the protractor is parallel to a north-south grid line. b. When using the straightedge method (Figure 6-19). (3) Measure the magnetic azimuth to one of the known positions from your location using a compass. If you know who Lars Ulrich is, you can convert your azimuths. % WebAdd the GM angle to convert a magnetic azimuth into a grid azimuth. The azimuth, 260, is more than 180, so subtract 180 from the azimuth. How do you convert magnetic bearings to grid bearings? You can bypass all the calculations by purchasing a compass that allows you to set your declination. There are 180 140 = 40 degrees between the South and the point, therefore the quadrant bearing is S40E. When using an azimuth, the point from which the azimuth originates is the center of an imaginary circle . It is an arc, indicated by a dashed line, that connects the grid-north and magnetic-north prongs. A method of locating or plotting an unknown position from a known point by giving a direction and a distance along that direction line is called polar coordinates. endobj %%EOF (f) The inclusion of the true-north prong in relationship to the conversion is of little importance. Apply the mathematical formula to convert a magnetic azimuth to a grid azimuth. The user should be able to determine whether the initial azimuth reading was correct. WebIn this example, the known azimuth is 270 magnetic. Once the degree is in the center of the indicator, youre set. c. Grid Convergence. (7) The location of the unknown position is where the lines cross on the map. You will find that every zone in a State Plane coordinate system has a central meridian. (1) Orient the map on a flat surface by the terrain association method. Being in the right place at the prescribed time is necessary to successfully accomplish military missions. GN 4 3 1. Grid Correction Angle. Since 0 degree is the same as 360 degrees, then 2 degrees is the same as 362 degrees. One note provides instructions for converting magnetic azimuth to grid azimuth; the other, for converting grid azimuth to magnetic azimuth. 1778 0 obj <> endobj On the Earth they are not parallel with each other. Resection with map and compass. (5) Repeat 3 and 4 using a second known position. 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. xUMo1+1vmR6!j?__wrVxuzsei8Vmq.a+Qgl_9lz(A#l$ fQUzp6`Y+F,aeBBa[[c ^`;x1zKEyH9 NYtK,|m7-oF=HI)''UG~PycHNu-3r+|Q!vmR0T KiU)QHc|j'szMV+: s BH4/&`N3qgTR--H\Bg,R7d,B)th|1u"Uf0#bOzM&Z6fFmtQcX825Qb-Kyu ,F!bW\{JI6=aGc9MX'z_R0K}y%!> With this in mind, the following procedure is suggested: True North azimuth will equal 90; Magnetic azimuth will equal 90 plus/minus declination; Grid azimuth will equal 90 plus/minus grid convergence. Your Draw an arrow for Magnetic North using an exaggerated angle east or west of True North showing the declination angle (east declination is east of True North and west is west). compass. endstream endobj 1779 0 obj <>/Metadata 85 0 R/Pages 1776 0 R/StructTreeRoot 113 0 R/Type/Catalog>> endobj 1780 0 obj <>/MediaBox[0 0 612 792]/Parent 1776 0 R/Resources<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI]>>/Rotate 0/StructParents 0/Tabs/S/Type/Page>> endobj 1781 0 obj <>stream Save my name, email, and website in this browser for the next time I comment. Alaska is more from what I recall. yg! $RC ku,B:d k5(*(ig0;5o!` QuM^4oG-9Q[bG}1g_iulBewm|J""F]||0 WebConverting azimuths to quadrant bearings or vice versa is easy. (b) To use a magnetic azimuth in the field with a compass, first change the grid azimuth plotted on a map to a magnetic azimuth (Figure 6-11). The answer is that you can use a compass or an app like Google Maps on your phone to find out the grid azimuth. xUM0#hWgK G!(l9Rq[L1yfzYjz`W^7]>o_vz{a}Kt;8X 9ngA>A))(&J%qWI H-5dEC{,O^fa< nY&j!5bA w}C|3nq{ceUxc0P }*%9M4.e$$""U rQ1md6G+ a :mB>8a/7Z's?9hd-VyH"a.9QEhd?SGq9~*OO.fM&:CEY) a. Then, what exactly is a grid azimuth? You need to know that if your declination is East, it means that Magnetic North is East of your location. If the two counts are equal, the protractor is properly aligned. To convert this UTM Grid North direction to a True North direction, you must apply the grid convergence to the calculated UTM Grid North direction. A,wA;n@u"AVlwE;R;#\ci=p~58sq+%kc They are certainly not parallel with one another and certainly not parallel with the central meridian. Going from the While the relative positions of the prongs are correct, they are seldom plotted to scale. Converting to a magnetic azimuth when the G-M angle is greater. : The University of Akron, Ohio To determine your GAZ, you should use one of these, known as a protractor. 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 the maps grid, place a small tick mark in the center of the protractor (they usually have a hole for that purpose), and use some sort of straight edge to line up the center point and the azimuth (use the INNER RING of degrees, not the outer ring), place a tick mark, move the protractor out of the way, and draw a straight line from the origin point to the azimuth line. 1 0 obj Remember, there are no negative azimuths on the azimuth circle. Computer programs like GEOMAG use current magnetic models and calculate up-to-date local declination figures. If you are surveying or doing something other than land nav for hunting, this may matter. Web(1) Look at the declination diagram and determine the direction between the line representing grid north and the line representing magnetic north. The College of Earth and Mineral Sciences is committed to making its websites accessible to all users, and welcomes comments or suggestions on access improvements. a. A rule to remember when solving such problems is this: Nomatter where the azimuth line points, the angle to it is always measured clockwise from the reference direction (base line). Hvg dKg|?s::ikP8> The first step to converting magnetic azimuth to grid azimuth is to determine the declination angle. (d) Remove the protractor and draw a line connecting the known point and the mark on the map. More on that in the future. This circle is divided into 360 degrees or 6400 mils . 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. When you say you aligned map and compass north. Draw a magnetic prong from the apex of the grid-north line in the desired direction (Figure 6-9). Webgrid azimuth = (magnetic azimuth + magnetic declination) + grid convergence (#3) To convert from a grid azimuth to a magnetic azimuth substitute from relationship #1 into If youre not using that type of compass, youll always have both Grid and Magnetic Azimuths to deal with when navigating. 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. Your email address will not be published. In the jpg below, you can see the declination window at 6 oclock on the compass, or specifically, at Zero degrees. <> The grid north for a particular map is usually chosen so that it deviates very little from the true north]. 9 0 obj<>>>/MediaBox[0 0 612 792]>> 10 0 obj To convert a grid azimuth to a magnetic azimuth, subtract the G-M angle from the grid azimuth. (2) When working with a map having a west G-M angle: (a) To plot a magnetic azimuth on a map, first convert it to a grid azimuth (Figure 6-13). Underneath the compass is a small standard screw slot that an accompanying tool will adjust to whatever your declination is, East or West. The name is derived from Old French or Spanish respectively: rumb or rumbo, a line on the chart which intersects all meridians at the same angle. Where the base line intersects the horizontal line, between 90 and 270 degrees, is the index or center of the protractor (Figure 6-6). The index mark is the center of the protractor circle from which all directions are measured. All the norths are parallel in the plane systems; this is, of course, unrealistic. What is the Grid Azimuth? The site editor may also be contacted with questions or comments about this Open Educational Resource. I'll be doing it. Using LARS, convert to a grid azimuth. &n7n_n mI6C. 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. When working with the UTM system, the calculated direction between two UTM coordinates is referenced to Grid North. (5) Draw a line on the map from your position on this grid azimuth. 8 0 obj An arc indicated by a dashed line connects the prongs for true north and grid north. No mathematical equation is necessary because the compass itself has the declination already accounted for by your adjustment. The mil expresses the size of an angle formed when a circle is divided into 6,400 angles, with the vertex of the angles at the center of the circle. Thus we ADD the variation (12 degrees) to give the Grid Bearing [A rhumb line appears as a straight line on a Mercator projection map.

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