A feature of determining directions on a topographic map is the presence of a coordinate grid on it, the vertical axes of which do not coincide with the direction to the north. The direction to the north shows only the axial meridian of the zone and the vertical borders of the map.
Determining directions on land using a topographic map, using paper topographic maps on a camping trip, preparing maps, orienting maps on the ground.
The initial directions on the topographic map are the directions of the geographical meridian, magnetic meridian and axial meridian. Relative to these directions, orienting angles are formed. Orientation angles include true azimuth or bearing, magnetic azimuth and directional angle.
True azimuth of IA or bearing.
The true azimuth of an IA or bearing to an object is the horizontal angle between the northern part of the true meridian (northward direction) and the direction from the observation point to the object, measured clockwise.
Magnetic azimuth MA.
This is the horizontal angle between the northern part of the magnetic meridian and the direction of the object, measured clockwise. To orient the directions to any object on the map, use the directional angle a.
Directional angle a.
This is the horizontal angle between the north direction of the vertical grid line on the map and the directions to the object, measured clockwise. Using this angle allows you to more accurately determine the direction to the desired object. The orientation of the lines along the magnetic meridian is rougher, and the use of azimuths is inconvenient, since the azimuths of the same line at different points are different.
Transition from directional angles and true azimuths measured on a map to magnetic azimuth.
It is performed according to the formulas taking into account the sign of the magnitude of the magnetic declination and the approach of the meridians: MA = IA Sk and MA = a Sk Sat, where Sk is the magnetic declination; Sat rapprochement of meridians. Data on the magnetic declination, the convergence of the meridians are placed under the southern side of the frame of each sheet of the topographic map.
The use of paper topographic maps in the campaign, the preparation of topographic maps for the campaign.
We believe that you have finally selected a route and selected paper topographic maps for it. The route was drawn on the map. Along the way, determine the number of the coordinate zone in which the route runs. It can be determined by the horizontal coordinate, if it is on the map. The first digit or the first two at the horizontal coordinate is the zone number. The most difficult case is when your GPS-navigator does not have a map of the required area. Then, to plot the current trajectory or its individual points on the map according to the GPS-navigator, it is necessary to digitize the coordinate lines of the map.
If you take an atlas that has a kilometer-long grid, then you must manually digitize it. To do this, it is enough to roughly determine the coordinates of at least one point to find the corresponding square. If there are no other ways, then you can refer to the overview map on the first page of the atlas, where there is at least one meridian and one parallel. To transfer from longitude / latitude, you can use the same device, temporarily switching it to the display of coordinates in degrees, entering a new waypoint with the given coordinates, and then restore the setting. If you are going to print cards on a printer, it is most reasonable to do this from the OziExplorer program by setting up the grid.
Go to Grid Line Setup »Other Grid, turn on the Grid On icon, turn off Auto Scale. In the Line Interval box, put No Grid, if the desired grid is already on the map, in the opposite case, set the value so that the lines go through 2 centimeters, for example, put 4 kilometers for a scale of 1: 200,000. Set the Label Interval parameter in the same way, even if you set No Grid. This will ensure digitization at the edges of the map. When navigating near the border of the zone, it is useful to turn off Clip to Near Line, then the constructed mesh will not end at the border of the zone. Remember that all this makes sense when the coordinate system is configured on the SK-42 (Pulkovo 1942).
When printing maps on a printer, it is convenient to adjust the size of the program window so that it displays the desired fragment of the map that fits on one sheet, if necessary, change the display scale, and when printing set the Window »to Scale option. In this case, it is possible to more flexibly control the distribution of fragments across the sheets, and the digitization will be on all sheets, and not just the extreme ones. Do not forget that color inkjet printers are afraid of water, so that printed paper cards must be placed in sealed bags or laminated.
Orientation of a topographic map in the area.
Finally came that exciting moment when you are on the ground with a map in one hand and a GPS navigator in the other. The first thing that needs to be done is to map your location, standing point. If the map is digitized and you have a navigator, then a standing point is marked by the coordinates measured by it. The case in the absence of a GPS navigator will be discussed below. Then you need to orient the map, that is, place the map in a horizontal plane so that the upper side of the frame faces north. Then the location of local objects and relief will correspond to the conventional signs on the map. You can orient the map in the following ways.
Towards the landmark.
A linear landmark is an extended landmark such as a road or a clearing. We rotate the map so that the direction of the linear landmark shown on the map coincides with the real direction on the ground. Then we verify the location of local objects and landforms in relation to a linear landmark with those shown on the map. Given their location, orientation can be considered correct. With the method in the direction to the landmark, the direction from the point of standing to any local local object that is reliably identified on the ground and on the map is selected. Then we turn the map, achieving the coincidence of directions on the map and the terrain.
Orientation of the map by compass is the most universal and convenient, since it is more accurate and can also be used when its location is unknown. With approximate orientation using the compass, the north direction is determined, then the map is rotated until the upper side of the frame is perpendicular to the north direction. More accurate orientation is applied if the directional correction from declination is more than 3 degrees. First, the compass reference indicator is set against the division of the scale equal to the correction direction. If the directional correction is positive, then the reference pointer is set to the right of the zero division of the scale, and if negative – to the left.
Then the compass is installed on the map so that the zero diameter of its limb coincides with one of the vertical lines of the grid. Without changing the position of the compass, the map is rotated until the north end of the magnetic needle is opposite the reference that was previously set on the scale.
Setting the geodetic coordinate system (datum) in the GPS navigator.
To set the coordinate system SK-42 (Pulkovo 1942), select the user system (user datum) in the Datum setup menu:
1. Install SETUP – UNITS – MAP DATUM – USER.
2. Enter the following parameters: dX = 28; dY = -130; dZ = -95; dA = -108; dF = 0.00480795.
To display the coordinates in the kilometer grid.
1. Install SETUP – UNITS – POSITION FORMAT – USER GRID.
2. Enter the following parameters:
Latitude Origin longitude of the central meridian, for example, for Moscow W39 degrees, St. Petersburg W33 degrees; Scale Factor = 1.0; False Easting = 500000, False Northing = 0. All values indicating distances are given in meters.
Based on materials from the book All About GPS Navigators.
Naiman V.S., Samoilov A.E., Ilyin N.R., Sheinis A.I..