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+====== Calibrate a map ======
+Before a map can be used in QV, it must be georeferenced or "calibrated". This requires the identification of the map type and its reference system and the assignment of specific points to known coordinates. This is essential in order to georeference the map, i.e. to enable QV to transfer map coordinates to screen coordinates and vice versa.
+So, in order to use a map in QV which is located as a bitmap on your PC harddisk (for example a scanned map), three steps are required.
+===== 1. Import the map =====
+So, first of all, import the map as described in the chapter [[en:35_maps:d_import|Import new map]]. Thereafter, you will find the map in the X-Plorer with the remark **Not calibrated**:
+{{:en:35_maps:xplorer_unkalibriert_en.png|}}
+===== 2. Open the map =====
+In the next step, open the map in the 2D mode by clicking the icon **Show in map** {{:images:bm69.png|}}.
+As the map ist still not calibrated, QV will indicate in the bottom line the positions as pixel coordinates. The coordinates of the mouse pointer ar indicated in //black//, those of the map cursor in //magenta//.
+{{:en:35_maps:mapwin_unkalibriert_en.jpg?450|}}
+===== 3. Calibrate the map =====
+Open the calibrating assistant by selecting **File > Calibrate map...** from the main menu.
+{{:en:35_maps:frmassicalibration_1_en.png|}}
+In the first page you can enter some general information like **Name**, **Scale**, **Map number** and additional **Info**.
+Then, click **Continue** to enter the map projektion.
+==== Specifying the projection ====
+{{:en:35_maps:frmassicalibration_2a_en.png|}}
+According to the selection made, specific options may appeaar at the button of this window.
+=== Latitudes - Longitudes ===
+This is the simpliest mode which you should choose, if
+  * The exact projection of the map is unknown
+  * The grid of the map is only slightly curved or not curved
+  * The grid is labeled with longitudes and latitudes
+=== UTM ===
+This is the right selection for maps with a UTM grid.
+You will have to specify the UTM zone and the hemisphere.
+{{:en:35_maps:frmassicalibration_2b_en.png|}}
+=== National Meter Grids ===
+For this option you have to choose the adequate grid system from the list.
+{{:en:35_maps:frmassicalibration_2c_en.png|}}
+=== Projection ===
+For this option you must know the exact projection of the map, including all relevant parameters.
+{{:en:35_maps:frmassicalibration_2d_en.png|}}
+So, choose the projection from the list and enter the required parameters into the corresponding fields.
+==== Entering the reference points ====
+On the third page of the assistant, you will have to specify the refernece point for the calibration.
+{{:en:35_maps:frmassicalibration_3o_en.png|}}
+In order to make this as efficient as possible (enter as many points as necessary but not more than essential), various patterns are available.
+| 3x3 | See graphic above\\ This pattern is sufficient in case the map grid is only slightly curved, and 9 intersections of 3 latitudes and 3 longitudes are available. \\ So you have to define a total of 9 points in the map but only have to enter 3 coordinate values. |
+| 2x2 | {{:en:35_maps:frmassicalibration_3a_en.png|}}\\ This pattern is adequate if the map grid is not curved and four intersections of 2 latitudes and 2 longitudes are available. \\ So you have to define a total of 4 points in the map but only have to enter 2 coordinate values. \\ For the projections //UTM// and //National Meter Grid//, only this layout is available. |
+| 3-4 | {{:en:35_maps:frmassicalibration_3b_en.png|}} \\ This layout has primarily been implemented for the mode //projektion//, where 3 points are usually enough. |
+| 3-9 | {{:en:35_maps:frmassicalibration_3c_en.png|}} \\ Using this option, you can enter up to 9 points. |
+=== Functions of a reference point ===
+The status iof a reference point is indicated by colors:
+| {{:de:35_maps:calpoint_1.png|}} | Still no coordinate entered, still no point in the map defined. |
+| {{:de:35_maps:calpoint_4.png|}} | Still no coordinate entered but point in the map already defined. |
+| {{:de:35_maps:calpoint_2.png|}} | Valid coordinate entered but still no point in the map defined. |
+| {{:de:35_maps:calpoint_3.png|}} | coordinate entered and point in the map defined. |
+To enter a point in the map, first click the corresponding button, e.g. {{:de:35_maps:calpoint_5.png|}} and the click on the corresponding point in the map. A red mark will then appear at this point of the map: \\
+{{:de:35_maps:calpoint_7.png|}} \\
+As confiramtion, the corresponding button in the assistant will switch to //green//.
+Thereafter, please enter the geographic coordinate. You must enter the value in the the units which are selected under **Units**. Thereafter, the entry field will also switch to //green//.
+Additionally, the **P**x icons have a drop-down menu: {{:en:35_maps:calpoint_6_en.png|}}
+|Show point in map | Moves the map in order to display this point. |
+|Copy geo-coordinate from a calibrated map | Using this function, you can copy the coordinate which you have to enter from a map which has already been calibrated. |
+|Enter pixel coordinate manually | Through this option, you can enter the X and Y coordinates in pixel units in the corresponding box. |
+|Delete point | This will delete the point definition, so that te status switches back to orange. |
+==== Save calibration ====
+After all points are defined, i.e. all fields indicate the status in //green//, click the **Save** button.
+Thereafter, the calibration will be saved, the calibration status updated in the map list and the map will be displayed. So you can control immediately, if the calibration is correct.
+If the software switch "Keep dialog open" is set, the assistant will not be closed, so you can make further corrections if required. Otherwise the assistant will automatically close.
+Of course you can restart the assistant at any time in order to check or to modify the map calibration.
+^ It is important to check the calibration! Follow the latitudes and longitudes with the mouse pointer and watch the coordinates which are specified in the status line. If they are not plausible, repeat the calibration.\\ Another test: Double click on a map point which is not close to a calibration point and save this point as a waypoint. Plot this waypoint in the map and check whether the mark is in the same place. If you have GPS tracklogs from this area, plot them in the map and check for their correct placement. ^

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