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manual:user_guide:maps_tools:offset:example

## Map Offset Procedure Example

13/01/2012 by Richard Lhotsky

### Procedure

• Save a Google Satellite Map crop of a place in China (or wherever else where the satellite does not match the map) from some map-downloading software in Locus Map folder
• Launch Locus Map
• Select an online OSM (OpenStreet) map of the same place and find some distinct point, e.g. a junction
• Save it as a Point of Interest “A” with a clear label saying which map it is from
• Open the saved Google Satellite Map and find the same junction
• Save it again as a clearly named POI “B”
• Measure rectangular distances between these points, i.e. in X,Y axes - most easily with the Guiding function or the Add new track and measuring fn. It displays the distance and azimuth. Then the angles and cardinal directions are calculated
• Tap Menu > More functions > Map offset and set the offsets

### Example

Point A is correct, point B is incorrect. Point B is at a distance of 483 m from the point A in the azimuth of 118 degrees. We have to shift in rectangular ways according to longitude and latitude. Point A is therefore on the upper left, the point B on the lower right. Shift the Google map so that the the points overlay each other, i.e. northward and westward. When the azimuth is 118 degrees let's deduct the parallel (90 degrees) and we have 28 degrees at the point B. Total of angles in a triangle is 180°, we have a right angle 90° and calculated 28°. Remaining angle is 180 – 90 – 28 = 62°. For the shift to the North/South calculate the distance like this: distance = sinus of the B point angle x distance of the points, i.e. sin 28° x 483 = 226 m.

Put -226 into the North field (we are shifting the map southward) and 426 into the East field. Confirm and see that the points overlay each other. 