# Azimuth angle results are different for 'Field Calculator' and 'Measure Angle' on QGIS

I measured the angle between two lines with Measure Angle. The result is 39.531°. In attribute table I used this script for calculating azimuth with Field Calculator:

``````degrees(azimuth(start_point(\$geometry), end_point(\$geometry)))
``````

The result of Field Calculator is 46.62005°. Why are there different results?  Coordinates: Latitude1: 39.0390110 Longitude1: 33.8493433 Latitude2: 39.0413637 Longitude2: 33.8518330

• Probably the two tools are using different CRS's. Check the description of the Azimuth function to see what CRS it uses (probably the layer's CRS). Check the Project Properties settings to see what CRS the measure tool uses. – csk Dec 22 '19 at 17:59
• I also thought about this, I set the CRS to 4326 - WGS84 for layer and project. The result is the same. I don't know if one tool uses grad angle unit. The description: Returns the north-based azimuth as the angle in radians measured clockwise from the vertical on point_a to point_b. – Edip Ahmet Dec 22 '19 at 18:02
• @EdipAhmet setting a CRS for a layer is bound to errors if transform is what you need! what is the datas initially defined CRS? 7 degrees is quite a reasonable margin of error if one method is getting the 'north' reference by math, and the second by drawing, and the CRS is based on e.g. different ellipsoids. – ThingumaBob Dec 22 '19 at 19:33
• I guess 7 degrees error is the difference between true north and north. – zlikotp Dec 22 '19 at 23:47
• Yes I also suspected this. I am a surveyor and we use bearing. I couldn't find any answer for calculation of bearing. The line is 160 meters, I think there shouldn't be a big difference like 7 degrees with true north and rectangular north. I will try projected crs like 3 or 6 zone UTM. I will upload the project here. – Edip Ahmet Dec 23 '19 at 16:07