topic Re: How to find angle between 3 points in Qt Maps SDK Questions https://community.esri.com/t5/qt-maps-sdk-questions/how-to-find-angle-between-3-points/m-p/371160#M1851 <HTML><HEAD></HEAD><BODY><P>a programming language agnostic definition would be</P><P>take 3 sequential points&nbsp; p0, p1, p2, subtract their coordinates and determine their respective angles, then derive the differences</P><P>&nbsp; &nbsp; (d1_x, d1_y) = d1 = p0 - p1&nbsp; yields the differences in the x and y coordinates<BR />&nbsp; &nbsp; (d2_x, d2_y) = d2 = p2 - p1&nbsp; ditto<BR />&nbsp;&nbsp;&nbsp; ang1 = arctan2(d1_y, d1_x)&nbsp; (d1's y, and x differences)<BR />&nbsp;&nbsp;&nbsp; ang2 =arctan2(d2_y, d2_x)<BR />&nbsp;&nbsp;&nbsp; ang = (ang2 - ang1)</P><P>&nbsp; &nbsp; ang_deg = degrees(ang) &nbsp;&nbsp; to convert from radians to degrees if needed</P><P>note you need your language's implementation of arctan2 not atan and that most use arctan(dy, dx) unlike spreadsheets which reverse these.&nbsp; This avoids messy uses of arccos and dot products as normally shown in textbook equations</P></BODY></HTML> Tue, 19 Mar 2019 10:00:13 GMT DanPatterson_Retired 2019-03-19T10:00:13Z How to find angle between 3 points https://community.esri.com/t5/qt-maps-sdk-questions/how-to-find-angle-between-3-points/m-p/371159#M1850 <HTML><HEAD></HEAD><BODY><P>Can you please tell us how to find angle between 3 points</P></BODY></HTML> Tue, 19 Mar 2019 06:50:49 GMT https://community.esri.com/t5/qt-maps-sdk-questions/how-to-find-angle-between-3-points/m-p/371159#M1850 Girishchandra_Yendargaye 2019-03-19T06:50:49Z Re: How to find angle between 3 points https://community.esri.com/t5/qt-maps-sdk-questions/how-to-find-angle-between-3-points/m-p/371160#M1851 <HTML><HEAD></HEAD><BODY><P>a programming language agnostic definition would be</P><P>take 3 sequential points&nbsp; p0, p1, p2, subtract their coordinates and determine their respective angles, then derive the differences</P><P>&nbsp; &nbsp; (d1_x, d1_y) = d1 = p0 - p1&nbsp; yields the differences in the x and y coordinates<BR />&nbsp; &nbsp; (d2_x, d2_y) = d2 = p2 - p1&nbsp; ditto<BR />&nbsp;&nbsp;&nbsp; ang1 = arctan2(d1_y, d1_x)&nbsp; (d1's y, and x differences)<BR />&nbsp;&nbsp;&nbsp; ang2 =arctan2(d2_y, d2_x)<BR />&nbsp;&nbsp;&nbsp; ang = (ang2 - ang1)</P><P>&nbsp; &nbsp; ang_deg = degrees(ang) &nbsp;&nbsp; to convert from radians to degrees if needed</P><P>note you need your language's implementation of arctan2 not atan and that most use arctan(dy, dx) unlike spreadsheets which reverse these.&nbsp; This avoids messy uses of arccos and dot products as normally shown in textbook equations</P></BODY></HTML> Tue, 19 Mar 2019 10:00:13 GMT https://community.esri.com/t5/qt-maps-sdk-questions/how-to-find-angle-between-3-points/m-p/371160#M1851 DanPatterson_Retired 2019-03-19T10:00:13Z