Databases
StackOverflow2013
Postsdbo
POCalculate bearing between two locations (lat, long)
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POCalculate bearing between two locations (lat, long)
    primarykey
    data
    text
    <p>I'm trying to develop my own augmented reality engine.</p> <p>Searching on internet, I've found this useful <a href="http://www.invasivecode.com/blog/archives/1435" rel="noreferrer">tutorial</a>. Reading it I see that the important thing is bearing between user location, point location and north.</p> <p>The following picture is from that tutorial.</p> <p><img src="https://i.stack.imgur.com/rKr0w.jpg" alt="enter image description here"></p> <p>Following it, I wrote an Objective-C method to obtain beta:</p> <pre><code>+ (float) calculateBetaFrom:(CLLocationCoordinate2D)user to:(CLLocationCoordinate2D)destination { double beta = 0; double a, b = 0; a = destination.latitude - user.latitude; b = destination.longitude - user.longitude; beta = atan2(a, b) * 180.0 / M_PI; if (beta &lt; 0.0) beta += 360.0; else if (beta &gt; 360.0) beta -= 360; return beta; } </code></pre> <p>But, when I try it, it doesn't work very well.</p> <p>So, I checked iPhone AR Toolkit, to see how it works (I've been working with this toolkit, but it is so big for me).</p> <p>And, in <a href="https://github.com/nielswh/iPhone-AR-Toolkit/blob/master/ARKit/ARGeoCoordinate.m" rel="noreferrer">ARGeoCoordinate.m</a> there is another implementation of how to obtain beta:</p> <pre><code>- (float)angleFromCoordinate:(CLLocationCoordinate2D)first toCoordinate:(CLLocationCoordinate2D)second { float longitudinalDifference = second.longitude - first.longitude; float latitudinalDifference = second.latitude - first.latitude; float possibleAzimuth = (M_PI * .5f) - atan(latitudinalDifference / longitudinalDifference); if (longitudinalDifference &gt; 0) return possibleAzimuth; else if (longitudinalDifference &lt; 0) return possibleAzimuth + M_PI; else if (latitudinalDifference &lt; 0) return M_PI; return 0.0f; } </code></pre> <p>It uses this formula:</p> <pre><code>float possibleAzimuth = (M_PI * .5f) - atan(latitudinalDifference / longitudinalDifference); </code></pre> <p>Why is (M_PI * .5f) in this formula? I don't understand it.</p> <p>And continue searching, I've found another <a href="http://www.movable-type.co.uk/scripts/latlong.html" rel="noreferrer">page</a> talking about how to calculate distance and bearing of 2 locations. In this page there is another implementation:</p> <pre><code>/** * Returns the (initial) bearing from this point to the supplied point, in degrees * see http://williams.best.vwh.net/avform.htm#Crs * * @param {LatLon} point: Latitude/longitude of destination point * @returns {Number} Initial bearing in degrees from North */ LatLon.prototype.bearingTo = function(point) { var lat1 = this._lat.toRad(), lat2 = point._lat.toRad(); var dLon = (point._lon-this._lon).toRad(); var y = Math.sin(dLon) * Math.cos(lat2); var x = Math.cos(lat1)*Math.sin(lat2) - Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon); var brng = Math.atan2(y, x); return (brng.toDeg()+360) % 360; } </code></pre> <p>Which one is the right one?</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USVansFannel
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POCalculate bearing between two locations (lat, long)
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POCalculate bearing between two locations (lat, long)
      1. USCraigy
      1. VTFavorite
    3. VO
      singulars
      1. POCalculate bearing between two locations (lat, long)
      1. This table or related slice is empty.
      1. VTUpMod
    1. CODid you ever resolve this issue? I am interested in which solution you went with
      singulars
      1. POCalculate bearing between two locations (lat, long)
      1. USCraigy
    2. COYes, I have to add my own answer shortly.
      singulars
      1. POCalculate bearing between two locations (lat, long)
      1. USVansFannel
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload