Why does not equal length of line in DIRECTION/LENGTH with length of line in MEASURING in OpenLayers 2.13?

Question

My map projection is: "EPSG:900913", display projection is "EPSG:4326" and units is "m", however does not equal the length in Direction/length with the length is calculated in measuring in OpenLayers, in fact OpenLayers show the length more than the actual length when I use measure control. I've set the option geodesic: true to my measure control.

For example:

the enter length is: 100m

the length after measuring is: 85.29m

Define measure control:

 measureLine = new OpenLayers.Control.DynamicMeasure(OpenLayers.Handler.Path);
measureLine.geodesic = true;

function insertDirectionLength(drawType) {
    var values = parseInput(
    window.prompt(
            "Enter direction and length offset values for new point (e.g. '-45, 10')", "direction, length"
    )
     );
     if (values != null) {
         var controlKey,key;
         for (key in controls) {
             controlKey = controls[key];
             if (drawType == key) {
                  controlKey.insertDirectionLength(values[0], values[1]);
             } 
         }
     }
 }

How to resolve this problem?

You're using Mercator for length and comparing with great circle on a sphere? — Vince, Oct 25 '15 at 22:31
Similar to http://gis.stackexchange.com/questions/48142/which-area-measurement-to-trust-the-same-polygon-in-googleearth-v-arcgis (which is itself a duplicate) — Vince, Oct 25 '15 at 22:32
If you edit the question to contain the exact vales used (lon,lat in addition to bearing and distance), and the exact coordinate values of the resuling geometry, you might find that the issue is the same. — Vince, Oct 27 '15 at 10:57
Every time someone says EPSG:900913 it makes @mkennedy eyes twitch. Please use code EPSG:3857 instead. — Mintx, Jan 08 '16 at 14:46

score 0 · Answer 1 · answered Jan 12 '16 at 16:03

My map projection is: "EPSG:900913" ,Display projection is "EPSG:4326"

I believe this is the crux of your problem. It looks like you are drawing in ~~EPSG:900913~~ EPSG:3857 and you are measuring in EPSG:4326.

The Pseudo-Mercator projection is notoriously bad at calculating/drawing distances, so I would not use this projection for that kind of work.

Why does not equal length of line in DIRECTION/LENGTH with length of line in MEASURING in OpenLayers 2.13?

1 Answers1

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