Scale bar wrong after zoom or pan

Question

Hello,

Has anyone seen the problem where the scalebar becomes incorrect after a zoom or pan? When the map initially loads the scale looks about right. When I zoom in or pan, the scale bar refreshes with the wrong scale, eg it goes from measuring 0.3 km to 100km after zooming.

See the before and after shots attached.

BadScale2.JPG

BadScale1.JPG

calculate.png

integer.png

jcarlson_1-1619548826193.png

2024-11-15_13-28-12.png

Anonymous User · Answer

Original User: Jian

Mark,

You are right. The scalebar read map unit from the first layer. The next version will read it from the map.spatialReference to determine if this is a projected coordinate system, then decide the unit. Another words, you don't have to specify the unit for your WMS layer. However, I would still encourage to set the correct unit for your layer for the reason of completeness.
Thanks.

MarkDonnelly · Answer

Note that the scalebar units are taken from the layer with the zero index, so the fix only applies to that layer.

ie the map layer that is the first to be added to the map or if as in the previous example, the layer is added to index 0. The layer could also be moved to index 0 as well and that would affect calculations.

Regards,

Mark

MarkDonnelly · Answer

After chasing numerous red herrings I have found the solution:

When I load the WMS layer the 'units' property is not defined by default. This causes the api scale bar calculations to get pretty confused and come up with the wrong numbers on the scale bar.

To get around this I had to manually define the WMS layer 'units' property as 'esriMeters':
wmsLayer.units = "esriMeters";
map.addLayer(wmsLayer,0);

I guess this could be caused by any layer that does not have it's 'units' property defined by default. I hope this helps other people who come across this problem.

Regards,

Mark