web map scale does not match map scale on ArcGIS Pro

[AllenHuang]

Hi 

I have been working on a web map project where map accuracy is essential for legal purposes. At the end of my development, I discovered that the web map scale is inconsistent with ArcGIS Pro. 

What would be the best approach to tackle this problem?

Allen

[AllenHuang · Accepted solution]

The reason my web map was matching the map scale on ArcGIS Pro was because they are in different Spatial references. The web map is in arcgis web mercator and my ArcGIS Pro was set to my local coordinate system.

Change the spectialReference parameter in the map view will correct put the web map to the correct scale.  

[vg11]

I'm sorry if the answer is obvious, but did you change your coordinate system in Pro or Map Viewer? I am having the same issue and haven't determined a way to fix this. Any walk thru or information is greatly appreciated. My current coordinate system in Pro is, XY: NAD 1983 Texas N Central, Z: Unknown VCS from ArcInfo Workstation. 

[AllenHuang]

Hi vg11

Just to clarify a little. When I say map view, I am referring to `esri/views/MapView` module/class from the ArcGIS javascript library. But the solution should work on both Pro and Web Map.

In ArcGIS Pro, you would redefine the coordinate system in your map project if it hasn't already adopted the coordinate system of the first layer or basemap you started your project with. In Javascript, your would define the spatial reference when create your map object.

 However, with javascript, it a bit tricky since if you specify a particular spatial reference on your map object. Other maps layers in different coordinate system do not gets auto-projected, at least in my experience. You would either be unable to add the map layers, or it will rendered incorrectly.