GMap.NET | NET Windows Forms & Presentation is an excellent open source | DevOps library

I have checked the source code, starting from line 1740 until 1748, it turns out that the very _core._position is the one being updated instead of the GMapControl.Position during MouseWheel Zooming. which means that the UI control itself does not know that the position was been changed apparently.

here's the pull request I have made, hopefully, it gets by the owner. I have just replaced the _core._position to Position.

I'm not sure if there's a better way around this but here's a hacky workaround to stop the WM_MOUSEWHEEL message from reaching the control and still execute the zooming logic.

Add the following class to your project:

You will need to create a custom GMapMarker and use the zoom level in the OnRender() to scale the image. Each zoom level has a different ratio but luckily for you, I have mesured them all. Not sure if the ratio changes with different map providers?

You can set the x/y scale and heading using a seperate thread and it will update in real time.

The "defaultZoomLevel" will set the zoom level at which the image has a 1:1 ratio. I have only tried the value 16, not sure it will work for other values you may need to calculate all the ratios for each value or extract the curve from the data and use that to scale the ratio.

Use this to set the zoom level when it changes:

I found the reason for this problem:

I used version 1.7 of this control. After upgrading it to v 2.x (if you use Nuget, you need to uninstall the GMap package, search for the new version and install the new version)

After upgrading, I was able to use OpenStreetMap without any problem.

Try to set the Bitmap image again with the rotation because it is not a reference type:

I had same problem when I went to add custom marker to GMap(scaling width, height, pen size, ...). You can use below code to get GMap.Net Overlayer scale value.