Custom visual height on iPad

[matemusic]

Hello,

I am facing with a problem, for which I have been searching a solution for a couple of hours, but I didn't find any. 

I need to know height of custom visual, so I am using code below. 

public update(options: VisualUpdateOptions) {
//....some other code
     let height: number = options.viewport.height;
//some other code....

It is working OK on Chrome browser, but when I test it on iPad app, I get strange results. Sometimes height value is little to big (often when I open app), sometimes value is OK (when I refresh app).

Can anyone know, what is causing this problem? Do I have to use a different code for getting a height or different placement? Or do I have to include somewhat code, which refresh height?

Thank you!