Powershell update all navigation URL to be relative instead of absolete

I have used this powershell script to update all navigation items in a site collection to use only relative URLs instead of absolute ones.

function ProcessWeb($currentWeb)

{ 

   Write-Host -ForegroundColor Green "Processing web" $currentWeb.Url

   $currentWeb.AllowUnsafeUpdates = 1

   UpdateNavigation($currentWeb)

   $currentWeb.Update()

   $currentWeb.AllowUnsafeUpdates = 0

   foreach($sub in $currentWeb.Webs)

   {

         ProcessWeb($sub)

   }       

}

function UpdateNavigation($web)

{

   

    $topNavigationNodes = $web.Navigation.TopNavigationBar

    UpdateNavNodes($topNavigationNodes);

    $quickLaunchNodes = $web.Navigation.QuickLaunch

    UpdateNavNodes($quickLaunchNodes);

}

function UpdateNavNodes($navNodesCollection)

{

  if ($navNodesCollection -ne $null)

  {

    foreach($navNode in $navNodesCollection)

    {

        $navNode.Url = $navNode.Url.Replace('http://<My Root Site Url>','')

        $navNode.Update()

    }

  }

}

Write-Host -ForegroundColor red "STARTED"

ProcessWeb(Get-SPWeb -identity "http://<My Site Collection Url>")

Write-Host -ForegroundColor red "FINISHED"