Originally Written by Michael Hompus - https://gallery.technet.microsoft.com/scriptcenter/ConvertFrom-SiteMap-25e17f82

Convert-FromSitemap.ps1

<#
.SYNOPSIS
    Returns all URLs and optional metadata from an XML Sitemap
.DESCRIPTION
    Downloads an XML Sitemap and parses the content to retrieve all the information. If the file contains Sitemap Index entries those links will be followed as well.
.NOTES
    Author: Michaël Hompus
    License: This work is licensed under a Creative Commons Attribution-ShareAlike 2.5 Generic License.
.PARAMETER Url
    The URL for a XML Sitemap file
.PARAMETER NoFollow
    Indicates any Sitemap Index entries won't be followed
.LINK
    Invoke-RestMethod
    https://gist.github.com/eNeRGy164/a644417b737eb5d3af3c80d4ceb527e1
.EXAMPLE
    ConvertFrom-SiteMap.ps1 -Url https://blog.hompus.nl/sitemap.xml
.EXAMPLE
    ConvertFrom-SiteMap.ps1 -Url https://blog.hompus.nl/sitemap.xml -NoFollow
#>
[CmdletBinding()]
param(
    [parameter(Mandatory = $true, HelpMessage = "The URL for a XML Sitemap file")]
    [string]$Url,

    [parameter(HelpMessage = "Indicates any Sitemap Index entries won't be followed")]
    [switch]$NoFollow
)

Function ParseSitemap($url) {
    Write-Verbose "Fetching file from $url"
    $sitemap = Invoke-RestMethod $url -UseBasicParsing

    Write-Verbose "Parsing sitemap"
    if ($sitemap.sitemapindex -ne $null -and !$NoFollow) {
        Write-Verbose "Following sitemapindex entries"
        $sitemap.sitemapindex.sitemap.loc | ForEach-Object { 
            ParseSitemap -url $_
        }
    }

    if ($sitemap.urlset -ne $null) {
        Write-Verbose "Parsing urlset"
        $sitemap.urlset.url
    }
}
$result = ParseSitemap('https://www.sheldonhull.com/sitemap.xml')
$result  | Export-Csv -path C:\temp\CSV-CurrentSitemap.csv -NoTypeInformation -Encoding UTF8