Project Server 2010 to 2013 upgrade

Hi All,

I have the read the technet article for Project Server 2010 to 2013 upgrade. It is mentioned that we need to setup Project Server 2013 environment before starting the migration process.  It means, in the new server do we need to only install SharePoint and Project Server 2013. OR we need to create the SharePoint web application and create a new Project Server instance under the web application and start the migration process. 

https://technet.microsoft.com/en-us/library/ee662496.aspx

Thanks in advance, Taj