Literature concerning business ecosystems, and digital platforms give an extended range of\nguidelines on how to design a digital platform and transit towards a digital platform business.\nThe literature assumes and already existing knowledge of the business ecosystem, but few gives\nno hands-on recommendations on how to create this knowledge. This thesis proposes a new\nmethod to map a business ecosystem prior to evaluating business platform opportunities. The\nmethod was developed in two steps. Initially a literature survey was conducted to identify\ncommon denominators from the ecosystem and platform literature. This common denominators,\nactor, activity, and asset, where then used as a foundation when the method was developed and\napplied on a Swedish mid-size construction company. The proposed method facilitates these\nthree common denominators and is based on four phases. The method has proved to be able to\ncreate the desired knowledge by, in three workshops, identifying more than 200 entities, and 850\nconnections in the examined ecosystem. The method has also proved to display the ecosystem\nwith low complexity when it is presented in a two-dimensional manner, such as printed on\npaper.