There are two mobile applications that are used in collecting Trekker Surveys in the field: Survey123 and CRIS Mobile Pro. As described in the overview section, CRIS Mobile Pro is a browser-based application that does not need to be downloaded. However, Survey123 is an application that needs to be downloaded and installed from the App Store for iOS devices, Google Play for Android devices, or from the following URL for Windows or Mac computers: https://www.esri.com/en-us/arcgis/products/survey123/resources 

It is important to note that installing the Survey123 app on your device is a one-time operation. However, this is not to be confused with downloading the forms for a Trekker survey project, which must be done on each device for every Trekker survey project.