The "read only" GpsBlog APIs are documented in Swagger YAML format. Swagger UI functionality allows the documentation to be easily read and the APIs exercised interactively. Try it out here.
Try the Postman button to exercise the GPS Blog APIs in Postman - the Postman "collections" having been imported from the Swagger YAML. There is also a Postman "environment" file available for import here that provides a set of initial parameter values that will produce results when calling all the APIs.