The Joint Training Data Services (JTDS) is a web-based set of services that provide Modeling and Simulation (M&S) ready data and scenario development tools to the DoD Enterprise to support Joint and Service theater level constructive & virtual training. JTDS provides persistent web access to an Order of Battle Service and a Terrain Generation Service (TGS) that leverage unique data repositories and tools to generate training scenario initialization files. Historically, the terrain generation service proved difficult to maintain and extend given its closed architecture, stove pipe terrain generation capabilities and stagnant source data collection. Given the lessons learned from the legacy terrain generation service, a technology update and refresh was undertaken to create an updated terrain generation service that supports open source formats, accessibility through an easy to use web interface, and dynamic terrain during runtime. The new terrain generation service heavily utilizes open simulation data standards and geospatial web mapping interfaces to share and distribute simulation products and geospatial data. The open source Common Database (CDB) structure is used as the underlying source data format based on its ability to promote sharing, reuse and utility by storing geospatial and simulation data sets in non-proprietary formats structured to facilitate rapid access, rendering and visualization. Open Geospatial Consortium (OGC) web standards are used to maximize connectivity to the CDB by enabling most geospatial tools to natively visualize and navigate the Terrain Repository. This paper will share the lessons learned and architectural updates of the new terrain generation service.