The Reader+ Editor compute engine is built on MetCalculator, but designed for a specific set of computations common when processing and combining data from multiple data sources. Given that the utility is built on MetCalculator, it's backed by the same JSON file as MetCalculator operations, and therefore it's serialized to/from that JSON file. Additionally, reliance on MetCalculator means that the Reader+ Editor is not necessarily only applicable for Gridded Data. For example, in HEC-MetVue, it is possible to load irregularly spaced data, such as data gathered from a gage network.. Although TINs can be input, the Reader+ Editor always projects onto a user specified grid, and therefore all output data will be in a grid.

Within the Reader+ Editor, there are one or more Reader+ Dataset Preprocessing which can be merged into a consistent set of grids. Processing of the Data Products and merging procedure are provided on their own pages, but a flowchart showing an example Reader+ Editor compute is provided below. In this example, there are three Data Products following the example in Reader+ Editor images. HRRR is assumed to be the most reliable, and therefore is provided a priority of 1. NBM-QPF06 has a priority of 2 and NAEFS has a priority of 3. Additionally, HRRR has 1Hour grids, but NBM-QPF06 and NAEFS have 6Hour grids. Each Data Product starts by reading and projecting the data. Next, any gaps in the Data Product grids are filled within the Data Product time window (time between first and last available grid), and missing cell values are filled. After filling, temporal transformation is performed. Note that temporal transformation is only applied to NBM-QPF06 and NAEFS, as those are at a longer time step than the output time step. The last steps in the Data Product processing are the data screening and setting the parameter name. Once Data Product processing is completed, the grids are selected based on priority, which selects HRRR grids for January 21st 2024 at 00:00 through January 21st 2024 at 18:00, then NBM-QPF06 is selected for January 21st 2024 at 18:00 through January 28th 2024 at 24:00, and finally NAEFS is selected for January 28th 2024 at 24:00 through February 4th 2024 at 00:00. After this merging, there is a consistent set of grids, and if necessary, final missing data filling operations will be performed.