HEC-MetVue allows users to override the time zone of the input data with the "Override Default Timezone (GMT)" option within its data readers. The primary use for this option is to provide a Time Zone when the file/DSS record does not explicitly define a time zone. A secondary purpose is when the user believes that the Time Zone contained within the file is incorrect.
Task 2 will demonstrate how to override the default time zone setting when reading in source data.
Copy a New Map Window.
Right-Click on the "Extent Constraints" Map Window and select "Map Window" → "Copy Map Window..."
Name the new Map Window "Override Time Zone" and select Ok.
Note the Default Time Zone.
At the top of the "Override Time Zone" map window, note that the existing (default) duration of the selected data is from "29Aug2021 0000 - 01Sep2021 0000 GMT."
Override the Default Time Zone.
Next, we will override the default GMT timezone to view the data within one of the local timezones within the LMRFC extents–Central Standard Time.
Open the DSS Data Reader by expanding the "Override Time Zone" Map Window Node in the HEC-MetVue Explorer Window.
Right-Click on the TIN node and click on "Select DSS paths…"
The LMRFC precipitation grids are already selected since we created a copy of the "Extent Constraints" map window.
Expand the "Active Read Constraints/Overrides" options and select "Override Default Timezone (GMT) Used to Read Source Data."
Select the "Greenwich Mean Time" button to launch the "Select Data" dialog.
Within the "Select Data" dialog, set the Group to "America."
This narrows down the available Time Zone options for easier lookup.
Set the Time Zone to "Central Standard Time (observes DST)" and select "OK."
Select "OK" within the data reader to display the data within the Map Window within the Central Standard Time (CST) timezone.
Hover over the "Central Standard Time" button to view the Tool Tip associated with the "Override Default Timezone (GMT)" function.
Tool Tip
This button shows the timezone that will be used to read all new paths selected. All paths shown in the 'selected paths' list displays the timezone that was in effect when the path was selected. Changing the timezone setting only impacts the timezone for newly selected paths.
The tool tip tells us that time zone changes only impact newly selected paths so we must remove and re-select the data again.
Select "Remove All" to remove all selected pathnames.
Ensure that the "LMRFC" B-Part and "QPE" F-Part are still selected.
Select "Add All" to re-select the data.
Note that since "Show in Display Time Zone" is selected in the Available and Selected TINs tables that the pathname timestamps are now shown in Central Standard time and now run from 29 August 2021 05:00 to 01 September 2021 04:00.
Select "OK" to add the data once more to the Map Window.
View Data in CST.
At the top of the "Override Time Zone" map window, note that the updated timestamp of the same dataset "29Aug2021 0500 - 01Sep2021 0500 GMT."
The timestamp is still referenced within the GMT time zone, but it has been shifted +5 hours to represent the CST time zone.
The timezone override is also noted on the TIN node within the explorer window:
Remember, overriding the default time zone can be useful if the dataset does not already have a time zone associated with it or if the user believes the data is referencing an incorrect time zone.
Task 3 will demonstrate additional overrides that are available within the HEC-MetVue DSS Data reader.
