Task 6 – Combine TINs Temporally & Spatially ("Both").

The "Both" combine TINs method allows for applying spatial combination when data is coincident in time and applying temporal combination when the points are coincident in space. Combining TINs "Both" Temporally and Spatially can be useful when you'd like to determine event totals based on a combination of overlapping datasets.

Task 6 will compare precipitation grids from the Lower Mississippi River Forecast Center (LMRFC) and South East River Forecast Center (SERFC) first by individually combining each source temporally for an entire event.
Next, the LMRFC and SERFC precipitation grids will be combined both Temporally and Spatially which considers the values of both datasets in the areas that they overlap.

Create a New Map Window.

Create a new map window to view the SERFC temporal event totals.

Right-Click on the "Pearl-Part A" Session and select "Sessions and Maps" → "Add Map Window..."

Name the new Map Window "SERFC Precip" and select Ok.

View SERFC Precipitation Temporal Event Totals. 

Let's look first at the SERFC precipitation totals for the 29-31 August 2021 event.

Right-Click on the "SERFC Precip" TIN node and click on "Select DSS paths..."

Select the following DSS file:

...\HEC-MetVue_DssDataReader\HEC-MetVue_DssDataReader_Start\Data\DSS\precip.2021.08.dss

Select "Temporally" from the "Combine TINS" menu at the top of the Select Data dialog box. 

For now, we are interested in the temporally combined precipitation totals of each precipitation source. Later we will compare the individual (SERFC vs. LMRFC) source totals with the combined source totals.

Filter the B-Part to "Pearl River" and the F-Part to include data from "SERFC-QPE." 

Within the "Available TINs" dialog, highlight the SERFC-QPE records for the Pearl River from 29 August 2021 00:00 to 31 August 2021 24:00.

Select "Add Sel" to select the highlighted TINs. 

Select "OK" to combine the selected SERFC TINs temporally and add them to the map window.

The SERFC precipitation data is combined temporally and the basin average totals for the event are displayed.

If necessary, zoom in to the TIN extents by right-clicking within the Map Window → Encompass Data → TIN.

Note that the SERFC precipitation data does not fully cover the Pearl River watershed. The western portions of the Middle Pearl-Strong, Middle Pearl-Silver and Bogue Chitto subbasins are not covered as indicated by the dashed red line that was drawn in below:

Question: What is the basin-average precipitation total for the Lower Pearl subbasin for the 29-31 August 2021 event (from the SERFC precipitation grids)?

Review LMRFC Precipitation Temporal Event Totals. 

The 29-31 August 2021 event totals for the LMRFC-QPE data were determined earlier within Task 2. Review the LMRFC event totals by re-opening the "LMRFC Precip" map.

Right-Click on the "LMRFC Precip" map window heading within the Explorer Window and select "Open Map Window." 

The LMRFC precipitation data is combined temporally and the basin average totals for the event (from Task 2) are displayed once again.

Question: What is the basin-average precipitation total for the Lower Pearl subbasin for the 29-31 August 2021 event (from the LMRFC precipitation grids)?

Now that we've examined the basin-average (temporally combined) totals for both the SERFC and LMRFC datasets, we will apply the "Both" Temporal and Spatial TIN combination method and compare the combined results to the individual datasets.

Close Extra Map Windows.

We will first close the extra map windows that will not be used within the comparison.

Close All Map Windows except "SERFC Precip" and "LMRFC Precip."

To close the Map Windows, right-click on each Map Window listing within the Explorer Window and select "Close Map."

Notice how closing the extra Map Windows greys out their listing within the explorer window, leaving just the Map Windows of interest active.

Copy a New Map Window.

Create a new map window for the Temporal and Spatial ("Both") combination of the SERFC and LMRFC datasets for the 29-31 August 2021 event. We will save time by copying the "LMRFC Precip" map window which already contains the 29-31 August 2021 grids from the LMRFC.

Right-Click on the "LMRFC Precip" map window and select "Map Window" → "Copy Map Window..."

Name the new Map Window "LMRFC-SERFC Precip" and select Ok.

A copy of the "LMRFC Precip" Map Window will appear with the new name "LMRFC-SERFC Precip."

Combine TINs Temporally & Spatially ("Both").

Right-Click on the "LMRFC-SERFC Precip" TIN node and click on "Select DSS paths…"

Notice that the LMRFC-QPE grids are already selected since the new Map Window was created as a copy of the "LMRFC Precip" Map Window.

Select "Both" from the "Combine TINS" menu at the top of the Select Data dialog box. 

Filter the B-Part to "Pearl River" and the F-Part to "SERFC-QPE."

Select "Add All" to select all of the precipitation grids from the SERFC from 29 August 2021 00:00 to 31 August 2021 24:00.

All QPE grids from both the SERFC and LMRFC should now be selected and appear in the "Selected TINs" dialog box.

Select "OK" to combine the selected SERFC and LMRFC TINs and add them to the map window.

The SERFC and LMRFC precipitation data is combined both temporally (over time) and spatially (in areas of overlap). The basin average totals from this process for the selected event are displayed in the map window.

 Notice the Compute Progress bar at the bottom of the screen as the data loads:

Note that the basin-average precipitation total for the Lower Pearl subbasin is different than both the SERFC and LMRFC values. This is because both the LMRFC and SERFC grids are being considered throughout the areas that they overlap (such as the Lower Pearl subbasin). 

Question: What is the basin-average precipitation total for the Lower Pearl subbasin for the 29-31 August 2021 event (from the SERFC & LMRFC spatially combined totals)?

Compare the Datasets.

Next, let's compare the event totals from the SERFC, LMRFC and Combined datasets. 

Select the "Tile Windows" () icon to view all active Map Windows within the "Pearl-Part A" HEC-MetVue session.

Notice that all three active map windows are now displayed within the "Pearl-Part A" HEC-MetVue session. 

Sync Map Window View Extents.

If necessary, Zoom in closer to the Pearl River watershed in all of the Map Windows.

Syncing the Map Window view extents is a quick way to display the same extents within all Map Windows.

Right-click on a Map Window that's already zoomed in to the desired extents and select "Sync Session Maps to This Map Window."

All map windows will be resized to the same zoom level as the selected map window.

Question: What differences do you notice between the two datasets and the different TIN combination methods?

Prior Task(s):

Task 1 - Open the HEC-MetVue Program

Task 2 - Combine TINs Temporally - Single Dataset

Task 3 - Compare Different Datasets

Task 4 - Combine TINs Temporally - Multiple Datasets

Task 5 - Combine TINs Spatially

Current Task:

Task 6 - Combine TINs Temporally & Spatially ("Both")

Next Task(s):