Using Interpolate to Map

WMS provides a lot of ways to interpolate data from one module to another. Since geometric objects may not line up exactly, values often need to be interpolated from one object to another. Common interpolation methods involve interpolating DEM and TIN elevation to a grid or mesh. However, a lesser known function is interpolating data to the feature objects on a map coverage.

Elevation values for a TIN orDEM can be interpolated to feature objects. Doing this will add the elevation values to the feature objects, specifically to points and vertices. To interpolate to feature objects:

  1. Select the map coverage with the feature objects that will receive the elevation values to make the coverage active.
  2. In the Project Explorer, right-click on the TIN or DEM containing the elevation values and select Interpolate | To Feature Objects.
Interpolate to Feature Objects command

The elevation values on the TIN or DEM will then be added to the features objects of the active map coverage. This process will only interpolate values to the active map coverage. Inactive map coverages will not be affected and only one map coverage can receive elevation values this way.

Interpolating to feature objects uses linear interpolation. If a point or vertex lies between a DEM or TIN elevation point, the interpolation method will estimate the closest approximate value. Elevation values will not be interpolated to feature objects that are outside of the DEM or TIN area.

Typically, interpolated to feature objects is done when you have manually added features objects without designating elevation during the digitization process. It can also be used in cases where the elevation values appear inaccurate and need to be changed to match a new set of elevation values. It may also be useful after importing map data that is missing elevation data.

Try out interpolating to feature objects in WMS today!

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Tips for Using the Hydrologic Modeling Wizard

WMS makes creating hydrologic models easier by providing the Hydrologic Modeling Wizard. This tool steps you through the process of developing a hydrologic model. Each step completes one of the elements needed for a complete hydrologic model. To make using this tool easier and more productive, here are a couple tips for using the Hydrologic Modeling Wizard in WMS.

Example of the Hydrologic Modeling Wizard

The first tip is that the Hydrologic Modeling Wizard is modular in nature. This means the wizard does not need to be closed in order to continue working in the WMS interface, unlike many other windows and dialogues in WMS. The wizard can be put to the side of your screen to let you work with other tools in WMS. Often this is necessary to adjust arcs in the Graphics Window or to import additional data. Once you are done with what you need to do, you can return to the Hydrologic Modeling Wizard.

It should also be noted that the Hydrologic Modeling Wizard keeps track of changes as you work in it. So if you should happen to close it, you can reopen it and get back to where you left off. However, you should make certain to save your WMS project before closing WMS in order to save changes made in the wizard to your WMS project.

Another tip is that you do not need to complete all of the steps in order. Some steps can be completed out of order. For example you may want to set the model you are using before completing earlier steps. Or, more often, you may have completed earlier steps outside of the wizard, letting you skip to later steps. That said, there are some steps that will not work unless a previous step has been completed.

Also note that you can always go back to earlier steps. Note that when doing this some steps that follow may have to be completed again.

The Hydrologic Modeling Wizard is a powerful tool to help you create hydrologic models faster. The tips presented here can also be applied to the other modeling wizards in WMS. Try out the Hydrologic Modeling Wizard in WMS today!

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Editing DEM Elevations

Do you have a Digital Elevation Model (DEM) that has elevations that need to be adjusted? Editing DEM elevations can sometimes prove difficult. However, with WMS you can edit the elevations of DEM files using several tools WMS provides for editing DEM elevations.

Here are a couple ways DEM elevations can be edited in WMS:

Editing Single Points

Some DEMs have a single point where the elevation is off. You can edit a single point in a DEM by using the Select DEM Points tool and selecting the point. You can then edit the point elevation by double-clicking on the point to bring up the DEM Point Attributes dialog where the elevation value can be changed.

Using Feature Arcs to Edit Elevation

Sometimes, the elevation of a DEM needs to be adjusted to follow a specific line, such as a river bed or proposed irrigation channel. The elevation in this location can be adjusted using a feature arc. This is done by selecting the feature arc then right-clicking and selecting the Edit DEM Elevations command.

Editing DEM Elevation using an Arc

In the Edit DEM Elevations dialog, you can change the elevation of the DEM along the arc. This can be done by selecting and changing elevation points on the arc in the profile window. For editing all of the elevation values along the arc, the dialog provides the following options:

  • You can offset all of the arc elevations by using the Offset elevations by a constant button.
  • You can set all of the elevation values to a constant by using the Set to constant elevation button.
  • Finally, you can use the Interpolate button to interpolate the values to between the first and last values on the arc. This will smooth out the elevation to create an artificial slope.

Using these tools makes adjusting the elevations of DEMs easier. Try them out in WMS today!

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Using Pre-Generated Polygons to Delineate a Basin

Delineating an accurate basin is an important part of a watershed project. WMS provides a number of tools for delineating a watershed basin. The Hydrologic Modeling Wizard is often used to step through the entire process of delineating a basin.

However, it is possible to delineate a basin using data from outside of the Hydrologic Modeling Wizard. In particular, the Drainage module contains tools for delineating a basin using existing project data.

For example, if you have a shapefile with polygons that gives the general outline of the basin, that shapefile can be used to delineate the basin. To use the shapefile polygons to delineate the basin, do the following:

  1. Import the shapefile into WMS. Verify the location is correct.
  2. If you have not already done so, add a DEM for the area of interest to the project.
  3. Generate the flow direction and accumulation, either by running TOPAZ/TauDEM or by importing it.
  4. Map the shapefile polygon(s) into feature polygons in a drainage type coverage.
  5. Place your outlet point(s) and digitize the streams. You can either manually draw the arcs, or load the streams from a shapefile. Be sure to verify that the arcs are set to Stream (not Generic) and that the directions are flowing from upstream to downstream (see "Stream Arrows" in the Drainage Display Options).
  6. Select DEM | Polygon Basin IDs -> DEM in the Drainage module.
  7. Select DEM | Compute Basin Data in the Drainage module.
Basin delineated from shapefile

Once you have a delineated basin, you can use the basin with the watershed modeling model of your choice. Be certain to review the basin to make certain it contains all of the area you need for your project.

WMS provides a large amount of flexibility in delineating a watershed basin in order to adapt to the needs of your project. Try out the different basin delineation tools in WMS today!

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