GMS

Converting Units

By aquaveo on August 22, 2018

Seeing which units are being used in a project or for a particular object within the project is fairly easy. Converting the units from, for example, U.S. feet to meters, can introduce problems into a project if you do not do it in the correct way.

Reproject

Reprojecting the data involves moving the data from one coordinate system to another. So if your data is in a UTM coordinate system in meters and the rest of your project is in a State Plane projection that uses U.S. survey feet, reprojecting can change the data to match. Conceptually, the data will remain in the same location, but the data will be adjusted to the new units.

To reproject a dataset:

Right-click on the dataset in the Project Explorer and select Reproject.
In the Reproject dialog, the current projection is shown on the left. On the right side, set the new projection and units.

When converting units through reprojection, keep in mind that Z values (elevations) don’t always convert correctly. Round off errors sometimes occur when reprojecting data. In general, reproject does well in changing the X and Y units. The Z value, if it has been set as the bathymetry, typically also converts units well using the reproject option. Other datasets often do not convert between units using the reproject method.

When converting from rasters to scatter sets, the elevation is usually recognized and converted correctly.

Dataset Calculator

Datasets units can be converted using the Dataset Calculator. This is often necessary when the data has been reprojected, but not all of the datasets can be converted using that method. For example, a velocity dataset or conductivity data.

To convert a dataset with the Dataset Calculator:

Select the desired dataset in the Project Explorer.
Select the Data Calculator macro, or the Data Calculator command or the Dataset Toolbox command in the Data menu.
Select the dataset to convert, then multiple or divide the dataset by the conversion value.

There are a few numbers it is useful to have when doing these conversions:

0.304800609601 meters is equal to one U.S. Survey foot
3.28083333333 U.S. Survey feet are equal to one meter
0.3048 meters is equal to one International foot
3.28083989501 International feet are equal to one meter

Note that there are many datasets that will not work with the Data Calculator.

In the end, make certain all the data being used in your model is in the correct units. Having mismatched units will typically create model errors and generate inaccurate results.

Try reprojecting data or using the Data Calculator to convert units in GMS, SMS, or WMS today!

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Using Mass Flux Computations

By aquaveo on August 8, 2018

Are you wanting to compute the mass flux for a group of MODFLOW boundary conditions? The mass flux is the rate of mass flow per unit area, or mass per time per area. Computing this can quantify the strength of contaminants at a particular location in your model.

Use the MT3DMS or MT3D-USGS model to compute the mass flux at specific location. To do this:

First create and run a MODFLOW model.
Then create an MT3DMS or MT3D-USGS simulation with all relevant parameters set and contaminant species defined.
Make certain the Transportation Observation Package is turned on in the MT3DMS/RT3D Packages dialog.
If it is not already in the model, create a conceptual model with the MT3DMS/MT3D-USGS defined species.
Create a map coverage with the observation point option for the species turned on.
Create points on the coverage at the locations where you want to to observe mass flux.
Assign these points as observation points and enter attributes as needed.
Access the Transport Observation Package dialog through the MT3DMS or MT3D-USGS menu.
Turn on the Compute mass flux at source/sinks option.
Run the model.

MT3MDS/MT3D-USGS will compute the mass flux at each observation point. The computation is done using the units set for the input concentration. Typically, these are the units used for the display projection in GMS. So if your project is using U.S. survey feet, then your mass flux will be calculated as ft^3*mg/L. If varying units are used in the concentrations, then conversions must be done before calculating the mass flux.

The mass flux will be contained in a dataset file with the “.mfx” file extension. This file can be opened using any text editor. The file will show the calculated mass flux for each time step and for each source or sink included in the model.

Hopefully, you now understand a little more about calculating mass flux in GMS. Try out mass flux calculations and other features in GMS today!

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5 Ways to Select Arcs in GMS

By aquaveo on July 18, 2018

Everyone knows you can select an arc in GMS by using the Select Arcs tool and clicking on the desired arc. But did you know there are five different ways to select one or more arcs? Here’s a quick rundown of all of them:

Use the Select Arcs tool to click on a single arc. This is the most common way to select an arc, but it only allows you to select one at a time. If you have multiple arcs you need selected, there are better, more efficient ways to select them.
Use the Select Arcs tool while pressing the Shift or Ctrl key to select multiple specific arcs. This allows you to select only the desired arcs for whatever purpose you wish. This method includes all of the precision of the first method, but can take a long time if you have many different arcs to select. The next three methods allow you to more quickly select larger numbers of arcs.
Use the Select Arcs tool to drag a box around multiple arcs to select them. All arcs where both nodes of the arc are contained within the box wil be selected. Arcs where one node is outside of the box will not be selected. The click and drag method provides a quick method for selecting multiple arcs, but is not as accurate.
Use the Select All command in the Edit menu to select all the arcs in the project. Just make sure to have the Select Arcs tool selected first so GMS knows what to select. The Unselect All command can be used to deselect everything when you’re done, if desired.
The Select With Poly command in the Edit menu lets you draw out a polygon around the arcs you want selected. Keep in mind that both ends of an arc must be within the polygon in order for it to be selected.

Try out these options today in the GMS Community Edition.

Edit: This post was updated on 7/20/2018 to correct information in methods 2 and 3.

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Using Software Graphics Mode

By aquaveo on July 11, 2018

Have you ever noticed in your Start Menu that GMS, SMS, and WMS all have a version of the software executable that says "Software Graphics Mode"? Do you wonder what this is used for?

The software graphics mode was created to help resolve issues when there is a mismatch between the XMS software and the graphics card on a computer running the software. While we work to have XMS function on a wide range of graphics cards, some graphics cards do not support current versions of XMS.

When there is a mismatch, you might experience difficulty running the software. Issues we’ve seen happen include:

Having objects disappear from the Graphics Window when drawing new objects.
When changing views, objects in the Graphics Window disappear completely when they should still be visible.
Objects that appear in the Graphics Window that cannot be hidden or removed.
In some cases, the XMS application will not start.
In other cases, the XMS application will close suddenly.

Using the software graphics mode causes the machine running the XMS application to bypass the graphics card. Think of it as “safe mode” for XMS. Doing this places a heavier burden on the machine’s memory and processor, but it typically allows the XMS application to be used without the problems being caused by the graphics card.

To access the software graphics mode, go to your Start Menu and select the desired XMS executable with "Software Graphics Mode" in the title.

If using the software graphics mode resolves the issue you were experiencing, there is still one more thing to do: update your graphics card drivers.

Updating your graphics card drivers often resolve the issues being caused by the mismatch between the XMS application and the graphics card. Follow the standard procedure for updating the graphics card drivers for your operating system. In some cases, you will need to go to the graphic card manufacturer's website to update the drivers.

Once the graphic card drivers have been updated, you can usually continue to use the XMS application without using the software graphics mode.

And if updating the graphics card drivers doesn’t work, do not hesitate to contact Aquaveo Support for additional help.

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