Frequently Asked Questions (FAQs) about GNOME
Here are answers to questions people have asked about a number of GNOME topics, grouped into the following categories:
- General questions about operating GNOME.
- Questions about Location Files, which are generally used in GNOME's Standard Mode.
- Questions about operating GNOME's Diagnostic Mode (the most advanced mode of GNOME), including how to make your own Location File or Diagnostic Save File.
General GNOME Questions
Q. What do GNOME movies look like?
A. View some oil spill trajectory movies created using GNOME.
Q. Why can't I include a GNOME-produced movie in my Windows PowerPoint presentation?
A. A GNOME QuickTime Movie (.mov) file may not play in PowerPoint on a computer running Windows, even if you have QuickTime installed. You may need to convert the file to an .avi (Audio Video Interleave) file. One of our users reported that he had successfully used the converter tool, "mov2avi", from Digital Digest. He used the command line "mov2avi.exe" with no compression, e.g., "mov2avi gnome_output.mov -c19", where the -c19 means choose option 19 for CODEC, which is "none".
Q. Why don't my GNOME dialog boxes display properly (in Windows)? In particular, the wind dialog box has the bull's eye partially hidden.
A. You need to set the screen display to 640 * 480 pixels or higher. There are two ways to do this:
- In the Start Menu, point to Settings, then to Control Panels. Select Display to get the Display Properties dialog, then select the Settings Tab and change your settings.
- Place your cursor on an empty portion of the screen, and then depress the right mouse button to view a popup menu. From the menu, select Properties to view the Display Properties dialog. Select the Settings Tab, and change your settings.
Q. How do I know which spill listed in the left section of the map window corresponds to which particular spill on the map?
A. A feature added to GNOME 1.2.6 offers some help with this problem. Beginning with this version, when you create a spill, you can name the spill in the dialog box. Then, in the left section of the Spill Information window, the spill name will document the details of your spill (pollutant type, quantity released, release time and position, and mass balance). We are still working on a feature that will help you match each spill name in the left section with its corresponding spill on the map.
Methodology and Verification
Q. Can you provide some documentation on the GNOME methodology?
A. Technical documentation for GNOME has been updated and is available on the GNOME References page.
Q. Has the GNOME model been verified?
A. The GNOME model is used in all NOAA Emergency Response Division (ERD) spill responses that require modeling. The model's algorithms function perfectly, but the user is the key to setting up the model in Diagnostic Mode for spill response. Because the primary forces that move the oil (wind, currents, etc.) are not generated by GNOME, but input by the user, the user is ultimately responsible for the results.
During spill response at NOAA ERD, the trajectory analyst selects the physics she believes are most appropriate for the spill and sets up the model accordingly. She selects the appropriate hydrodynamic model for the currents, simulating tides and hydrology as necessary, obtains a wind forecast from the NOAA National Weather Service, and estimates other parameters from reviewed literature and experience. Once the model is set up, a prediction is made and later compared with overflight information from on scene. If the current and wind predictions are accurate, and if the windage and diffusion parameters are set accurately in GNOME, then GNOME will generate very good trajectories. A 48-hour prediction of where the oil will go can be expected to be within 1-2 miles. If the model and observations differ, hindcast model runs are made to tune the model to the local conditions before the next forecast is made. The forecast winds and currents are usually not accurate enough to generate trajectories within 1 mile of accuracy after 48 hours. This is why GNOME supports user-specified uncertainty bounds, which are set according to the uncertainty in the input data. This is also why the GNOME input data is constantly updated during an event, and the model is rerun at least once a day during a spill.
Making predictions in tidally dominated areas is much easier than in eddy-rich offshore environments. The availability of local real-time data and good wind forecasts (from the NOAA National Weather Service) are key to good spill trajectory estimates.
GNOME's Location Files are tuned to simulate local climatological conditions to the best of our knowledge. Though tides are predictable, other environmental conditions are not so simple. Location Files are not appropriate for spill response, just as an almanac is not appropriate to predict the weather for a particular day.
Q. How does GNOME relate to TAP (Trajectory Analysis Planner)?
A. GNOME is our trajectory model and TAP is our Trajectory Analysis Planner. What's the difference? GNOME runs single trajectories. If GNOME is run thousands of times (using historical winds, tides, and currents), you can use TAP to analyze all those trajectories and calculate statistics from them.
TAP provides the probability of oil movement by looking at those thousands of trajectories. These probabilities allow planners to look at "what if" situations based on the regional oceanography and climate. Decision-makers can use TAP to decide whether to buy more boom or another skimmer, or where to site a lightering area.
TAP cannot be used in the event of a real spill. The situation on a particular day may not be well represented in the statistics, because spills often happen due to unusual circumstances. In the case of a real spill, GNOME can be quickly set up to represent the environmental conditions of the spill. TAP is best used for planning, when it is not known what conditions will be when a spill occurs.
Q. How do I get GNOME Analyst?
A. GNOME Analyst is a NOAA ERD application that converts the number and position data for "best estimate" splots into oil density contours and converts the location data for "minimum regret" splots into an uncertainty bounding contour. GNOME Analyst is used in-house and isn't currently available for download. We are, however, working on software to replace GNOME Analyst, and it will be publicly available when it's complete.
Q. What's the difference between GNOME and OSSM (On-Scene Spill Model)?
A. You might call OSSM (b. June 3, 1979) the father of GNOME. OSSM was the first trajectory model developed at NOAA ERD, and was written as a command line Fortran code application. GNOME was developed next and was first released March 16, 1999. GNOME is written in C++, which was chosen for two reasons: (1) the addition of a graphical user interface to aid ERD responders and outside users in quickly setting up models, and (2) the support of objects in C++, enabling nifty abilities in Diagnostic Mode.
Q. Why do the evaporation estimates for GNOME and ADIOS differ, and which one should I use?
A. GNOME uses a simplistic 3-phase evaporation algorithm, which is appropriate for simple drills and educative comparisons. The oil weathering model, ADIOS (Automated Data Inquiry for Oil Spills), has the better evaporation and oil fate estimates compared to GNOME. ADIOS also has an extensive oil library.
Software Specifications and Legalities
Q. Do we need to obtain either individual or site licenses to use GNOME?
A. No. GNOME may be freely used and distributed at no charge.
Q. Does the Windows version run in all Windows 2000 versions?
A. Yes, the latest version of GNOME does (as do all versions from 1.1.4 on).
Q. Is the Windows version a 32-bit or 64-bit application?
A. GNOME is 32-bit (though it will still run on Windows 7).
Q. When was GNOME first released?
A. GNOME 1.0 was released on March 16, 1999.
Bugs and Glitches
A. We've corrected a number of bugs in earlier versions of GNOME. Please send reports of any problems or bugs you encounter to the GNOME Wizard.
Here is a list of significant bugs in earlier versions of GNOME:
- Earlier Windows versions of GNOME were missing the windage button in the overflight dialog. Fixed 02/18/07.
- Earlier Windows versions of GNOME had a bug affecting users who were importing NetCDF currents or winds. The base time cannot be earlier than January 1, 1970 00:00 GMT, otherwise the Windows function localtime() returns an error and GNOME defaults the base time to January 1, 1970 00:00 GMT. GNOME still loads the file but the times are all off. We added an alert for future versions of GNOME. Fixed 01/06.
- Earlier versions of GNOME allowed users to output MOSS files for GIS systems with the Minimum Regret (Uncertainty) solution turned off; however, the GIS tool requires that Uncertainty be turned on for the run. We added error checking with a message to alert users to turn on the Uncertainty solution and re-run the scenario before outputting GIS files. Fixed 12/05.
- Earlier versions of the Santa Barbara Channel Location File for Windows had a bug in Diagnostic Mode. Opening the map dialog would cause an error due to conflicting messages from the Wizard command file. (Mac file did not have this problem). Fixed 08/05.
- Earlier versions of GNOME had a problem with multiple entry dialog boxes in Location Files. These versions would highlight the last entry box, which was confusing to the user. The new version highlights the first entry box. Fixed 06/04 with GNOME 1.2.5.
- Earlier installers didn't work properly for Windows XP. Fixed 05/03 with GNOME 1.2.3.
- GNOME Diagnostic Mode users could not open recent .sav files from previous versions of GNOME. Fixed 10/02 with GNOME 1.2.2.
- The Mac version of the Santa Barbara Channel Location File had a bug that made the currents go a little faster than they should. Fixed 10/02.
- Earlier versions of GNOME set the age of spilled pollutant incorrectly. Fixed 11/00.
- Earlier versions of GNOME allowed oil to "jump" over land, and did not properly initialize oil age for oil weathering. Fixed 6/00.
- Versions of GNOME earlier than v. 1.1.1 did not show the wind fields when you went through the Location File a second time.
- GNOME versions 1.1 and later were corrected to read Location File Save (.lfs) files made in GNOME 1.0 for an evaporation-related bug.
- Windows versions of GNOME earlier than v. 1.1 incorrectly displayed years after 1999 in the map window list.
- The GIS output from versions of GNOME earlier than v. 1.1 had a sign error in the output longitudes, causing the data to be read in and placed in the opposite hemisphere.
- Earlier versions of the Prince William Sound Location File for Windows were missing some background flow information (Mac file did not have this problem). Fixed 10/5/99.
- In earlier versions of the Central Long Island Sound Location File, the tidal reference file was not correct. Fixed 6/8/99.
- In earlier versions of the Columbia River Estuary Location File, river scaling was not scaling river transport. Fixed 6/1/99.
- In earlier versions of the Prince William Sound Location File, uncertainty horizontal mixing was too high. Fixed 6/2/99.
- Versions of the Prince William Sound Location File previous to 4/2/99 were missing the detailed help topics for using GNOME.
Q. (Mac only) Some of the dialog boxes are too big to fit on my display. I can't seem to cancel out of them easily. What should I do?
A. The Mac version is set for a screen resolution of greater than 640 * 480 on a 15-inch monitor. If your resolution and screen size don't allow you to see the entire dialog box, you can move it so that you can see the bottom. Ordinarily when you grab a dialog box with the cursor, you can't move it far enough up to make the top bar move out of view. Here's the trick: If you very carefully grab it with the cursor on the very outer side edge, you can them move it up as high on your monitor's real estate as you would like. You may also wish to change your monitor's resolution to something higher.
Q. I can't create movies. What's the problem?
A. Most likely, you just need to install QuickTime, a free download from Apple Inc. Both Windows and Mac users need QuickTime to view movies. It's also possible that you don't have enough hard drive space for the moving-making process and writing out the movie file. When there's too little space, GNOME appears to go through the process of making a movie, but no file appears.
Location File Questions
Q. For what regions will you be creating Location Files?
A. You can see our list of upcoming Location Files on our GNOME News page (see the section, Upcoming Location Files). Each Location File will be made available as soon as it's completed. If you don't see a Location File for a region you'd like to model, please see the next question.
Q. Can you make a Location File for my region?
A. We're currently preparing Location Files to support the work of the U.S. Coast Guard's Marine Safety Offices (under the Oil Pollution Act of 1990, we're mandated to support the Coast Guard). We do provide trajectory support for drills, including preparing GNOME Location Files, on a "time-available" basis. Requestors go into a queue, with the U.S. Coast Guard at the top of the list, other U.S. federal and state agencies next, and industry/private companies next. If the Coast Guard is participating in your drill, they can work with their local NOAA Scientific Support Coordinator to decide whether or not to submit a request for a Location File. From time to time, in support of some of our international projects, we also will create Location Files for regions outside of the U.S.
Another option is for you to learn to use GNOME in Diagnostic Mode to create your own Diagnostic Save Files. You then can use these files to model potential spills in your area. However, be forewarned that creating Location Files and Diagnostic Save Files requires regional physical oceanographic expertise.
Diagnostic Mode Questions
Q. How do I open GNOME's Diagnostic Mode?
A. To change to Diagnostic Mode, from the File menu, choose Preferences. In the Preferences window, click the Mode tab then, under Model Mode, choose Diagnostic. (If you want to work predominantly in Diagnostic Mode, you can instruct GNOME to open in that mode each time it starts up. On the right side of the Preferences window, under Startup Model Mode, choose Diagnostic.) When you change to Diagnostic Mode, GNOME will alert you that you are changing to a mode that requires detailed knowledge of trajectory modeling and will suggest that you first save your Location File settings.
Q. What do I need to make my own Location File or Diagnostic Save File?
A. Most people make their own Diagnostic Save Files. Unless you plan to market a Location File, you can put all the same physics in a Save File without having to construct the Wizard expert system or the dialog boxes. We've created a page, Setting Up GNOME for Your Region, to guide you through this process.
Q. Can I use my own currents or winds in Diagnostic Mode?
A. Yes, you can import maps, currents, estimates of eddy mixing, and winds into GNOME. Currents can be imported from any model that uses a rectangular, curvilinear, or triangular grid. GNOME can use wind information from a time series at a point, or a wind model on a rectangular or curvilinear grid. You may want to check out GOODS, an online tool that helps GNOME users access publicly available ocean currents, winds, and base maps from various models and data sources. You can then download the files in a format that can be read directly into GNOME (e.g., current and wind files in netCDF; map files in BNA format). See also the Web page, Setting Up GNOME for Your Region, as well as some of the question/answer pairs below.
Q. Where can I get currents and winds for my area?
A. You can obtain currents and winds from several sources, depending on your region of interest. We've created the online tool, GOODS, that helps you access publicly available ocean currents and winds from various models and data sources. You can then download the files as netCDF files that can be read directly into GNOME.
Another source you may want to check is Ocean Watch: Central Pacific, one of numerous sources of current/wind data. On the Ocean Watch site, choose the option, "Live Access Server (LAS) for Satellite Imagery and Data."
To download currents, choose one of the Sea Surface Height and Geostrophic Currents datasets (06. Monthly; 14. Weekly; or 15. Near Real-Time Weekly). Check the box for "Sea-Surface Height + Geostrophic Currents," then click Next. In the Select View box, choose your desired view. In the Select Output box, choose NetCDF file. In the Select Region box, choose your region of interest. Click Next. A file called "LASoutput.nc" will download.
To download winds, choose one of the QuikSCAT Ocean Surface Winds datasets (07. Monthly; 16. Weekly; or 20. 3-Day). Check the box for "Wind Speed + Wind Speed Vectors," then click Next. In the Select View box, choose your desired view. In the Select Output box, choose NetCDF file. In the Select Region box, choose your region of interest. Click Next. A file called "LASoutput.nc" will download.
Q. Where can I get digital shoreline data easily?
A. The USGS Coastline Extractor is a source of detailed coastline data for the U.S. and the world. You can use these data files in GNOME, but you will need to modify them to follow BNA format. We've created an online tool called GOODS to help you translate the digital shoreline data to BNA format.
The Coastline Extractor page also makes river locations and political boundaries available; however, you should check that any political boundaries in your area of interest are up-to-date.
Q. Will I ever be allowed to "paint" in my current vectors?
A. No. Algorithms that "spread" velocities between observations by simple smoothing operations do not conserve mass or water, in our experience. We require hydrodynamic model output for currents so that the current fields reflect the physics the user intends: mass conservation, Coriolis effects, geostrophic balance, Ekman dynamics, etc.
Q. What are the arrows on the map?
A. Arrows indicate (1) velocity vectors if "Show velocities" is selected on one of the current patterns or (2) movement distance in one timestep if "Show Currents" is selected under Model Settings.
Q. Why do the movement arrows look strange?
A. Try turning off or scaling down the Random diffusion. Depending on the currents, the diffusion can add a little randomness to the pattern or completely dominate it. The Windage setting in the Variable Winds window may also cause this. Normal values of windage are 1-4 percent.
Q. Why are the arrows so far apart?
A. We'd bet you are looking at the Movement grid with the zoom set far out. Try zooming in on an area of interest, and the arrows should look better (closer together in absolute distance). The spacing of the arrows for the movement grid is calculated on the map window size; the size of the arrows is calculated on map scale. Zooming in will increase the size of the arrows and their apparent spacing.
Q. What are the triangles where the water should be?
A. "Show Grid" must be selected for one or more of the current patterns. This shows the finite element grid used for creating the current pattern.
Q. Why is my spill just a single dot that I can hardly see?
A. You probably have the diffusion turned off. Try a very low value of diffusion (e.g. 50 cm2/sec) so that you can see the spill, without allowing the diffusion to dominate the model outcome.
Q. Does the GNOME ArcView Extension work with the new ArcGIS Desktop versions (i.e., 8.x, 9.x) or does it only work with ArcView 3.x?
A. The GNOME ArcView extension is for 3.x. You can use the GNOME trajectory import tool, created in May 2005, to import GNOME "splots" or NOAA trajectory products into ArcMap 9.x/10.x. Both tools are available in the GNOME Toolkit.
More Information about GNOME
GNOME References: Find references for some of GNOME's methods and uses.
Even more questions, comments, or suggestions? Contact us.