Hydrology output
In the following text, each output screen of the visualization tool is discussed. The visualization tool splits the screen into various screens to display the output of the model. The number of windows created depends on the type of output displayed. The tool always reserves an ASCII terminal (non graphics) for interacting with the user. The first screen (Figure 1) provides various options including a watershed summary (no graphics) and spatially distributed soil loss, nutrients, runoff and feedlot movement (graphics) output of a watershed.
Options 2-5 (Figure 1) move to the next screen (Figure 2) where the appropriate output option maps are displayed. This screen is divided into numerous windows depending on the output option chosen. The screen is divided in half, having a series of top row windows and bottom row windows with an ASCII terminal. The top row windows display the output maps (Table 2). A scale for each of the output maps is displayed showing the color and the numerical value associated with it. The color of the output maps range from green-yellow-red, with increasing intensity of output. The right hand top corner window displays the watershed map with cell numbers by laying a grid on top of it for reference. Below this cell number map, the aspect map of the watershed with arrows pointing in the flow directions is displayed. In the bottom row, two windows display the output and input statistics for any cell. The left window shows cell inputs. The output window shows a bar chart and key features of the output option statistics for the same cell. The default cell statistics displayed in the bottom row windows are the statistics for the outlet cell of the watershed. The tool provides error checking and also explains what to do at each step.
In the next section, options 6-9 of Figure 1 are discussed.
Analyze Different Scenarios: This option allows the user to visualize and analyze a different simulation for the same resolution of the original run. The user is asked to enter the name of the ASCII AGNPS file name without its extension. The AGNPS run that was started with the visualization tool is called the 'current' and the simulation that was selected using this option is referred as 'selected' hereafter in this documentation. The program checks the resolutions between the 'current' and the 'selected' runs and checks for the same file names. Then the program creates the 17 output maps (Table 2) and displays the 'current' and the 'selected' output maps on the screen in the top row windows. The default output is the sediment movement maps. Bottom row windows display the output histograms of the 'current' and the 'selected' simulations. The left bottom row window corresponds to the 'current' input/output window and the right bottom row window corresponds to the 'selected' input/output.
Under this option the user has the same options (Figure 2) discussed earlier in this document. In addition to this, the user can alter the output visualization/analyzation to other model outputs such as sediment, nutrients, feedlot or runoff movement. While using options 2 and 3 (Figure 2), the user is asked to select either input or output to view in the bottom row windows.
For options 5 and 8 (Figure 2), the user is asked to select either the 'current' or the 'selected' simulation results to view in a window. This option is one of the strongest features of the visualization tool for analyzing different scenarios simultaneously.
Save Output Maps: This option allows the user to save the maps created using the visualization tool. The user can save all or only those outputs of interest, which include sediment, N, P, COD, and runoff. The program asks the user to enter a map name for saving the output maps. The program attaches proper extensions depending on the type of outputs (Appendix 1). Please refer to the appendix 1 for the extensions of different map names. It also contains reserved map names that should not exist in the current mapset. Do not remove the filename_cell_num map, since all output maps created in the visualization tool are reclassed from the created cell number map.
Exit to GRASS (to come back type 'return'): This option allows the user to exit to the GRASS temporarily to perform normal operations under the GRASS GIS tool. To come back to the same menu in the visualization tool, type return and hit enter.
Quit: This option takes the user back the GRASS prompt and exits from the visualization tool. The output maps created will be removed from the current mapset, but will not affect those maps that are saved using the Save Output Maps option. If you plan to use output maps at some future time, be sure to save them.
1. Zoom: Allows users to zoom in or zoom out of any section of the watershed by choosing one of the displayed windows. Once the zoom operation is performed, the tool automatically adjusts or redisplays all the maps in the top row windows to the same area, enabling users to take a closer look at an area of interest. This option is particularly helpful on large watersheds. Once the Zoom option is selected, the tool requests for a window to perform zoom operations. The user has to use the left mouse key to click on one of the top row windows and then click on the right mouse key to complete the selection process. Then the zoom function asks the user to use the left mouse to click on a place to define the area in the selected window, and then drag the mouse to the desired location and click on the right mouse key to complete the zoom process. Always follow the instructions displayed on the ASCII terminal. Failing to do so can cause the program to stop. Similarly, the unzoom operation can be performed.
2. View a cell: This option allows the user to enter a cell number of interest to display the statistics of that cell's inputs and outputs in the bottom row of windows. The displayed bar chart depends on the type of option chosen in the initial screen (Figure 1). The cell number can be either entered directly using the keyboard in the ASCII terminal or the mouse can be used to point out a cell on the graphics monitor using the left mouse key after choosing one of the top row windows. The window selection process is detailed in the Zoom section. This feature is helpful to visualize characteristics of both inputs and outputs of a critical area.
3. View an area output: This option allows the user to select an area from one of the top row windows and displays the average input and output statistics for that area in the bottom row windows. Here also, the user is asked to select a window from the top row windows using the selection procedure explained earlier. Then using the left mouse key, the user selects a corner of the desired area and drags the mouse to build a box. Click the right mouse key to complete the process. This information is helpful to study the statistics of the critical areas and its neighbors. Using this option, one could estimate average inputs and outputs for a field which should assist in making further decisions.
4. Toggle between flow direction map and viewing window location: This feature is helpful when users use Zoom to view any particular section of the watershed. After a couple of zoom operations, users may loose track of which part of the watershed is displayed. This option toggles between the flow direction map and the whole watershed map showing a box around the current viewing area.
5. Show the watershed summary output: The summary at the outlet of the watershed for all the outputs is displayed in the ASCII (non graphics) terminal. This option is useful to correlate cell outputs with those of watershed outputs to make decisions.
6. Display ranges of output maps: This option allows users to visualize output maps (Table 2) for a specified range between maximum and minimum values of the output (Figure 1) chosen. This helps users locate critical areas easily. For example, users can use this option to display problematic areas that are exceeding the soil tolerance limit (T factor). Options are available to save the displayed maps for later reference, compare various scenarios or overlay one map on another in order to make decisions.
7. Display user's choice map: Users have an option to display a cell map, overlay a map on another map or display a vector map. The chosen map can be displayed on one of the existing windows or users have an option to create a new window anywhere in the graphics monitor to display the map. Further, the map chosen for display can be one of the AGNPS output maps (Table 2) generated from the AGNPS output files or one of the existing maps in the database. From of the users/decision makers point of view, this option is helpful to reach conclusions about management strategies. For example, by overlaying a field boundary or property boundary on an erosion map, fields within critical limits can be located. Combinations of various outputs can be viewed simultaneously on the designed graphic windows. On selection of this option, the user is prompted for the map to be displayed. If the user selects to display the map in one of the existing windows, then the selection of the window operation is performed followed by the selection of the type of display. This could be to display a cell map, overlay a map on another map or display a vector map. Maps are listed for selection. If the user selected the option to create a new window to display a map, then the program requests a location to start the window. Using the left mouse key, drag the mouse to create a box of desired size and click the right mouse key to end the process.
8. Draw Cumulative and Frequency Distribution Statistics: This option allows the user to view the percentage of cumulative and frequency distribution area curves for any of the output maps (Table 2) or selective input variables for either user specified ranges of intervals/classes or for 10 equal ranges of intervals/classes between the maximum and minimum of the selected variable. This option is helpful to see how that particular variable is distributed both cumulatively and the number of occurrences in that interval. It is believed this information in combination with spatial referenced maps could be of very useful in the decision making process. The steepness of the curve shows how that variable is increasing within a corresponding range. By choosing this option, the program requests a window to display the statistical curves. Then, the program asks the user to select either an input or output variable for which to draw the curves. The user then has the option of keeping the previously selected X-axis intervals/classes or can select a new range of intervals/classes. The selection of new ranges of intervals can be done in one of two ways. Either the user can select 10 equal intervals between the maximum and minimum of the selected variable or he can enter the ranges between the maximum and minimum values. In either case, the number of intervals can't exceed 10.
9. Restore the initial screen: This option restores the original or initial display screen that was initiated when one of the options from Figure 1 was chosen.
10. Exit to GRASS (to come back type 'return'): This option allows the user to exit to the GRASS temporarily to perform normal operations under the GRASS GIS tool. To come back to the same menu in the visualization tool, type return and hit enter.
11. Quit: This option takes the user back to the initial screen (Figure 1). If the user has created any maps using option 6, the program asks if these are to be saved before quitting.
Appendix 1: List of AGNPS output maps and reserved map names
Hydrology output
X: Refers to the name supplied by the user. The maps are saved with the extension in the current mapset.