METHODOLOGYHModule MAPGRID uses the System Plot Package modules in the NCAR graphicsLpackage to generate mapgrids. The NCAR system produces a device independentImetacode file. This metacode file may be read by a translator program toJcreate device specific files for many types of output devices. A partial Klist of translators are: Tectronix, DEC Laserpriters and Calcomp plotters.-For a complete list refer to the NCAR manual.MPlot is a dummy main routine which shall call the application routine XGDATA Iwhich in turn shall call MAPUSER. In this instance MAPUSER controls the Nplotting module XPLOT. A program mode flag is passed from XGDATA to MAPUSER, Kwhich in turn shall pass the mode to XPLOT. MAPUSER controls the sequence of calls to XPLOT.JThe design of MAPLOT mimics the design of XGUSER in that it is a five callGmodule. Each mode has a specific function, below is a list of the modedefinitions for XPLOT..LT;/ Mode 1) Initialize the plot characteristics..ELJIn Mode 1, scaling parameters for variables and the label lengths for the Iaxes shall be passed to XPLOT. XPLOT in this stage shall invoke modules MMAPINI, and MAGINI. Mapini shall retrieve user input through a separate TAE Dinterface, these input parameters are variables associated with the Ginititialization of the MAP projection routines (e.g. Projection name, Ncentral meridians, standard parrallels, line types for the projection, etc). LMAGINI the second of the initialization modules is responsible for all user Minput for the generation of the mapgrid. The parameters retrieved in MAGINI,Nare Latitude and Longitude limits, Grid line intervals, labeling intervals forHthe Latitude and Longitude axes. All parameters retrieved are placed in/commons for use by all other plotting routines..LT+Mode 2) Initialize a Sequence, start frame..ELPMode 2 shall perform the initialization of a new frame (map grid with labels). NIf multiple plots are being produced, then mode 2 shall close any already openMframes and draw a new grid for the next sequence of data to be plotted. The Nplotting of a Mapgrid in a specific projection shall follow as outlined below:JMapgrid shall control the invokation of XGRID. Mapgrid shall determine ifKthe plotting interval needs to be broken up into two steps. This may occurJif the ranges to be plotted span 0.0 longitude, (e.g. 240.0 to 240.0, the Lfirst interval shall be from 240 to 0, the second from 0.0 to 240.0). XGRIDLplots the grid lines for any of the 7 projections. XGRID determines whetherKthe line type is straight, circular, or neither. From these classificationsHXGRID plots the latitude or longitude lines dependent on their line typeIclassifications. XGRID shall initialize parameters to be used in module JMAPLAB. MAPLAB shall use the x and y label coordinates to plot a label in Kthe appropiate place for the selected projection. The line type (dashed orHconnected) and a flag indicating which axis is to be plotted, (latitude Jor longitude), shall be passed to Maplab. Utilities LCHECK, and CONV are Mutilities which aid in determining if the delta longitude, or delta latitude Nincrements have been satisfied by the specified label increments, if this has Nbeen satisfied, LCHECK is positive indicating that a label should be plotted, Motherwise no label is plotted. Control is then returned to XGRID, where the Nmodules specified above are continually called until the limits in the X and Ydirection are satisfied..LTMode 3) Plot a set of points..ELMMode 3 shall be the mode where the points are plotted. In this mode the userMmay have chosen the option to plot the points with a vertical offset in whichFcase the points are plotted and the magnitude of the point is plotted Operpendicular to the direction of the points. If the user selects point plots,.this shall also be performed during this mode..LT Mode 4) Stop curve, stop frame..ELOMode 4 shall be used to flush any remaining points in the plot package softwarePto the metacode file. This mode shall be invoked at the end of a frame of data,Ga frame may be defined as an individual sequence or a set of sequences..LT!Mode 5) End the plotting process..ELMMode 5 shall terminate any plotting parameters and return program control to the invocation module (XGDATA)..BR.PAGE