If the optional file name argument is given, isopot will attempt to perform a Load operation on this file. (The file must be an isopot parameter file.) If no file is specified, you will have to select one later, or set all required parameters from scratch.
At the bottom of the display, isopot prints the following menu prompt line:
This is the main menu, the top level in a hierarchy of menus. To initiate an operation in this menu, or in any of the other menus in the hierarchy, type the first letter of an item in the menu. Some items will perform an operation and/or prompt you for input; other items will simply bring you to another menu, one level lower in the hierarchy. An alternative method of selection is to highlight the item you want from the menu, then hit RETURN. The space bar will cause the next item to be highlighted; the BACKSPACE key (or DEL key, if this is your erase key) will highlight the previous item. If an item is highlighted, the last line of the display briefly describes the choice, or shows the next menu. Pressing the ESCAPE key at any time will usually bring you back to the main menu. Some operations bring you back directly to the main menu after completion. Others leave you in some lower level menu, in which case the position in the menu hierarchy is shown at the left of the menu.
The Mouse and Tablet selections bring you into the "drawing program" section of isopot. If you use the Mouse selection, you will be able to draw using the standard pointing device on your graphics terminal. This is usually the mouse, but it can also be a joystick or a tablet. If you select Tablet, then you will be using the "Houston Instrument HIPAD Digitizer" as the pointing device. In either case, you will be using the selected pointing device to move the cursor, draw the diagram, and make selections from the drawing program's menus (including the "Quit" selection). Once you quit the drawing program, you are returned to the isopot menus, and the pointing device is no longer used. See DRAWING PROGRAM below for more details.
In order to use the HIPAD digitising tablet as your pointing device, there are a few steps required to set it up. First, the HIPAD must be connected to the proper serial port on your system. (Currently P7 on the MC535, and P1B on the MC5400.) Note that the connector on the back of the tablet is not a standard RS232 connector. It requires a special cable, not just any RS232 cable, and this cable is not reversible. You must also ensure that the environment variable INITABLET is properly set, to indicate which special file is used to read the serial port, and which command is used to initialise it. Normally, it should be set to something like: "stty 4800 cs8 istrip -parenb icanon < /dev/hipad". The < must be present, since isopot looks for the device name after the last < in the string.
You can export the diagram by selecting Draw/File/Write. You will be prompted for the name of the diagram file to be created. If it exists, it will be overwritten. The diagram is stored in the file as ASCII text. It consists of one or more series of coordinate pairs, with each series terminated by a single "-1". A series represents a segment of connected points, and separate series are not interconnected, although they can intersect. The coordinates are integers representing 100ths of millimetres.
The Draw/File/Read selection allow you to import a diagram file of the same format. You will be prompted for the name of the diagram file to be read. If you currently have a diagram in memory, and you haven't written it out to a file yet, it will be lost.
Once all parameters have passed the test, the diagram is drawn, then the isopotential contours are calculated and drawn.
Since the number of measurement points in the matrix is normally relatively small, it would not be possible to generate a reasonable contour map without somehow interpolating levels between the given points. Isopot uses a "Bicubic interpolating spline" function, described in Spline Algorithms for Curves and Surfaces by H. Spath, to fit a continuous surface through the given points over the entire area of the matrix.
The program can then follow contours at various levels on this continuous surface. It first searches around the borders of the map area for level transitions, then follows the contours around, staying at the same level, until the contour line hits the border at another point. These are the open loops. Then, it scans inside the map area for level transitions, and follows those contours around until it reaches the starting point. These are the closed loops.
If you press the ESCAPE key while the contours are being drawn, isopot will finish drawing the current contour line, then cancel the Go operation. Any other key pressed during this operation is ignored (and thrown away). If the standard input is redirected to read from a file, instead of from the keyboard, this feature is disabled. This will allow you to follow the g command with other commands in this file. This feature also works with the Plot/File and the Plot/Plotter operations.
You will be prompted for a parameter file name. The current file, if one was loaded, is the default. The file name suffix .iso is appended to the given file name, if it has no suffix. The parameters are then saved in the named file, overwriting any previous contents.
First, if any of your current parameters have been modified, isopot asks you if you want to save them. If you answer N, it will load the new ones, discarding the current ones. If you answer Y, it will perform a Keep operation, i.e. it will ask you in which file you want to keep your current parameters.
Next, you are prompted for the name of the parameter file to load. Once the name is entered, the parameters will be loaded from the file, replacing your current set. If a file with the given name does not exist, and the name does not have the .iso suffix, then this suffix will be added to the name.
The measurement matrix consists of three or more tracks, each containing the same number (three or more) of measurements taken at a number of levels (or depths). The matrix can appear in the file in either "track-major" ordering or "level-major" ordering. For "level-major" ordering, the file begins with two integers: the number of levels, then the number of tracks. Following these is the matrix of real numbers: all measurements across the first level (in all tracks), then all measurements at the second level, and so on. For "track-major" ordering, the file begins with three integers: first, a "-1," then the number of tracks, and finally the number of levels. Following these is the matrix: all measurements down the first track (at all levels), then all measurements down the second track, and so on. The units in which these measurements are given is totally arbitrary. They can represent volts, millivolts, degrees, millimetres, or anything else, as long as all measurements in the matrix are given in the same units.
After the matrix, the file can contain the positions of the tracks and levels. The track positions are specified by the keyword tracks, followed by a real number for each track position. The levels (or depths) are specified by the keyword levels, followed by a real number for each level. The units in which these numbers are given are also arbitrary; they are only used to specify the relative spacing of tracks and levels. If these are omitted, even intervals between tracks and/or levels are assumed.
The isoprep program generates measurement matrices, in "track-major" order, from runs of captured data. Each run it uses corresponds to a single track. The depth information is taken from one of the captured channels. See isoprep(1) for details.
The Measurements/Add-matrix selection will also read in a matrix from an ASCII text file, and will add it to the current measurement matrix. You are first prompted for a weight, or scaling factor, by which the measurements in the matrix being read will be multiplied. You will then be prompted for the name of the measurement file to be read. The dimensions of the new matrix must match those of the current matrix, and the levels and track positions associated with the two matrices must also match.
The Measurements/Clear selection will clear out your current matrix. This will allow you to start a new weighted sum of matrices, using the Add-matrix operation, to give a weight to the first matrix of the sum. (The Read-matrix operation also clears out your current matrix, so you can use it to start a new sum, but it will always use a weight of 1, rather than asking you for a weight.)
The Measurements/Write-matrix selection will write out the current measurement matrix, and associated levels and track positions, to an ASCII text file. You will be prompted for the name of the measurement file to be created. The default file name is the name of the last measurement file written or read. The program will ask for confirmation before overwriting an existing file.
A Quit operation from any lower-level menu simply brings you up one level.
The View/Shading selection draws a pattern over the current display, shading alternate levels in the data. The pattern is "exclusive-or'ed" with the current graph, so a second View/Shading selection will erase the first. The shading density varies with the "# steps in map" parameter. Also, the levels shaded are determined by the "Level gap" parameter. The purpose of this is to verify the effect of some of your parameter settings. It indicates the position of the map on the diagram, and the precision selected by the "Level gap." If done after a Go operation, it will also help identify any contour lines which may have been missed, due to a too small setting for the "# steps in map" parameter.
Most of the screen is used as the drawing area. The box at the bottom of the screen is the drawing program's menu. There is always one item in the drawing program's menu which is underlined. This indicates the current mode of operation. Pressing the button while the cursor is in the drawing area has different effects, depending on which mode is currently selected. Initially, the Trace mode is selected, allowing you to trace out the diagram.
Once Trace is selected, you can move the cursor into the drawing area, to a place where you want to start tracing. Hold down the button, and move the pointing device along to draw a continuous segment of the diagram. When you release the button, the program stops tracing, to allow you to point to another place and begin tracing another segment.
When tracing a diagram with the HIPAD, the resulting diagram, when plotted on the pen plotter, will be the same size as the original, unless you used the ZoomIn option (see below), or reduced the plot by using the layout(1) program.
While in the Labels mode, with the Text type selected, you can point to any place in the drawing area, and click the button. This places a label handle (a small square box) on the display. You can also point to an existing label handle, hold down the button, and move the handle. If you move it off the bottom of the drawing area it will be removed.
The last handle placed has an X through it, indicating it is the current label handle. You can select another by pointing to it and clicking the button. Any text you type on the keyboard will appear over the current label handle. You can erase the text by hitting the BACKSPACE key (or DEL key, if this is your erase key) to erase one character at a time, or you can type a Control-U to erase the entire string.
Any label handle you place over the contour map area, which has no text above it, indicates a numeric label. In the final graph, the levels at the contours closest to these will be indicated. The label handles will not be shown in the final graph, whether the labels contain text or not; the handles are just used for positioning the labels.
Special processing is performed on any text label which contains a dollar-sign character ($). This character is used to indicate the beginning of one of the following substitutions. A sequence of the form "$$" in a label is replaced by a single dollar-sign character.
A sequence of the form "$<name>" in a label is replaced by the value of the parameter indicated by the given name. The parameter names are those indicated by a View/All operation. For example, "$<Level gap> mV intervals" will yield something like "0.025 mV intervals" on the final display.
A sequence of the form "${name}" in a label is replaced by the value of the environment variable indicated by the given name. For example, "User: ${LOGNAME}" will yield something like "User: fred" on the final display.
A label containing the sequence "$l" is replaced by a three line legend indicating the pen colour and line type used for negative, zero, and positive contours (i.e. those below, on, and above the threshold level selected by the Set/Disp-opt/Line-types/Thresh. operation). If a number follows the sequence "$l", it is taken as the length, in millimetres, of the sample lines in the legend (20 mm by default).
A label containing a sequence of the form "$snumber units" is replaced by a scale legend. Any text after the "$s" will appear as a label, and below this label, a centered horizontal line is drawn. The line's length is determined by the number given, divided by the distance between the smallest and largest levels (depths) in the measurement matrix, and multiplied by the distance between the Origin and Depth indicated below. For example, if the Origin and Depth are 88 mm apart on the diagram, and this corresponds to an actual depth of 4 mm, as indicated in the level information of the measurement matrix, then the label "$s1 mm" will yield the label "1 mm", with a 22 mm line below it, on the final display, indicating a magnification factor of 22. The number must be given in the same units as the level information of the measurement matrix for this to work correctly.
While the Markers input type is selected, you can point to any place in the drawing area, and click the button. This places a marker, or tag, on the display at that location. You can also point to an existing marker, hold down the button, and move the marker. If you move it off the bottom of the drawing area it will be removed.
The last marker placed has a square box around it, indicating it is the current marker. You can select another marker by pointing to it and clicking the button. You can change the size and appearance of the current marker, and all subsequent markers, by hitting single keys on the keyboard. The size can be selected by hitting any digit key, to select half-millimetre increments. The initial size is 6, meaning 3 mm wide, and can go up to 9, or 4.5 mm. A size of 0 will give just a single point. The type of marker shown can be selected with one the following keys:
. A solid (filled) circle. o A circle outline (not filled). b A solid square block. s A square outline. t A triangle outline. d A diamond outline (square rotated 45 degrees). x An X-shaped cross.
The initial type is o, the circle outline.
When setting any one of these three points, the bottom of the display will show the distance from the origin of the Depth and the Width, as well as the angles of the lines from the origin to these points.
All of these parameters are set in "text mode", where you are prompted for a value for the parameter, and you type in the number or string desired.
The Line-types selection brings you to a menu where you can change the line types used to draw the contour lines. Here, the View selection shows you the line types available. You can use any of these line types to draw contours of levels Above, Below, or On the threshold level. The Thresh. selection lets you change this threshold level, which is usually 0. Due to the relatively limited screen resolution, dotted and dashed lines will not wrap around curves as nicely on the screen as on the plotter, and may appear solid at some places.
The Pens selection brings you to a menu where you can change the plotter pens used to draw the contour lines. You can use any pen number, from 0 to 8, to draw contours of levels Above, Below, or On the threshold level. The threshold is the same as for Line-types above. If you set any of these three pen numbers to 0, as they are set initially, then the corresponding levels will be drawn using the "Data pen," as selected by the Plot/Data option.
The Overlay selection brings you to a menu where you can choose to overlay two types of markers on your diagram. You can enable or disable the marking of Tracks, which are shown as lines at the track positions given in your measurement matrix file, from the first level to the last. You can also enable or disable the marking of Points, which are shown as circles at all intersections of track positions and levels given in your measurement matrix file.
The 3-D selection brings you to a menu where you can set various parameters for a three-dimensional display of the contour map. The program will generate a 2-D projection of the 3-D figure, from the specified perspective. You can specify how high contours will climb on the Z-axis, by setting the Level-disp. parameter. It indicates the distance, in 100ths of millimetres, from one contour level to the next. For proper perspective, you must give the distance of the diagram from the screen and from the viewer, also in 100ths of millimetres. A Screen-distance of 0 (the default) is acceptable, and means that the centre of the diagram is at the centre of the screen. Initially, the Viewing-distance is 0, which disables 3-D plotting. To enable 3-D plotting, set this parameter, usually to something like 100000, or 1 metre. The Inclination, Tilt and Rotation parameters will rotate the viewer's perspective around the X, Y and Z axes of the diagram, respectively. These angles are specified in degrees. The Eye-shift/Horizontal and Eye-shift/Vertical parameters allow shifts in the viewer's perspective. One might generate two representations of the same figure: one with a horizontal shift of -3500 (or 35 mm to the left), and the other with a horizontal shift of 3500, representing the views seen by the left and right eyes. (The distance between your eyes is about 70 mm.) By viewing the two plots stereoscopically, a 3-D image will be seen.
Increasing this parameter will increase the precision of the contour lines, but will also increase (quadratically) the amount of time it takes to draw the map. Decreasing it will speed things up, but it may cause some contour lines to be missed, or make some contour lines a little jagged. The default value should be large enough for most data, unless the level gap is quite small in relation to the range of measurements in the matrix. A larger number of steps may be needed if the density of contour lines is quite high.
Certain other errors are caught by the program, triggering an "INTERNAL ERROR" message. If this happens, the current set of parameters will automatically be saved in a special directory, for later examination. You will be able to continue in the program, but bear in mind that any results produced at the time of the error will almost certainly be incorrect.
If you detect a bug which does not cause one of the above actions, but produces results which appear incorrect, save your current parameters so that the error can be reproduced, and make a note of the problem.
In all of these cases, keep the relevant data and parameter files on-line, and report the bug or error.
When isopot reports an error, whether an internal error or a user error, it asks you to hit a key to continue. After reading the message, hit a key from the main keyboard, such as SPACE, RETURN, or ESCAPE. The program will then return to the current menu, and allow you to continue.
If you redirected the standard input to the program, so that it reads its commands from a file, rather than the terminal, then errors (user and internal) will be handled differently. Instead of printing the message, reading the next "keystroke" from the file, and continuing, these errors are fatal; the program will show the message, and then terminate. However, warning messages are not fatal, and the program will simply continue.
The command, "isopot -core corefile", will cause isopot to start up in the usual way, then search for the parameters in the given corefile, a core dump previously produced by isopot. This allows you to recover parameters after a fatal error, and is usually used only for debugging. It does not allow recovery of the diagram or labels.
The command, "isopot -dispmenus", will cause isopot to print a listing of its hierarchy of menus, to the standard output, then quit. In this mode, the graphics terminal is not required.
As for most other X Window programs in this package, the following X command line options are accepted: