Digitiser setup
Installing a digitiser with the software involves a number of steps. Firstly you must physically connect the digitiser to your computer. This step is described in the Installation chapter of this manual. Next you must perform the following steps to configure the digitiser to the software.
- define the communications parameters
- define the digitiser message format
- define the digitiser scaling parameters
To install or reconfigure a digitiser choose Create Digitiser tablet from the main menu. This will display the CONFIGURATION menu.
To run this function: Choose Create > Digitiser tablet > Configuration, or...
Note that this is a modal setup, meaning that each of the steps must be performed in order.
Fields on the Select Digitiser form
Digitiser
Enter the name of the digitiser you wish to create or the name of an existing digitiser to reconfigure.
Choose Apply to display the DIGITISER SETUP menu. This menu allows you to define the various digitiser parameters. The menu items should be selected in top to bottom order for the definition of a new digitiser as this is the logical sequence of events. For an existing digitiser the order of selection is not significant.
Once a digitiser is defined a file is created in the SSI_ETC: directory which contains all the parameters pertinent to the digitiser.
If the digitiser specified already exists the message
Digitiser SSI_ETC:name already exists
will be displayed.
If the digitiser specified does not currently exist then the message
New Digitiser SSI_ETC:namewill be displayed.
Digitiser Communications
This function allows you to define the communication parameters on the port to which the digitiser will be connected to the computer. These parameters consist of the port identifier, baud rate, parity, number of data bits, number of stop bits and whether a beep is to be issued for each point digitised. Note that the parameters entered here only control the communications parameters for the computer. The digitiser must be configured so that it matches the communication parameters defined for the computer.
To run this function: Choose Create > Digitiser tablet > Communications port, or...
Port
Enter the identifier for the port to which the digitiser is connected. The full path name must be included. Enter the identifier for the port to which the digitiser is connected. The full path name must be included. Computer ports are named differently according to the hardware platform you are working on. Some examples are "WINTAB" for Windows "com1:" for DOS, "/dev/ttya" for SunOS, "/dev/tty00" for HPUX, etc.
| Note that if WINTAB is chosen then the digitiser hardware must be compatible and configured to accept the WINTAB driver communication. It is also important to note that the message format is not required to be defined if using the WINTAB driver. |
Baud
Enter the baud rate at which the computer and the digitiser are to communicate. Typical values are 4800, 9600, 19200.
Parity
Enter the parity setting that the computer and digitiser are to communicate. Valid settings are none, odd or even. Usually parity is set to none.
# Data bits
Enter the number of data bits which are to be used. Valid entries are 7 or 8.
Note:On DOS based systems the combination of no parity and 7 data bits does not work.
# Stop bits
Enter the number of stop bits which are to be used. Valid entries are 1 or 2. Usually only one stop bit is used.
Beep
If you want a beep to be sounded for each point which is digitised then enter "Y" otherwise enter "N". This feature can be enabled or disabled very easily when you are digitising from a map.
Once the communications parameters have been defined the software will accept input from the digitiser. If you generate one or more points on the digitiser the string of information sent by the digitiser to the computer will be displayed in the message window. This will be useful to determine the digitiser message format which is the next step in configuring the digitiser.
Digitiser Format
This function allows you to define the format of the character string which is generated by the digitiser. It is absolutely essential that you define this correctly otherwise the coordinate values interpreted will be incorrect.
To run this function: Choose Create > Digitiser tablet > Message format, or...
A form is displayed to allow you to define the message format. Note that once the communications parameters have been defined correctly the software will display the raw digitiser message string in the message window whenever a point is generated. This will be helpful in determining the message format.
Number format
This defines the type of format for the digitiser x and y coordinates. A default value of UNKNOWN is displayed for new digitisers. Valid entries are:
- REAL - the digitiser send real numbers
- HEX - the digitiser sends hexadecimal numbers
- UNKNOWN - the format is unknown and x and y values will not be translated.
Generally the number format used by the digitiser will be REAL.
Message length
You must enter the number of characters in the digitiser message string.
X offset
Enter the offset from the start of the message string to the character position at which the x value commences. For example if the X value starts at the first character then the offset is 0.
X length
Enter the length (the number of characters) which represent the X value.
Y offset
Enter the offset from the start of the message string to the character position at which the x value commences. For example if the Y value starts at the tenth character then the offset is 9.
Y length
Enter the length (the number of characters) which represent the Y value.
When the form has been applied, the software can display the decoded X and Y coordinates in a formatted manner in the message window. Digitise a few points to see if you have defined the format correctly and if the results are incorrect then change the format until it is correct.
Digitiser Scale
This function allows you to define parameters which will assist in determining the scale of any map which you may digitise from. When digitising from a map the approximate plan scale can be displayed to verify if the transformation parameters have been defined correctly.
To run this function: Choose Create > Digitiser tablet > Set tablet scale, or...
To define the digitiser scale you must select two points on the digitiser tablet which are as far apart as possible (to achieve the best results) and determine the real world distance between these two points. The units which you enter the points in will be determined by the setup feature "distance units" in the defaults.ssi file. A value of "m" or "ft" will be displayed for the units to be entered depending on this setting.
| Prompt | Action |
|---|---|
| Digitise the first point | Digitise the first position on the tablet |
| Digitise the second point | Digitise the second position on the tablet |
A form is displayed to allow you to enter the distance and to advise you of the units which are required for this distance.
| Distance between points | Enter the distance between the two points in the units requested. |
Note:This has no effect on the transformation of coordinates from the tablet coordinate system. The value displayed is the number of digitiser units per metre (or feet if imperial measure is used). This value is used to determine the scale of the plan which is being digitised when using the digitising function.
Digitiser End
This function completes the definition of the digitiser setup. A form is displayed to allow you to confirm or cancel the creation of the named digitiser definition file.
To run this function: Choose Create > Digitiser tablet > End Configuration, or...
To confirm the creation of the digitiser setup file with the new parameters press the Apply button. To cancel the creation of the digitiser setup file with the new parameters press the Cancel button.
If you have trouble establishing successful communications with the digitiser you must check two things.
- Confirm that the communications parameters defined using Digitiser Setup match exactly the communications set on the digitiser. You may need to consult your digitiser manual to determine how to change these settings.
- Confirm that you have a cable between the computer and the digitiser which will permit communications to proceed. Typically this will be a cable which conforms to the RS232C specification. If you don't know how your digitiser cable should be configured consult a hardware technician.
Digitiser Tablet Menu
After successfully completing the preceding steps, the digitiser will be ready for use. Prior to using the digitiser in the Graphics module you must place the Digitiser tablet menu on the digitiser tablet.