(The Modelling module is required for this procedure.)
This procedure is used to form a three dimensional digital terrain model. Refer also to the Terrain Modelling topic in the Concepts section of the help.
You may obtain additional help by clicking the underlined topics. If you do select an underlined topic, you may return to this procedure by clicking the Back key.
- Ensure that the required data base is open.
Refer to the procedures for creating or opening a data base. - It is recommended that you use object colour display rather than colour number display as this
will more easily allow you to identify the contourable points and lines to be used in the modelling
process.
Refer to the procedure for selecting the mode of colour display. - Since model formation is group and block sensitive, check that you have the required groups displayed and that the required block is active. Only points and lines defined by an active block and on the displayed groups will be used in the model. If there is no block active, points and lines on all displayed groups are used. Refer also to Group concepts and the Block command
- Select the Terrain Modelling task. Then select the Modelling/Validation command and use the Terrain Modelling Validation dialog box to validate the data set for any errors that could result in an incorrect model.
- Any errors or warnings encountered in the validation process are written to the ERROR file. View or print any such errors using the Terrain Modelling/Errors! menu.
- If there were errors encountered in the validation process, use the Computations task to locate
and rectify the errors.
Use the Examine/Find/Errors command to quickly locate the objects on the screen that are associated with the errors. - When the validation errors are corrected, repeat step 4 until the validation process is successfully carried out with no errors reported.
- Select the Modelling/Form Model command and use the
Terrain Model Formation dialog box to form the digital terrain model.
Use the Region Size field to set the required region size.
Use the Search distance field to set the required search distance. - Any errors encountered in the modelling process are written to the ERROR file. View or print any such errors using the Terrain Modelling/Errors menu.
- If there were errors encountered in the modelling process, use the Computations task to locate
and rectify the errors.
Use the Examine/Find/Errors command to quickly locate the objects associated with the errors on the screen. - When the modelling errors are corrected, repeat steps 4 to 8 until the validation and modelling process is successfully carried out with no errors reported.
- On successful model formation, use the Display Features command to display the contours for visual inspection and quick identification of any gross point elevation errors.
- To correct any point elevations, select the Computations task and use the Edit/Elevations command. Upon changing an elevation, use the Redraw tool to reflect the changes to the contours.