Import cavity monitoring dxf file
This function imports data from Cavity Monitoring System (CMS) and creates a triangulated model which is closed at both ends. This model can then be used by several other solids modelling functions.
Cavity Monitoring System, which is manufactured by OPTECH of Canada, permits comprehensive surveys of underground excavations to be performed. The CMS operates by taking measurements using a laser distance measuring unit mounted in a rotating probe to the walls of the stope or drive. These measurements can be taken at intervals as small as 1 degree as the probe rotates about each of 2 orthogonal axes.
To run this function: Choose File > Import > Cavity monitoring DXF file, or...
If the import is completed successfully, this function automatically sets the neighbours for the trisolation and validates the trisolation and sets its direction to SOLID. If you require a VOID you can change the direction using SET OBJECT DIRECTION.
The LASRD program supplied with the CMS provides a variety of output options to permit independent processing of the results of the survey. This function requires the data to be output to a DXF file with the MESH output option. The output data in this format has been specially prepared for triangulation and it permits rapid triangulation of even the 1 degree survey.
Define the CMS DXF MESH file to process
Location, ID number
Enter the location and ID number of the DXF file which has been created by the LASRD program using the DXF MESH output option. Note that this is the only type of DXF file which this function will import. Various comments in the file header are checked to ensure that the correct file type is being used.
Processing
Various stages of processing are performed on the data. Each of these are described here to aid in your understanding of the triangulation process.
- The MESH output option contains one DXF POLYLINE for each successive pair of surveyed rings.
That is, the first polyline contains the first and second rings, the second polyline contains the second and third rings, etc.
This implies of course that there is considerable duplication of points in the resultant string file as all but the first and last ring are duplicated.
This is tolerated however as there may be different numbers of points in the duplicate rings.
Different numbers of points occurs when, for some reason, the CMS has been unable to survey all the points in a ring.
By creating the data in this manner, the process of triangulating the rings is simplified considerably.
The first stage of processing is to import the polylines from the DXF file and then split each polyline into 2 distinct segments representing each of the rings contained in the polyline. This splitting process is performed to simplify the subsequent triangulation process.
- The next stage of processing is to create triangles between each of the successive pairs of rings which have by this stage been converted into discrete string segments.
- The first ring may be either a segment of some non-zero length or it may be a single point. This is dependant upon how the survey is conducted. If the first ring is a single point, then the triangulation to the second point will radiate out from this single point (there are in fact numerous points at the same X,Y,Z position). If the first ring is non-zero in length, then a point is created at the mean X,Y,Z position of all points in this segment and then the TRIANGULATE TO A POINT function is applied to fill the end in with triangles.
- The last ring will always be open as the CMS cannot transit through the full 180 degrees about the secondary axis of the instrument. A new point is created at the mean X,Y,Z position of all points in this segment and then the TRIANGULATE TO A POINT function is applied to the last ring to fill the end in with triangles.
Result
The result of this function is a completely triangulated, closed 3D model representing the stope or excavation surveyed using the CMS. The object created is identified as Object 1, Trisolation 1. If the import is completed successfully, this function automatically sets the neighbours for the trisolation and validates the trisolation and sets its direction to SOLID. If you require a VOID you can change the direction using SET OBJECT DIRECTION.
Further Processing
The 3DM created by this function may be processed by many other functions. Some tasks and the functions required to perform them are:
Calculate the volume of the object
| Task | Procedure |
|---|---|
| Calculate the volume of the object | Use the OBJECT REPORT function to ascertain the volume defined by the object. |
| Create horizontal or vertical slices of the object | Use SLICE OBJECT to define an appropriate axis and extract slices at intervals of interest |
| Determine the amount of ore remaining in a resource model defined in a block model | Use the BM VOL TON REPORT function to produce a resource report using the 3DM as a constraint to exclude material which has already been mined. |
| Visual inspection of the surveyed stope | Recall the 3DM into the graphics and enable hidden surface removal and then use the VIEWER to inspect the survey of the stope. |
Errors
Line nnn is not a valid DXF code
This error message indicates that a serious error exists in the DXF file and it cannot be processed. Create the DXF file again using the LASRD program and try processing it again.
Line xxx must be a CMS COMMENT 'NTC 3D SCAN FILE'
Line xxx must be a CMS COMMENT 'BY LASRD'
Each of these error messages indicates that the DXF file being processed has not been created by the LASRD program supplied by OPTECH of Canada with the CMS unit. The lines are in fact DXF comments and are expected in the first 4 lines of the DXF file.
Premature end of DXF file
This error message indicates that a serious error exists in the DXF file and it cannot be processed. Create the DXF file again using the LASRD program and try processing it again.
This DXF file does not appear to be in the MESH format as created by the LASRD program
Only DXF files created using the MESH output option of the LASRD program can be processed using this function. These MESH format DXF files contain certain data which indicate that it is in a MESH format and this data cannot be found in the file being processed. Create the DXF file again using the LASRD program with the MESH output option and try processing it again.
Error triangulating inside the first segment of the CMS survey.
Object will not be closed
Error triangulating inside the last segment of the CMS survey.
Object will not be closed
These error messages indicate that it has not been possible to create triangles inside the first and/or last segments of the CMS survey. The nature of the data captured by the CMS sometimes is such that the TRIANGULATE INSIDE SEGMENT function cannot produce an acceptable result. Try reducing the frequency of points around the segments by creating a new DXF file using the LASRD program with points separated by a greater angular displacement.