12da to from GIS: Difference between revisions
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= Introduction =
The .12da file must be saved in ANSI encoding, not UTF.
When importing or exporting between 12D and GIS, specify the file to be translated:
* If the file has a .mif extension the program converts it to a .12da file.
This process is useful for importing 3D breaklines, for example a road design, directly into TUFLOW.
Several useful options are described in the table below. Particularly noteworthy are the following options:
* -zln: useful when river bathymetry in the DTM is poor because aerial survey data are inaccurate where water or dense vegetation is present.<br>
This option allows a section to be carved through the DTM along the river based on a cross section survey.
▲* If the file has a .mif extension, the program converts it to a .12da file.
▲* Note, when converting from a .12da file to a .mif file without any options, 12da_to_from_mif automatically creates a .mif/.mid file suitable for use by Read GIS Z Line. This is useful for importing 3D breaklines (eg. of a road design) directly into TUFLOW.
▲** Of particular note is the -xs option to generate a TUFLOW 1D cross-section database from a 12D DTM.
▲** This approach is far more preferable to extracting cross-sections manually and is much better than extracting cross-sections from a grid based DTM (eg. Vertical Mapper or Spatial Analyst) as it only extracts points where the DTM triangle sides intersect the cross-section line, thereby keeping the number of points in the cross-section profile to a minimum, and also improving the accuracy of the profile.
=Options (switches)=
'''TABLE 1: 12da_to_from_GIS Options (Switches)'''
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! width=85% | Description
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!colspan="2" style="background-color:#005581; font-weight:bold; color:white;"| When converting from a
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|"-zln"|| When converting a .mif file to .12da file, if zln is specified polylines are interpreted in the same manner as a TUFLOW 3D breakline (see Read GIS Z Line) such that any points snapped to the polyline are used to set the elevations of any vertices along the polyline that do not have points snapped to them. The first attribute in the .mif file must be the Elevation. (Note, when converting in reverse from a .12da file to a .mif file without any options, 12da_to_from_mif automatically creates a .mif/.mid file suitable for use by Read GIS Z Line.)<br>
This is useful for creating 3D polylines for 12D where an elevation does not exist at a vertice. It is particularly useful where a river’s bathymetry in a DTM is being created from cross-section surveys, and the DTM operator wishes to use the elevations at the cross-section survey points, but needs to put more shape into the breaklines being digitised between the cross-sections so as to carve out the river’s bathymetry into the DTM. Using 12da_to_from_mid with the zln option will interpolate elevations at every string vertice, something that 12D does not offer (as far as we know!).
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!colspan="2" style="background-color:#005581; font-weight:bold; color:white;"| When converting from a .12da file to a
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|"-hip"|| When converting a .12da file to a .mif file will include any 12D hipdata polylines.
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