SMS:Cross Section Notes

The cross section tools have a number of features:

1. Cross section databases can be created from a text file.
2. Cross sections can be interpolated along the centerline.
3. Cross sections can be trimmed to annotation types.
4. A surface (TIN) can be created by matching annotated points on cross sections.
5. A centerline coverage can be created from annotated cross sections.
6. HEC-RAS cross section data can be used.

Some things to watch for when using the cross section tools:

• Always check for overlapping cross sections after interpolation is complete.
  • Trimming cross sections prior to interpolation can help prevent overlapping afterward.
• Before converting to a TIN, cross sections must be manually cleaned up.
• Converting a shapefile to a Centerline coverage can be a slow process.
  • Converting to an Area Property coverage first, then cleaning that coverage prior to converting is faster.

Creating a Cross Section Database from Text

A Cross Section Database can be created by extracting data from feature arcs, manually entering cross section data within a project, importing the cross section data from a spreadsheet, or by importing the data from specially formatted text file. When importing data from a text file, please keep in mind the following:

• Import the data as Feature Data
• Make sure the Cross section coverage option is turned on. A 1D Cross Section coverage must exist.
• The text file must have an XS ID or Station ID column. This defines the points found in each cross section.
• The cross section points in the text file must be in sequential order unless there is a distance column in the text data file.
• A PT column can be used to assign special points. These are used to annotate features such as thalweg, left bank, right bank, left toe, right toe, abutment, pier, and so on.
  • It is not recommended that the PT column be the final/last column in the text data file.
  • Content should be included in the PT column in the first few rows to make sure the import wizard recognizes the column.
  • If the data on the first few rows does not contain a PT type, a dummy PT type can be used to make sure the import wizard recognizes the column.

Interpolating Cross Sections Along a Centerline

When interpolating cross sections along a centerline, please keep in mind the following:

• Both a 1D Cross Section coverage and a 1D Centerline coverage (including a centerline arc) are required.
• All of the cross sections must intersect the centerline arc.
• When interpolating, SMS uses the centerline arc to orient the interpolated cross sections. Keep in mind that interpolated cross sections:
  • Are created from two bounding cross sections in the cross section database.
  • Have an interpolated skew angle to the centerline.
  • Have interpolated bends for each bend in the bounding cross section.
• Orientation is based on the centerline, so it is recommended that the centerline be smoother than the desired cross section spacing.
• At least two adjacent cross sections must be selected before initiating interpolation by right-clicking in the Graphics Window and selecting Interpolate Cross Sections.
• When specifying the spacing option, it can be either a specific distance or a specific number of cross sections between each pair of bounding cross sections.
• If points should be excluded from the interpolation, be sure to specify them in the Excluded Features dialog.
  • Examples of points that might be excluded include pier locations or water surface points.
  • Examples of cross sections that might be excluded include those with specific point types (such as bridge cross sections).
• After interpolation is completed, a report dialog will appear. It includes information such as how many cross sections were created.

Trimming Cross Sections to Annotation Type

When trimming cross section to annotation type, please keep in mind the following:

• A 1D Cross Section coverage must exist, and it should have feature points identified (such as bank arcs).
• Right-clicking after selecting the desired cross section and selecting Trim Cross Sections to bring up the Excluded Features dialog. This dialog allows selection of the trimming points for each end (left and/or right) of the cross section.
• When a trimming point type is selected, the point of that type closest to that end of the cross section will be used.
• After interpolation is completed, a report dialog will appear. It includes information such as how many cross sections were created.

Converting Cross Sections to a 2D Scatter

When converting cross sections to a 2D scatter set (TIN), please keep in mind the following:

• Right-clicking on the coverage containing the cross sections and selecting Convert to | Map→2D Scatter brings up the Map to Scatter dialog.
• This dialog allows selecting the Database option and specify any points or cross sections that should be excluded.
• Any breaklines connecting similar classification points on adjacent cross sections will be honored and created. This includes breaklines for thalweg, channel toes, and so on.

Creating a Centerline Coverage from Annotated Cross Sections

When creating a centerline coverage from annotated cross sections, please keep in mind the following:

• This tool is accessed by right-clicking on the cross section coverage and selecting Generate Centerline Coverage from the menu.
• Using this tool creates a centerline and bank arcs interpolated from the thalweg and bank points on the cross sections.

Using HEC-RAS Cross Section Data

When using HEC-RAS cross section data, please keep in mind the following:

• The HEC-RAS project used must be georeferenced.
• The GIS data must be exported from the HEC-RAS project, creating a "**RASexport.sdf" file, where the "**" is the name of the project.
• The exported data must include bank points to allow for trimming of the cross sections.
• The exported data must include a centerline to facilitate interpolation. If a centerline is not included in the exported data, one can be created after the exported HEC-RAS data is imported into SMS.

Related Topics

• Editing Cross Sections