Checking Your Surfaces For Evident Defects

When you create a surface model in TBC - whether it be a TIN Model made from Points and Lines or a Corridor Surface Model or a Vertical Design Model etc. they all end up as a TIN model for graphical display purposes.

The TIN Model when it incorporates breaklines and points creates 3D faces, and those 3D faces are divided into groups for shading purposes based on the breaklines that you have in the model. Where there are no breaklines separating triangles, the colors and shadows in the model are graduated between the faces to give a “smooth shading” effect, however where there are breaklines the shadows are sharply contrasted across the breakline provided that the Surface Sharpness properties of the line are set to Sharp or Sharp and Texture Boundary. If that property is set to soft, then the shadows will be smoothed across breaklines.

So the effects of lighting and shadow on a surface can rapidly reveal defects in your models and should not be overlooked as a gross error check in your surfaces - the defects will literally stand out as a sore thumb where they exist.

Quick QA Review of Surface Models

Open the 3D View and set your view filter to show the surface that you are validating. In the surface properties you can set the coloring in 3D to be by surface color (single color that is derived from the surface color setting) or color by elevation (sets up color bands). Color bands will highlight spikes and holes and also will show surface irregularities.

Set your Transparency on the surface to 0
In Plan and 3D view set Show Shadows to Yes
In Plan and 3D view Set Show Slope Arrows to Yes
Set the Display Flags to Yes
In the Plan and 3D view Set Shading to by Surface Color or by Elevation
In Plan and 3D view you probably want to show the wireframe (Triangles) and the Breaklines and Drapelines - so you can clearly see the model elements.

Surface Edge Checks

Check your surface edges - make sure that you have cleaned out edge triangles that are not needed. Use Trim Surface Edge Triangles (Right click menu after selecting a surface) to clean the edges. Then use Create Surface Edge Breakline to put a boundary around the outside of your surface to lock it in. You can use the Maximum Edge Length property of a surface to limit the edge triangles to some degree. If your surface is fully edged by breaklines already (eg for a Road the daylight lines left and right and a line across the open ends of the road - if collectively they form a continuous line then they will naturally constrain the surface. Note if any point or line end is outside the edge breakline(s) and is 3D and is included in the surface then it will break the boundary and make it invalid.

Flat Triangle Checks

Typically set your Adjust Flat Triangles to Yes and set a tolerance of at least 1’ but you can make this number as large as you want it to be (typically used for modeling from contours) - this will drive triangles to form between contours rather than across a single contour (typical use in stockpiles, ponds, dams, hill crests and swales to improve modeling from the contours).

Triangulation Checks

Check your triangulation - a good surface has good triangulation - in “uniform areas” you are looking for uniform triangulation - well spaced and a triangulation that generates a good surface that represents the intent of the engineer. Use Project Settings - Computation - Surfaces - Breakline Approximation parameters to control the density of your triangulation around curves and along straight sections of lines. Add extra breaklines to the surface to improve the triangulation. Typically I use 0.02’ for horizontal and vertical tolerance and 10’ as my start point for line inclusion in surfaces. If I need to change that on specific lines I use the Override Segment Length function to change the density of triangulation on a single or selection of lines to get the model that I need. Remember too many triangles can be as bad as too few triangles when building models for machines. A machine blade is a fixed width and so having triangles that are narrower than a machine blade that change the shape of a surface cannot be graded by an operator.

Shape and Consistency Checks

Exaggerate the surface in the 3D view to check its shape and consistency - an exaggerated view can highlight problems you cannot see at 1:1 exaggeration, but it can also make you think you have an issue where you really don’t so use it wisely. (CTRL + SHIFT + Wheel in 3D View or Section / Profile View changes exaggeration)

Lighting Checks

Use the 3D View Settings command and enable sun lighting - then you can change the lighting month from Jan to December - in the Summer months the lighting is at a higher angle than the winter months, and then the time of day moves the lighting source from East to West. By manipulating the lighting on a surface you can highlight warts in the surface that you may have missed e.g. lines with gaps between end points or lines that overlap or have mismatched elevations, points that are a little high or low, or where triangles on near vertical faces have not formed correctly.

Flags and Warnings

Check for Flags and check your flag tolerance - Project Settings - Computations - Surfaces - Minimum Warning Distance - set this at a point where you care about errors in your surfaces - i.e. if 0.01 is not an issue for you set it at 0.02 - that way very small errors will not be flagged. A flag is where you have height busts in the model - typically where you have two points or two lines or a point and line in the same XY location (within TBC point Tolerance (typically 0.1mm) but have different Z values. TBC always uses the lower of the two or multiple options and flags the others in the surface flags pane (Flags Pane can be turned on using the Flag icon button that shows up in the toggle bar at the base of your screen when you have flags on your surfaces). Double Click a flag in the flag pane to center the plan view on the flag and review the errors associated. Use Nudge Line to move lines or nodes on a section to fix flags or edit the crossing lines etc. to resolve Flags in the way that you see fit.

Surface Slope Checks

Check surface slopes using the surface slope arrows. If your triangles do not all show a slope arrow - you can change the min length of slope arrows in Project Settings - Computations - Surfaces - Slope Arrow Length to make it smaller so that more triangles show their arrows. Use the arrows to verify slope directions, water drainage (toward inlets and away from buildings and to avoid pooling / flat spots where there are no inlets or drainage structures etc. Make sure that water will flow towards the edge of pavement and up or down the road in the gutters and flow into inlets / structures as designed.

Grade Checks

Check the grades on key flow line elements by using the Profile Viewer on the lines. This will show you the way that water will flow along those lines - again check for flat spots and pooling areas or slopes that are too shallow / steep.

Cross Section and Profile Checks

Check quick sections across surfaces to make sure that you have the correct slopes and that your triangulation is not causing slope errors - if your triangle density is too low - you will have increased chording of the model and that will lead to slope breaks and slope errors that should not be there. Use the surface slicer views or cross section editor or corridor template editor / sideslope editor to check and validate your model slopes.

Elevation and Slope Spot Checks

Create a QA layer in TBC and then define Smart Text that computes surface elevations and maybe offsets elevations for a subgrade adjustment or top of curb (from pavement elevation) and then click any spot that you want to check. This can be used to also check the surface slope at any location that you click as well as things like station and offset checks on check points. The Smart Text spreadsheet (available to All Tools subscribers) has all of the smart text functions laid out with use case examples. You can also use Smart Text to QA structures (rim Elevation, Invert Elevation and structure heights etc.) Place all the QA checks on your QA layer as a visual check and also a QA reference to show where and how well you checked the model.

3D Drive Around

If you want to “drive around the site” using a fixed view perspective then use the 3D drive View on the surface and use a range pole or vehicle to show you the location that you are viewing in 3D in the plan view. Having a constant perspective on a model can also highlight other issues that may be hard to see otherwise - bumps or sags may show when you drive the vehicle over an area etc.

Other Cosmetic Checks on your models

Check your layer setups and Layer Naming conventions - keep them clean and well organized and make sure that your final model is to your internal standards

Object Naming and Naming Conventions - If you intend the models to be used by field crews - naming your objects in a consistent way helps them - run checks on all the lines and points in the model to make sure that they are named and named to your conventions

2D and 3D linework - For staking positions of geometrical shapes - you should provide 2D linework in a DXF or DWG format - this means that a field crew can accurately stake anywhere on the lines and get it right. DXF and DWG formats do not support 3D curvilinear features well - typically curves will be chorded and that means unless the field crew stakes the chord points - they can get the position wrong (depending on the degree of chording you allow in your models. They also cannot determine radius values or centers of arcs or curves from a chorded model.

Colors - Field systems have a white or black background. Some colors are hard to see in sunlight on a light or dark background. Make your models with colors that work for field crews (Machines or Rovers).

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