Working with other topographic formats

As explained in the Topography Compatibility article, only certain types of AutoCAD objects can be selected as topography in Layout Information settings. But there are other formats that can be converted to a usable format. In this tutorial, some options are explained.

TIN Surfaces

TIN stands for Triangular Irregular Network. This is a commonly used type of surface in Civil 3D. In this tutorial, we explain how to convert a given topography (height points) into a TIN surface using Civil 3D. A TIN surface is not a valid topography format for PVcase Ground Mount (compatible formats are explained in Topography compatibility), so we will also explain how to convert a TIN surface back into a usable format in PVcase Ground Mount.

Using Civil 3D to create a TIN surface based on the PVcase Ground Mount imported Terrain (height points)

In the Civil 3D Toolspace go to the Prospector tab, right-click on Surfaces, and select Create Surface. From the Type list, select TIN surface and then OK to add that new surface to the list in the Prospector tab.

Under Definition, right-click on Point Files and select Add. In the newly opened window, click on the + icon and select to open the CSV file generated from Ground Mount. Confirm the point file format selected is correct (usually ENZ) by checking the preview and click OK.

Lastly, use Zoom Extents for Civil 3D to show the TIN surface with contours generated from the cloud point data. 

More detailed information on Civil 3D importing can be found in this Autodesk article.

Many settings for the imported surface can be modified in Civil 3D. For example, the contour line intervals are set by default to 2 and 10 meters, but they can be changed easily to closer/wider intervals by selecting a different Surface style or creating a new one.

Selecting high density for the contour lines in Civil3D would be critical, if the high accuracy of the  exported CSV terrain needs to be maintained. For example, this is necessary if the generated CSV terrain is imported to Civil 3D to make modifications (smoothening transitions, grading roads, etc.), and subsequently needs to be reopened again in PVcase Ground Mount to verify for collision. If low density contours had been used in Civil 3D, then unwanted alterations to the graded terrain could occur.

Converting a TIN surface into a PVcase Ground Mount valid topography format

• With Civil 3D - Contour lines

After reworking a certain terrain in Civil 3D, it might need to be used again in PVcase Ground Mount (for example, as a new Existing terrain for civil analysis). Because Ground Mount doesn't consider TIN surfaces as a valid format for topography, Civil 3D users have the option to use the command ExportToAutoCAD to generate a new DWG file where the TIN surface has been converted to Major and Minor contour lines and can be used as topo in PVcase Ground Mount.

More about how to use this command can be found in this AutoDesk article.

• With Civil 3D - 3D Faces

In order to maintain the highest fidelity for the terrain when converting the TIN surface to a format that is usable in PVcase GM, it is best to use the triangular data (3D faces) from the TIN surface. This can be done by following these steps:

1. Enable Triangle Display:
-Edit Surface Style: Right-click on the surface in the Prospector window, then select "Edit Surface Style". 

-Navigate to Display Tab: In the Surface Style dialog box, go to the "Display" tab. 

-Toggle Triangles: Find the "Triangles" option and make sure its corresponding lightbulb icon is turned on (should be highlighted) to display the triangles. 

-Apply Changes: Click "OK" to apply the changes to the surface style. 

2. Extract and work with Triangle Data:
-Select the Surface: Select the surface you want to extract the triangles from in the drawing area. 

-Surface Tools: Click the "Surface Tools" ribbon panel, then select "Extract Objects". 

-Extract Triangles: In the Extract Objects dialog box, select "Triangles" as the object type to extract. 

-Confirm and Extract: Click "OK" to extract the triangles. 

-3D Faces: The extracted triangles will be represented as 3D faces in the drawing. 

-Further Processing: You can now use these 3D faces as PVcase topography

• Without Civil 3D (in AutoCAD)

If the user doesn't have access to the Civil 3D software, when the file is opened in AutoCAD, the surface will show as an ACAD_PROXY_ENTITY that cannot be used. In some cases, that entity can be exploded in AutoCAD to expose the Contour Lines that can be used in PVcase. Although in most cases that option won't work, in which case the user can try to install a free Civil 3D object enabler as explained in this Autodesk Forum.

COGO Points

A COGO point is a point created by Civil 3D that contains coordinate data and other properties. COGO stands for COordinate GeOmetry.

• With Civil 3D

If a DWG file with COGO points is opened in Civil 3D, those points will not be selectable as topography for PVcase Ground Mount (compatible formats explained here).

Civil 3D users have the option to use the command ExportToAutoCAD to generate a new DWG file where the COGO points have been converted to Block Reference objects (this and other conversion options are explained here). Those Block Reference objects can then be exploded to expose the Mtext objects that can be used as topo in PVcase. 

• Without Civil 3D

When the DWG file with COGO points is opened in regular AutoCAD, those points will show as an ACAD_PROXY_ENTITY that cannot be used as topography in PVcase Ground Mount. In some cases, that type of entity can be exploded in AutoCAD to expose the Mtext objects that can be used in PVcase. Although in most cases that option won't work, in which case the user can try to install a free Civil 3D object enabler as explained in this Autodesk Forum.

GeoTIFF files

GeoTIFF stands for Geographic Tagged Image File Format. This type of file allows georeferencing information to be embedded within a TIFF file.

In the future, PVcase might have an option to directly import GeoTIFF files to be used as topography, but until that is the case, it is possible to use this type of file by simply following these steps:

1. Create a KML file using Google Earth (or any other software that allows for it), with a location matching that of the GEOTIFF file. For example, it could just be a boundary polyline for the site of the project at the same approximate location as the GEOTIFF (although any random object would work).

2. Create a ZIP file that incorporates the newly created KML file and the GEOTIFF file to be imported. This method does not work with TIF files. It needs to be a GEOTIFF file. A TIF file can be converted to GEOTIFF by using ARCGIS or QGIS software.

3. Import the ZIP file using Import AO Data tool as shown in this image:

   
   This workaround makes use of the already existing tool that was developed to import data from the PVcase Prospect site selection software.

4. If the generated contours show flat with 0 elevation (2D contours), it usually means that the real elevations are showing as an attribute of the contours instead of a property of the contours. If that is the case, please follow the procedure shown in this tutorial in order to convert those attributes into property elevations using Civil3D.

5. If a message similar to “GeoTIFF could not be reprojected. Please make sure that the topography is correctly imported" is shown when trying to import the ZIP file, it is likely that the coordinate reference system used is not WGS1984 (global coordinate reference system used worldwide for GPS, navigation, and satellite-based positioning). In that case, conversion to WGS1984 will be necessary, as that is the only system which PVcase GM supports for .tif imports.

Polyface Mesh

A Polyface Mesh represents the surface of an object defined by faces capable of having numerous vertices. It is a common object type for topography. For example, the PVcase Ground Mount Terrain Mesh tool creates a Polyface Mesh based on the selected topography that can be used to understand terrain sloping and create slope restriction areas.

PVcase doesn't allow for a Polyface mesh to be selected as topography for placement of frames. But a Polyface Mesh is composed by grouped 3D Face objects, which are a valid format for topography in PVcase. So it is possible to explode the Polyface Mesh in order to expose the underlying 3D faces that can be selected in Layout Generation Settings.

TXT coordinates

In some instances the only available format for the terrain coordinates is a TXT file with X, Y, Z coordinates. This file format cannot be directly imported to AutoCAD, but with Excel it can be easily converted to cloud point data that can be copied into the DWG file and then used as topography in PVcase Ground Mount. 

The steps to be followed are explained below:

Formatting of the TXT data

1.  

   1. Open Excel, go to File Open, and navigate to the location that contains the text file.

   2. Select Text Files in the File Type drop-down list in the Open dialog box.

   3. Locate the text file you want to open and double-click it. If the file is a text file (.txt), Excel will launch the Text Import Wizard.

   4. In the Text Wizard, select the correct formatting so that the X, Y, and Z coordinates are displayed in different columns.

   5. Once you have imported the data into Excel, add a column to the right of the existing columns, paste the following formula into the first cell: =B1&","&C1&","&D1 (this can also be done by using the concatenate formula).

   6. Expand the formula to all cells and copy all filled cells in this column.

Using the height point data in AutoCAD

1.  

   1. In the Excel sheet copy the cells with the concatenated X,Y,Z values.

   2. Go to AutoCAD and create a point object at 0,0,0 (so that it's easily found) in a new layer (e.g. "0TopoTXT").

   3. Type COPY in the command bar and when prompted select the newly created point.

   4. Next, when prompted to "Specify base point", click the point at 0,0,0.

   5. Now, when prompted to "Specify second point", right-click in the command bar, select Paste.

   6. At this stage, all points from the Excel sheet will be added to the correct positions and elevations.

   7. Now delete the point originally created in 0, 0, 0 so that it is not considered terrain data.