Global Mapper to Revit Workflow for Aerial Data

This workflow assumes you have a cleaned up DTM GeoTIFF surface, and a matching GeoTIFF aerial mosaic image.

Revit has no understanding of coordinate systems and works in millimetres.

Creating the Workspace

Revit runs into accuracy/rendering issues when data is more than 16km from the origin, so all exported files will have to be centred about the coordinates 0,0. We do this by performing a shift to all layers in Global Mapper.

1. Open a new Global Mapper workspace. This will be used only for creating and exporting data to be used in Revit.

2. Import the GeoTIFF DTM and mosaic image into Global Mapper

3. Import your control points – these will be used to shift the entire survey to be centred about the workspace’s origin.

4. Find the X / Easting and Y/Northing coordinates of the control point you wish to be at 0,0.

5. Select all layers in your Global Mapper workspace in the Control Centre > Right Click > SHIFT – Shift Selected Layer(s) a Fixed Distance or Transform Coordinates…

6. In the Select Transformation Type window, select Shift Layers a Fixed Distance from the dropdown (it should be automatically selected) and click OK.

7. Select the Specify Offset as Fixed X/Y Distance Offsets radio button and enter the negative X/Y coordinates of your control point from step 3 and click Apply, ensuring the Units dropdown is set to meters.

8. Click Close when done.

Your layers are now centred about the origin, with your desired control point at 0,0.

Creating a Bounding Box

Next, we’ll create a bounding box for positioning of the image in Revit.

1. Right click on the aerial mosaic image layer and select Layer > BBOX/COVERAGES – Create Layer Coverage Box/Polygon Area Features.

2. Click Yes to Create Rectangular Areas.

3. You will now see a Rectangle on a new layer in your Global Mapper workspace.

Exporting Files

Next, we will export all required files for Revit.

Exporting the Aerial Image Bounding Box

1. Right click the Bounding Box polygon you created from the mosaic image and click Layer > EXPORT

2. Select DXF from the Select Export Format dropdown.

3. Tick the Use Legacy DXF Exported checkbox – Some programs run into issues importing DXFs if this checkbox is not ticked.

4. Tick the Generate Zero-Width Lines checkbox.

5. Click OK to export the DXF file.

Exporting the DTM as a CSV file

1. Select either your DTM GeoTIFF or DTM points file layer(s) and right click > Layer > EXPORT

2. Select CSV from the Select Export Format dropdown.

3. Under Field Separator, select Comma (,)

4. Under Coordinate Formatting, tick the Include Elevation Values for Each Point (If Available) checkbox. Leave all other checkboxes unticked.

5. Under the Coordinate Column Names section, ensure X/Y/Z column names are set to the correct X/Y/ELEV properties.

6. Under Attribute/Field Options, ensure only the Use UTF-8 Encoding for Text Values checkbox is ticked.

7. Click OK to export your DTM .CSV file.

Note: Revit does not handle large points files well when creating Toposurfaces. It is recommended to create a CSV with as few points as possible.

Conclusion

You will now have the following deliverables for use in Revit:

• CSV file containing XYZ coordinates

• GeoTIFF image. Revit will import this as-is.

• DXF containing a rectangular bounding box, to be used when scaling/positioning the image in Revit.