Connecting Drone Survey Data to Civil 3D and InfraWorks

In my previous blog post, I discussed how to use ReCap Photo to generate a 3D model from photos taken during a drone site survey.  Just having the 3D model is not good enough, you need to be able to get it into your design tool, whether that is Civil 3D or InfraWorks.  That is what I would like to cover in this post.

Once I learned that ReCap Photo was mesh-based, I began to wonder, "Are meshes better for use downstream?"  I tried taking the mesh files into Civil 3D and InfraWorks to see how they worked.  Based on that experience, I would say that RCS and RCP files, which are ReCap point clouds, are the better choice for output from ReCap Photo.  That is why I will always choose for ReCap Photo to generate an RCS file when creating the project.  It is not mandatory to create the RCM, but I typically do that out of habit.

Once the project is done calculating in the cloud, it can be downloaded.  Hovering over the thumbnail for the project will allow you to download, or delete the model if necessary.

This will download a folder containing files and/or zip files of the output files that were chosen during project creation.  If the goal is to take the model into Civil 3D or InfraWorks, the user can extract the data from the RCS.Zip file.

The next step is up to the individual user, you can go right into your design tool or go into ReCap to do some cleanup.  If you take the RCP file into ReCap first, you can delete stray points or classify points into regions, such as site, building, trees.  The benefit of regions is that they essentially become layers that can be turned off or on when you get into Civil 3D.  Deleting points versus creating regions have their pros and cons and it is up to the end-user to decide which approach they would like to take.  My personal preference is to take the output file into ReCap and create regions.

If you have chosen RCS as an output type, the download will contain a zip file with .RSC.Zip at the end.  If you extract that files, you will find an RCP file, which can be opened in ReCap.

Once the model is opened, it is just a matter of selecting points and then deciding to either delete them, classify them into a region, or cropping based on the selection.

After any necessary cleanup, it is possible to insert this model into InfraWorks and Civil 3D.

In InfraWorks, the point cloud can be added to a model as a data source.  From the Data Sources menu, you just have to select Point Cloud from the Add File Data Source drop-down.

Once the Point Cloud has been added, it will need to be configured.  Since the point cloud should have the correct geolocation, it should land in the right spot.  However, I have noticed that the elevation of the point cloud can be a little lower than it should be, so it may be necessary to tweak the Z offset.

Here is an up-close look at the model with the point cloud.  You can see the building footprint brought in from OpenStreetMap, which can be deleted if necessary.

In Civil 3D, the workflow for connecting to a point cloud has not changed at all.  There is one small difference though.  In Civil 3D there has always been a command for attaching a point cloud.  However, Autodesk has added RCP and RCS files as possible choices for the Attach command.  In the end, regardless of which command you use, the workflow for point clouds is the same.  You just have to select the point cloud file to attach, then you will have the ability to specify the insertion point, which I typically leave as 0, 0, 0 because the model should be properly geolocated by ReCap Photo.  If you need to tweak the elevation, you can do that by changing the Z value for the insertion point.

A potential next step would be to create a surface from the point cloud.  This tool has been around since AutoCAD Civil 3D 2015 as an extension tool, then was added to the standard tools inside of Civil 3D.

Using this tool, a user can create a surface from an entire point cloud or just selected points.  The biggest element of this process is the filter settings.  I always pick the Kringing method, just because it seems like the best option when compared to Planar Average and No Filter.

Here is an example of a surface I created from an attached point cloud.

Once created the surface from the point cloud can be used just as any other Civil 3D surface.

Here is a video demonstration of the workflow for InfraWorks and Civil 3D.


Both of these workflows can be beneficial it is just a matter of which product you need to place your point cloud.  When ReCap Photo was introduced, I was nervous that I lost part of a great workflow.  It wasn't lost, it was just a matter of I didn't know how to access the point clouds that were generated by ReCap Photo.  Once I found where to access them, I began to appreciate how simple it is to access them.

Using ReCap Photo for Drone Site Surveys

In my job, I need to stay up on the current software, and associated workflows.  One software that has changed greatly over the last several years has been ReCap, and its companion software ReCap Photo.  In the early versions, ReCap had two workflows, one for scans and one for photogrammetry.  You might be aware that a few years ago, Autodesk split the two workflows, keeping scanning in ReCap and introduced ReCap Photo for photogrammetry.

In a previous blog post, I wrote how to take photos of an object and generate a 3D mesh.  Another application for this technology has been using drone photography to aid in site surveying.  One of my first ReCap projects was working with a customer and Autodesk to generate a Civil 3D surface from drone photographs.  

Since the introduction of ReCap Photo, I haven't really used the site survey workflow, especially connecting a model to Civil 3D.  So I wanted to see how the process has changed, some of it is the same, but there are a lot of great additions.  I learned a good bit and wanted to share that through this blog.  I did try to create my own data set, from my own drone photos.  However, I am sad to say that my drone just doesn't work well for this type of application, so I will have to use a generic dataset  I got from Autodesk.

The whole workflow starts from picking the type of project, Aerial or Object.  Creating an Object project is my normal workflow, and just allows you to add photos.  Using Aerial gives you a lot more options, which are all centered around geolocating your project.  

After picking your project type, the second step remains the same, selecting your photographs.  One way this workflow is made easier is that if the photos have a geotag in them, ReCap Photo is capable of reading that information and use it while generating the 3D model.  One oddity that I have run into is that I will get a message warning me that not all of my photos have GPS data, so my model will not be geolocated.  However, the 3D model does come out properly geolocated.

One significant change for the better is that ReCap Photo has changed the way that Ground Control Points are handled.  After your photos are selected, you can select an icon on the left of the screen to open a different window to enter the Ground Control Point data.

In the Ground Control Points window, you can designate the Coordinate System for the Ground Control Points, you can enter their values, or load them from a file.  Once the points are loaded, you can then select a row and identify the point in your photographs.

Another useful function of this interface is to toggle the display from Photos to Map.  That will then change the right side of the window to display a Bing Maps image of the site.  In my case, since my photos are geotagged, ReCap Photo will even display camera glyphs at the locations the photos were taken from.

Once all the Ground Control Point data is entered and identified in photos, you can return to the previous screen by clicking Done at the bottom of the window.  This will take you back to the photo selection screen, where you can select Create to start the project creation.

At this point, the user just has to enter a name for the project, decide on the output files, and pick a target coordinate system.

There are three possible output files, the user can select one or all three.  The RCM file is a mesh file and would be suitable for continuing to work in ReCap Photo.  The RCS output type is a point cloud and is the best type to be placed into Civil 3D or Infraworks.  The Orthophoto and elevation map options generate 2D TIFF output.  My personal habit it to generate the RCM and RCS.

For the Target Coordinate System, ReCap Photo will default to a UTM Zone.  However, I have found that those don't typically locate properly in Civil 3D or InfraWorks.  For that reason, I always change the coordinate system to the appropriate State Plane.

You will also notice that creating this model will consume a specific amount of Autodesk Cloud Credits.  ReCap Photo determines how many Cloud Credits the project will cost based on the number of photos in the project.

After defining all the selections for the output, it is just a matter of submitting the job and waiting for the 3D model to be generated.

Here is a video demonstration of the process.

I like the new additions, I think that they give you better control over the ground control points, it is easier to set the coordinate system and the output options are easier to work with.