Start – Image import with GCP based orientation
Welcome to 3Dsurvey tutorials.
This tutorial shows how to start your project and demonstrates the workflow from importing images and orientating your model using ground control points (GCP) to generating a point cloud and calculating an orthophoto.
This scenario applies if you’re using images with no GPS or any other geo-locating data and have to orientate your model using ground control points.
Start by opening 3Dsurvey, go to Images -> Load images -> find your project folder (prepare it before you start with the project), select all images -> click Open.
Telemetry Importer pops up but remember, this time we have neither telemetry nor EXIF, meaning we don’t need to select or import any geo-data file. Click Skip.
The list of images appears in the right pane of your screen. Next, click Bundle adjustment button. In the pop-up window set your parameters: check ‘Global’ box, set your flight height, leave ‘Guided feature matching’ box unchecked, ‘Feature extraction mode’ to Normal and click OK.
Next we need to orientate the model. Click Orientate button -> select ‘orientate with GCP data’ option. Click Browse in the next window, find your coordinates .txt file and click Open to get a table with your x, y, z info. Click Next.
Find 3 random GCPs (targets) that you positioned when surveying at the location. Click with a right mouse button for the point to select and colour in orange. Upon selecting 3 points the software will automatically find all the other control points and colour them all in green. Click Next.
In this step you can manually correct your control points’ selections in case anything is off-centre or incorrect. Left mouse click to move/re-centre a particular control point, double-click to ignore/exclude from orientation process. Click Next when pleased.
Next the Orientation summary pops up for you to review the numbers. Click Finish and go to the next – Reconstruction.
Click Reconstruction button and set the parameters. ‘Reconstruction level’ to High, ‘Minimum image overlap’ to 3, ‘Optimize point cloud’ box checked. Click OK. Give 3Dsurvey a little time to reconstruct the model, reconstruction for 50 images takes about an hour…
Next we get a generated dense point cloud. To calculate a digital terrain model and then orthophoto, click Classification button to set some of the basic parameters. Default parameters work with 99% of cases, simply click Next.
Wait for it to process, then in the 1st step select some of the bigger terrain patches and areas to determine what your terrain is. The software will automatically populate your selection based on parameters you set in the previous step. Click Next.
In the 2nd step you get your point cloud classified, click Finish if all is ok, otherwise correct your selection.
Back to main 3Dsurvey window, double-check your model and click ‘Delete other’ button to remove all unwanted objects and obstructions. Press ESC key to deselect your model.
Navigate to DSM -> Calculate new -> set parameters (Grid cell size: 1m, Hole fill interpolation: All, Smoothing size: 3 cells. These work best for orthophoto generation) and click Calculate.
A calculated digital surface/terrain model comes on, all we need to do is to generate our orthophoto.
Navigate to DOF -> Calculate new -> set parameters. Normally all the presets work great, change whatever doesn’t work for you, click Calculate.
And there you go. You’re left with a perfectly calculated Digital Orthophoto with realistic colours and survey-grade accuracy.
Check other tutorials to learn what to do from this stage on. How to customize, measure 3D and calculate volumes, generate contour lines, profiles, how to generate reports, geodetic documentation and presentations for your clients.