Data Processing Workflow

Disclosure: Aerotas is in the business of processing aerial data for land surveyors. While this guide is an honest attempt to provide valuable, non-sales focused information to surveyors, we may occasionally refer you to some of our product offerings.

If you are interested in what Aerotas can do for your business, we would encourage you to learn more about our product on our Linework page, or request a quote for a specific project you are working on.

Thank you for understanding!


Purpose

Deliverables

The purpose of this workflow is to go from drone photos to land survey deliverables in CAD. This means a single CAD file that contains

  • Topography / 3D Surface – A 3D surface in CAD that is cleaned of noise, artifacts, vegetation, vehicles, or anything that shouldn’t be in a final surface. The topographic data should be identical to what a surface would look line from a ground survey, and include contour lines, spot elevations, and breaklines where necessary.

  • Planimetric Features – All visible 2D features should be marked as what they are. This includes roadways, curbs, utility panels, building footprints, fences, walls, water features, vegetation, and anything else that can be seen from the air.

  • Orthorectified Imagery – The final orthorectified photo should be accurate, and properly georeferenced and imported into the CAD file.  Further, it should be in a format that imports and functions properly in CAD.

To download a sample of what the final deliverable should look like, check out Aerotas sample projects below.

If you are looking for something OTHER than land survey deliverables, then you are probably in the wrong place. Drones are capable of a lot of things, from real estate photography to racing. But every drone mission ought to have a purpose, and the purpose of this guide is to use drone data for land surveying.

Accuracy

Final deliverables aren’t worth much if they aren’t accurate, so that is the single most important factor throughout this workflow.  If a process compromises accuracy, then it won’t be included in this workflow.

Usability

There are many file types that may be rich in data, but can’t be used easily in CAD. Many very large files, like point clouds or full resolution orthophotos, are so large and cumbersome that they can’t be imported or manipulated in CAD without causing problems. This workflow is designed to get to files that can be used easily and without adjustment in CAD.

The Workflow

Below is the high level series of steps.  Click on each step to learn more.

  • GNSS Post-Processing (Optional) – If you are using airborne RTK or PPK data, then you have to process that data before the geolocation can be imported into photogrammetry software.

    • Output Files: csv of photo locations

  • Photogrammetry – The process of combining photos, geolocation data, and ground control / check points to create a rich 3D model of a site.

    • Output Files: Geotiff orthomosaic and DSM (.tif) and point cloud (.las)

  • Data Extraction – Rich 3D models have far more data than is useful. They need to be cleaned to only the relevant data about the project site.

    • Output Files: dxf

  • Data Finishing – Once the clean data has been generated, it needs to be imported into CAD, merged with the imagery data, and have appropriate layers and symbology applied.

    • Output Files: dwg

  • Quality Check / Accuracy Measurement – Survey deliverables are useless if their accuracy can’t be relied upon.  All files should go through a final QA / QC check, and accuracy measurement before they are considered finished.