Aerial Orthomosaic Segmentation

Project overview

Site-scale drone orthomosaics were segmented into land cover classes across the full survey extent, including the site boundary itself.

Working at mosaic scale changes the failure modes. A single image is a consistent exposure from one moment, but a mosaic is assembled from many passes, so colour and shadow shift across the sheet and a class boundary that looks obvious in one tile is invisible two tiles over.

Work performed

• Reviewed the full mosaic before annotating to establish how each class appears across it.
• Traced the site boundary first so all subsequent work stayed inside the survey extent.
• Segmented vegetation, water and bare ground as continuous regions rather than per tile.
• Followed class boundaries through stitching seams instead of stopping at them.
• Handled exposure drift between flight passes when judging class edges.
• Verified that regions crossing tile boundaries remained single continuous polygons.

What made it hard

• Colour and exposure shift across a mosaic built from multiple flights.
• Stitching seams introduce visible discontinuities through real features.
• Standing water reflects sky and vegetation, changing appearance by pass.
• Sparse vegetation on light soil gives a gradual rather than a sharp boundary.
• The sheer extent of a site mosaic makes consistency harder than accuracy.
• Shadow from terrain and structures darkens whole regions of one class.

Result

A continuous land cover segmentation across the full site, with class regions that hold together across stitching seams and exposure changes.

Final deliverable

Delivered site-wide land cover polygons referenced to the survey boundary, continuous across tiles and ready for area computation.