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What is an Orthomosaic Map and How is it Made?

17 Jun 2025 Trishunya Team
What is an Orthomosaic Map and How is it Made?

What is an Orthomosaic Map and How is it Made?

If you have ever seen a high-resolution aerial image of a project site where every pixel has a real-world GPS coordinate attached to it, that is an orthomosaic. It is not just a photo. It is a geometrically corrected, spatially accurate map that you can measure distances on, overlay with design drawings, and use directly in GIS software. It is one of the most useful deliverables a drone survey produces.

3cm/pixel
Typical ground resolution
500+
Photos stitched per km²
5cm
Horizontal accuracy

The Difference Between a Photo and an Orthomosaic

Regular aerial photo
  • Perspective distortion at edges
  • No geographic coordinates per pixel
  • Cannot measure distances accurately
  • Cannot overlay with CAD drawings
  • Scale varies across the image
Orthomosaic map
  • Geometrically corrected, uniform scale
  • Every pixel has real GPS coordinates
  • Measure distances directly in GIS
  • Overlays perfectly with design drawings
  • Usable as base map in ArcGIS, QGIS, AutoCAD

How an Orthomosaic is Made

Drone flight with 75-80% image overlap
High overlap ensures every ground point is captured from multiple angles for accurate 3D reconstruction.
GCP tie-in for georeferencing
Ground Control Points with known DGPS coordinates anchor the mosaic to real-world coordinates.
Photogrammetric processing
Software (Metashape / Pix4D) identifies matching features across thousands of overlapping images and builds a 3D point cloud.
Orthorectification and mosaicking
Perspective distortions are removed from each image, then all images are stitched into one seamless map.
Export as GeoTiff
Final output is a GeoTiff file with embedded coordinate system, ready for GIS and CAD use.
Photogrammetry software processing drone images to create orthomosaic map

Photogrammetric processing in progress. The software identifies thousands of matching feature points across overlapping images to build the 3D reconstruction.

What is an Orthomosaic Used For?

Urban planning base map Solar park layout Land use mapping Construction monitoring GIS data input Feature extraction

Any project that needs a current, accurate visual base of a site can use an orthomosaic. For solar parks, the orthomosaic feeds directly into layout software for panel placement optimisation. For urban planning, it replaces outdated satellite imagery with fresh, high-resolution data. For transmission line projects, it provides the corridor visual base for all further analysis and design.

Orthomosaics are delivered as GeoTiff files that open in ArcGIS, QGIS, Global Mapper, AutoCAD Map, and Civil 3D without any conversion. If you are working with spatial data and you do not have a current orthomosaic of your project site, you are working blind.

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