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Topography
Orthophoto Map
A geometrically corrected aerial photograph with perspective and terrain distortions removed, allowing it to be used as a map.
An orthophoto map is an aerial photograph or satellite image processed to remove geometric distortions caused by camera perspective, terrain irregularities, and Earth curvature. The result is an image with uniform scale throughout.
Orthophoto properties:
- Constant scale - uniform throughout the image
- Geometric accuracy - distances and areas can be measured
- Coordinate reference - each pixel has coordinates
- Photographic detail - realistic situation representation
Orthophoto resolutions:
- 50 cm/pixel - satellite images, large areas
- 20-25 cm/pixel - standard aerial photography
- 10 cm/pixel - detailed orthophoto
- 2-5 cm/pixel - drone orthophoto, construction sites
Orthophoto creation process:
- Acquisition of aerial or drone imagery
- Ground control point (GCP) measurement
- Photogrammetric processing
- Orthorectification (distortion correction)
- Mosaicking (image stitching)
- Color balancing
Orthophoto applications:
- Spatial planning - existing situation analysis
- Cadastral surveying - boundary verification and agreement
- Construction control - change monitoring
- Agriculture - field area control
- Environmental monitoring - observing changes over time
- Cartography - map updating
Latvian orthophoto maps:
- LGIA provides national orthophoto map
- Regular updating (approximately every 3-4 years)
- Available on Latvian Geospatial Information portal
- Can be used as background for topographic plans
Orthophoto vs regular aerial photo:
Unlike regular aerial photo, orthophoto is geometrically accurate - objects are in correct positions and measurements can be made directly from the image.