Aerial versus satellite imagery
Aerial and satellite images are both rasters, but they are collected differently and usually solve different problems.
| Characteristic | Aerial photography | Satellite imagery |
|---|---|---|
| common strength | very high spatial detail | repeated wide-area capture and spectral bands |
| typical public NZ scale | centimetres to decimetres | metres to tens of metres, depending on sensor |
| revisit | survey/project based | regular orbital repeat |
| clouds | flight can often be planned | optical sensors may lose scenes to cloud |
| spectral capability | often RGB; sometimes NIR/multispectral | frequently multispectral; radar also available |
Spatial resolution
Ground sample distance describes how much ground one pixel represents. A 10 cm orthophoto pixel is not automatically accurate to 10 cm. Positional accuracy also depends on camera geometry, control, terrain model and orthorectification.
Temporal resolution
Temporal resolution is how often a sensor can observe the same area. This is why moderate-resolution satellites are useful for vegetation, flood and land-cover monitoring even when aerial photography has much finer pixels.
Spectral bands
True-colour imagery uses red, green and blue roughly as our eyes see them. Multispectral sensors can also record near-infrared, short-wave infrared and other wavelength ranges. Combining bands differently can reveal vegetation vigour, moisture, burn scars, sediment or water/land contrasts that are difficult to see in RGB.
Optical versus radar
Optical imagery records reflected sunlight and is affected by cloud. Radar sensors transmit microwave energy and measure its return, allowing observations through cloud and at night. Radar interpretation is less visually intuitive than a photograph but is powerful for floods, deformation and surface structure.
Orthorectification
An orthophoto has been corrected for camera/sensor geometry and terrain so it can be used as a map at its stated positional accuracy. A raw historical aerial frame is not an orthophoto simply because it has coordinates attached.
Use both
A strong change study might use a 1940s aerial frame, a 1980s orthophoto, a 2025 LINZ aerial survey and a Sentinel-2 time series. The different sources provide different forms of evidence rather than one continuous perfect record.
Continue to Compare change over time.
Last reviewed: 26 August 2026