The photos are taken digitally, which can be further improved or enhanced. The degree of detail is restricted to pixel resolutions of the sensors.
On the other hand, Aerial photography snapshots are taken by cameras and photographic films from an altitude of a few thousand meters. The images are an analog record, so no further improvements are possible after obtaining the photographs. The photographs have a very high degree of detail. Remote sensing satellites are capable of collecting large amounts of data in a relatively limited time frame. The advantage is that the more modern the satellites, the faster they lock on an area and take photographs.
The sizes of the pictures are enormous as they allow a complete site to be captured in a small time frame and using fewer images. Whereas, Aerial photography used to be a slow and time-consuming process.
The size and shape of a geographical area to be captured determined the amount of time taken. Using airplanes to fly back and forth led to a series of overlapping photographs being taken. Despite this, modern cameras have made the process faster as data strips are recorded rather than individual frames.
Remote sensing has an advantage in that satellite imagery of a particular location in the world can easily be obtained once a satellite is positioned. While in aerial photography , there is delayed surveys and image attainment depending on the location of the study. The surveying team has to be in the study area to ensure a weather window is not missed.
Stereo imagery is usually not included in satellite image capture and the generation of other value-added products usually relies on external data sources. A big advantage of using aerial imagery is the flexibility to plan data acquisition according to the local weather conditions and take every opportunity to fly in cloud-free conditions.
It is also possible to fly under cloud cover with minor corrections to be applied during post-processing. This guarantees cloud-free data delivery. Due to low altitude acquisition, aerial data does not suffer from atmospheric effects which can impact the quality of data in satellite imagery. Apart from SAR synthetic aperture radar satellites which can acquire data regardless of cloud cover and illumination conditions, most satellite providers do not guarantee completely cloud-free imagery.
Cloud free coverage, especially in the tropics, can be very difficult to obtain. Corrections also must be applied to remove atmospheric effects and haze. With improved quality of large-format digital aerial cameras, airborne GPS and post-processing techniques, the absolute accuracy of aerial imagery is getting better and better.
A typical horizontal accuracy of two pixels can be expected for aerial imagery. High resolution satellites location accuracy is usually around 10m to 20m without ground control points, but this value is improving with new satellites coming up. With a network of GCPs the accuracy can be improved to a few metres. With the development of new large-format cameras, it is possible to acquire a large amount of data with a minimum number of runs. The processing time will depend directly on the number of frames but with advances in computing technologies such as cloud computing, processing time is decreasing.
Aerial acquisition allows the capture of time-sensitive events as the acquisition team has full control over when the aircraft can fly and allows capture during specific windows of opportunity. High resolution satellites can acquire a large amount of data in a timely manner anywhere in the globe. The images acquired are processed quickly due to their small number.
More satellite constellations are being developed to increase coverage, however, to capture a specific area, a delay of one to three days occurs due to the way satellites orbit the earth. Considering cloud-cover, it can be difficult to capture time-critical events.
The cost of an aerial acquisition survey is not simple and may vary depending on many variables such as mobilisation cost, resolution, accuracy. Satellite acquisition costs are usually more straightforward to calculate than aerial imagery costs. How Does an Infrared Telescope Work? How Do Holographic Projectors Work? How to Use a Meade Telescope. Tools Used in Hydrology.
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