3.2 . Image Market
In the future, three different data sources have to be reckoned with in the photogrammetric
image market:
- High-resolution earth observation satellites
- Digital airborne cameras
- High-resolution analog aerial mapping cameras
This competition and new technical capabilities will lead to drastic changes in the availability
and price of image data in the coming years. Satellite image data are already being collected in photo
data bases and sold as required through e-commerce over the Internet. Not only the pure image data but
finished products are also offered. In addition to orthophotos there are complete information packages
containing image data with evaluations as well as weather information e.g. for use in agriculture.
Table 1 : Future Applications of Airborne Imagery
| Application |
Description |
| Mapping |
City and county governments, cartographic departments, remote sensing companies; photo scale 1:5.000 - 1:50.000 |
| Construction |
overground + underground building, facility management, supply lines, small events; photo scale 1:3.000 - 1:7.000 |
| Infrastructure |
route planning and monitoring of pipelines, railways, streets, corridor applications; photo scale 1:3.000 - 1:7.000 |
| Telecommunication |
3D-models of the city buildings |
| Agriculture |
monitor crop yield, soil, stress, and impacts of pests and disease |
| Forestry |
monitor tree yield, tree trimming, fire |
| Insurance |
high resolution data in a very short time e.g. height resolution 0,1 m for flood monitoring |
| Disaster Management |
quick reaction within hours |
3.3 . Image Market Trends
- Shift from "Performance Enhancement" to "Affordability Improvement"
- New methods for distribution; e.g. direct sales via the Internet
- New services for the consumer market; e.g. satellite images on CD-ROM
- Low-cost geo-coded image data
- Preprocessing of image data is a challenge for photoflight companies
- Image data will become a commodity
These trends in the image market have different effects on aerial applications. New thematic
applications will arise in the field of remote sensing. The demand for low-cost color orthophotos will
also rise because of the satellite images and new distribution channels offered by the Internet. Classical
photogrammetric applications such as stereoplotting of aerial photography and the production of terrain
models will shrink because of the competition with other measuring methods such as laser scanning or
other space-borne image data sources.
4. Requirements Airborne Digital Cameras
This analysis of the image market indicates the demands for digital airborne camera systems.
To complement high-resolution satellite images, a ground resolution of better than 1.0 m and multis-pectral
features of approx. 450 to 900 nm are required. A special competition will arise between film
based aerial mapping cameras and digital airborne cameras. Both system are being used in planes under
comparable conditions. Compared with the aerial mapping camera, the digital airborne camera offers
- higher radiometric resolution
- reproducible color information
- cost savings for film
- cost savings for film processing
- cost savings for scanning
- immediate availability of the image data
The essential criterion in a performance comparison between aerial mapping cameras and digi-tal
airborne cameras is the geometric resolution. In this field, no digital airborne camera can match an
aerial mapping camera in the foreseeable future. 230 mm aerial film can be digitized with the help of a
state-of-the-art photogrammetric scanner with a pixel size of 7 µm. This resolution would correspond
to a sensor resolution of 32,800 pixels. An uncompressed color image with 12bit information depth
requires approx. 4.5 gigabytes of memory space and a complete roll of aerial film requires 2.7 terabytes.
The yearly taking performance of a modern aerial mapping camera such as the RMK-TOP is some
20,000 photos. This performance would result in approx. 90 terabytes of image data at a resolution of 7
µm. These data apply to the whole process chain. However, money can be made with a digital airborne
camera only if the data volumes involved can be processed economically. Although there is a lot of
progress in data processing technology, a yearly amount of 90 terabytes per camera will not be easy to
process in the near future.
These numbers imply that time isn't and technology haven't matured for a 100% replacement
of aerial mapping cameras. The question of the pixel numbers required of a digital airborne camera
cannot be answered by comparing frame formats and pixel sizes only. When flying along linear objects
such as roads, utility lines or coastlines, the 230 mm film format of an aerial mapping camera is not
fully used. In spatially limited applications the data volume and the image quantities are also limited. In
these applications it is possible to use digital cameras economically already today. The definition of the
most economic digital resolution depends on the application. The user will accept digital technology
only when this offers an advantage over existing systems from an economical viewpoint. For this pur-pose,
the entire process chain starting from the flight planning up to the finished product in the form of
a map or orthophoto must be analyzed (Heier,1999).
