Today, the use of GIS technology is of growing importance for governmental and private economy bodies. A GIS is the main tool for collecting, managing, manipulating and visualizing data, referenced to a certain place on Earth. Already now most of monitoring and decision making processes are not feasible without modern GIS technologies.
However, the power of GIS technologies is limited by the unavailability of geo-data. While in larger scale applications for local governments or for limited areas land survey techniques are preferable, for larger areas (smaller scales), regions or even countries, remote sensing technologies are most appropriate.
RapidEye AG, Germany, launched its own satellite system August 29th, 2008. The RapidEye satellite constellation is the first, and currently the only, operational system that is able to repeatedly image larger areas in short intervals up to 24 hours. With its capability to produce orthorectified imagery with 5m resolution in 5 spectral bands (including a red-edge band), it is an ideal data source for monitoring tasks in the fields of environment, agriculture, and forestry.
The advantage provided by RapidEye is data availability and quality. The Company provides a wide spectrum of services for clients in our core markets: Agriculture, Forestry, Energy and Infrastructure, Spatial Solutions, Emergency Analysis, and Environment. A few solutions will be presented in detail: crop typing, field boundary extraction, crop condition assessment, forest monitoring, and change detection for infrastructure and environmental purposes.
Bring On EO
The RapidEye System + Approach
After successful image acquisition, the data is downloaded to Svalbord, Norway, and subsequential transferred by land-line to the Brandenburg headquarter. Here, the data is subjected to the standard processing of as many as three levels. The highest is level 3, an orthorectified image tile of 25 x 25 km with 5m pixel size, ready to be loaded into any GIS. Optional atmospheric correction can also be applied. The tile size is an internal storing solution. Customers can order data for individual areas of interest and will be charged for the ordered area only.
RapidEye also provides a wide spectrum of value added products and services to its customers, each service being an individual solution for that customer.
For Agriculture...
In addition, RapidEye is currently defining and operationalizing detection methods for further crop types, applicable for certain environmental conditions.
The RapidEye system with its red-edge spectral band is especially sensitive to chlorophyll in plant tissue, which is an important indicator for plant vitality. A repeated visit of plant chlorophyll content allows for the monitoring of the nitrogen nutrition status of plants.
RapidEye specialists use vegetation indices for the derivation of growth curves, which can be used to distinguish crop types and to assess crop condition and growth stages. Once the normal growing behavior of a certain crop type is known, repeated data acquisition enables the specialist to assess the plants status in comparison to what is standard for this particular area. Farmers receive helpful information in order to apply the right measures for optimal growing.
In this context, RapidEye can provide customers with ground cover maps. Such maps reveal what percentage of the ground is covered with green vegetation in various parts of a field. Areas with a lower percentage of ground cover may need special treatment, such as fertilizer application, irrigation measures, and pesticide application.
Ground cover maps offer an overview about plant status, but do not indicate reasons for either poor or good plant growth. The chlorophyll content highly correlates with the nitrogen content of the plant, which can be observed with the help of the red-edge band of RapidEye imagery. If the detectable relative content can be scaled by means of ground-based nitrogen measurements, an absolute value can be calculated, visualized as map layer, and later used for precision fertilizer application. The knowledge of plant status at different moments in the growing cycle and their comparison to standard values gives an indication about expected yields.
Of course, the results in the earlier stages of a growing season are less reliable than those acquired a few weeks prior to harvest. The accuracy of yield estimations further depends on the knowledge of other factors, such as meteorologic conditions, solar radiation, and so on. The RapidEye spatial resolution allows such investigations at field level. With the help of field size values, determined during creation of agriculture base information collection, real yield estimation values can be calculated.
An accurate estimation of yield will help to plan harvest, warehouse and food processors logistics as well as predicting the food supply and/or overhead, thats ready to export. In greater scale, this is an indicator for food prices in the world market.
For Forestry...
Forestry is the another huge vegetation class. Frequent image acquisition for monitoring purposes doesnt actually make a great deal of sense for forests because of their low growing activity. Nevertheless, customers ask us for annual status images of their forests. Such imagery is needed, especially if damage appears, such as after a storm event. The content of an image, acquired after such an occurrence, will be compared to the previous status image to determine the area affected and wood volume loss.
For boreal forests, RapidEye can determine the stem volume of coniferous trees with 70 to 80 percent accuracy. This technology is of interest for damage assessments and for plantation evaluation, wood supply management for paper mills and so on.
Insect infestations detection is another area of focus imagery that is of great value, as it gives an indication of trees vitality. Infestation centers, distribution directions, and speed, can be assessed. This is valuable information for responsible and cost effective pesticide application.
For Monitoring + Change Detection Services...
Changes result from different causes. If changes are related to spatial movements, the objects of interest need to be identified with high confidence in the data. The difference of coordinates describes the dynamics of location changes within a certain time period.
Changes in objects features, expressed in different spectral values, require a normalization of auxiliary conditions. Only in this case, the relevant changes can be detected. Due to the inhomogeneity of objects, a prior classification and masking will be necessary. This step results in change detection for whole classes of image content.
Appearing or disappearing objects can be detected, as well. This requires an initial detection of objects. Then, a comparison between identified objects can be completed. As a result, positive changes, or the appearance of new objects, and negative changes, and disappearing objects can be visualized at a map layer.
The RapidEye images pixel size allows detection of changes in objects greater 20x20m, or of linear objects wider than 10m. Infrastructural changes are often smaller. RapidEye imagery can be helpful in detecting areas of change, even if such is not possible to visualize exactly what has changed. This can be further investigated by ground teams, or with the help of other information sources.
A decreasing vitality of arable crops indicates plant stress, possibly caused by low soil moisture level. This is a first indicator for identifying progressive desertification activity. Abrupt changes, especially with sharp borders, speaks to accidental changes, such as land slides.
Constellation Competence
The information content, represented by 5 spectral bands, each with 12 bit radiometric resolution, is tremendous. With its high standard processing level Rapid Eye imagery is a preferable data source to be used in GIS, especially for agriculture, forestry, environmental and monitoring applications, as well as for topographic mapping and other spatial applications.