Maria von Schoenermark

Acquisition of High Quality Remote Sensing Data Using a UAV Controlled by an Open Source Autopilot

This paper describes the integration and application of the Paparazzi autopilot into an aircraft system for scientific research on remote sensing. The main purpose of the presented UAV, Stuttgarter Adler , is remote sensing of the environment for fundamental radiometric research as well as applications in agriculture, surveying and mapping. Employing a UAV for the retrieval of remote sensing data of quality comparable to data from manned missions represents a very flexible and inexpensive method of data acquisition. The sensors required for the intended resolution total several kilograms in weight and led to the construction of a matching airplane. All intended missions require a robust and precise control of the aircraft during image acquisition flights, which can only be achieved with an automated pilot assistance system. The Paparazzi system was chosen because its open source approach allowed to adapt the autopilot to the specific mission requirements. Interfaces to the digital remote control and to the camera and spectrometer payloads have been created. Test flights show good results in stabilizing the airplane and controlling the payload.Copyright

Reflection properties of vegetation and soil with a new BRDF database

At least in the visible and near infrared spectral region the basic principles about the bi-directional reflectance distribution function (BRDF) have achieved an advanced state. This basic knowledge has been summarized by international well known scientists and firstly published in a book. A CD-ROM data base is attached to the book. For this paper these data have been used for a very first statistical synopsis. The measurement results of different scientists for similar targets and similar geometric conditions differ partly to a great extent. Hence mean values and variances cannot presently be used to describe the BRDF of different surfaces. The anisotropy factor defined by Sandmeier seems appropriate to be used in some investigations. The data sets are not sufficient for serious statistical analyses. Further measurements are essential to overcome the gap from examples to confidential statistical evaluations. In the last section the measurement methods planned by the University of Stuttgart for a ground measuring device and by target pointing of a small satellite are discussed.

Real-Time Evaluation of Remote Sensing Data on Board of Satellites

The application of FPGAs for remote sensing on board satellites is discussed and first results are demonstrated

Advances in BRDF field measurement: New principle and instrument

The advances in the capabilities of sensors and methods used for remote sensing the earth call for taking into account angular effects. The effect is described through the “bidirectional reflectance distribution function” (BRDF). For most applications BRDF models are used. To validate such models and for in-flight calibration purposes the measurement of BRDF of natural surfaces is necessary. Most of the methods used to measure angular reflection properties in the past had to use interpolation or smoothing algorithms in the data processing [1, 2]. These computations influence the resulting BRDF. We present the instrument GRADIS (Ground Reflectance Angular Distribution Investigation System) which avoids this problem by using a new principle for acquiring the data. Several measurement campaigns were conducted for basic measurements of different surfaces and for calibration measurements of airborne instruments.

New airborne digital camera with multispectral and stereo capability

Joint development work by DLR and LH Systems has produced a new camera concept called Airborne Digital Sensor which is using forward-, nadir- and backward-looking linear arrays on the focal plane. The camera system provides panchromatic and stereo information using three CCD lines and up to five more lines for multispectral imagery including two NIR channels. Each CCD array for panchromatic measurements has 24000 elements, resulting in a field of view of 64 degrees (across track FOV) by using a focal length of 62.5 mm. The sensitivity covers a dynamic range of 12 bit with a recording interval time of 1.2 ms per line. The performance of the camera allows a 3D and multispectral image with a ground sample distance of 25 cm for an area of 300 square miles within a flight time shorter than one hour.