1 Background - mountain.PROJECTS

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TURKU UNIVERSITY DEPARTMENT OF GEOGRAPHY PUBLICATIONS B Nr 4SynthesisConsidering the user requirements (Table 2), remote sensing techniques were assessed andexperimented for their applicability for long-term operational monitoring system for Europeanglacial areas in case of two glaciers. In framework of OMEGA, it is difficult to define "thebest and the unitary" operational remote sensing technique for the purpose. Nevertheless,airborne laser scanning, aerial photography and high resolution optical satellite imagery coverin this moment best the glaciologists needs. It has also become clear that in case of long-termmonitoring it is of utmost importance that all data have a common datum. In OMEGA,WGS84/UTM33 were used for the purpose. It is also necessary, that local co-ordinate systemsbe properly controlled when referring to the global system. In OMEGA, creating local GPSpoint networks, which were further connected to local control points, performed this.As far as it regards both technical and economical aspects, spaceborne optical remote sensingtechniques - especially very high-resolution imagery – can be considered to be the primarysource in global scale. They are suitable for continuous change detection in periodic inventoryfor both glacial area and volume observation. A system that produces very high resolutionimages with good geometrical quality, and has a well organised satellite operation, systemmaintenance and image reselling network, can serve operational glacier monitoringapplication and yield feasible products.Optical satellite images respond well for most of the user requirements, which were set for theOMEGA project. From an Enhanced Thematic Mapper (ETM+) image, surface reflectancescan be computed after performing radiometric, atmospheric and topographic corrections. Inaddition, ground-based spectral measurements provide supportive data at point specificlocations. The geometric accuracy of IKONOS images fulfills requirements set by glacierscientists. This can be achieved by using only few ground control points, which is a veryimportant advantage in areas where no ground control exists and where it would be very hardto establish lots of accurate ground control points. Also the image acquisition process ofIKONOS images proved to be very trustworthy. Therefore, IKONOS image data has highpotentiality to be utilized in glacier monitoring applications. The EROS A geometricalaccuracy does not fall within the range of requirements of glacier monitoring applications.As far as it regards aerial photogrammetry - including laser scanning and digital imaging – itbecomes superior in accuracy but can be considered cost efficient only in local scale. Thesetechnologies can be timely controlled and are therefore suitable for continuous monitoring ofglaciers with respect to changes in the glacial annual period. Aerial photography is acceptablefor producing a DEM for glacier monitoring, expecting that the ground control is organisedaccording to normal mapping practices. Today this includes the GPS observations during theflight and a sparse network of GCP's built before the flight. The ground resolution is accurateaccording to the image scale. However, these technologies are cost efficient only if theglaciers are relatively small and they locate near operative airports. In OMEGA, laserscanning was the only technology, which could be operated according to the preset schedulein the Austrian test areas. Airborne laser scanning has a main advantage towards aerialphotography in the firn areas of a glacier.Terrestrial remote sensing can be considered for local validation of monitoring data and forlocal research purposes. Sort-term kinematic applications would be on of the furtherapplications but were not yet covered in OMEGA.42
PETRI PELLIKKA AND KARI KAJUUTTI (ED)Table 2. Table of requirements and the key availability of remote sensing technologies.Requirements /Variables,unitsGlacierinventoryGlaciertopography(extent andelevation), mor kmGlacier/snowsurface state, 6classesSnow coverarea, km²Glacier massbalance, kg/yrGlacier surfacebalance,kg/(m²×yr)Glaciervelocity, m/yror cm/dayChange in icethickness, m/yrChange inglaciated area,km²/yrChange inglacier length,m/yrChange inglaciervelocity, m/yr²CycleHorizontalresolutionVerticalresolutionTimeresolutionAccuracyAvailableremotesensingtechnology30 years 10 m 0.5 m 2 years TBD All5 years 10 –20 m 1 m, contourinterval: 20 –40 m1 year horizontal:5-10 mvertical: 0.5mAerialphotography,or VHRsatelliteimagery inlarge andremote areas1 day 1 – 2 km 100 – 250 m 3 – 6 months ± 5 % VHR satelliteimagery1 day 0.1 km N/a 3 months ± 5 % VHR satelliteimagery1 year 5 km 0.1 - 1 m 0.5 – 1 year ± 100 kg/yr VHR satelliteimagery1 year 1 – 10 km² 1 m 1 year ± 1kg/(m²×yr)10 years,seasonal0.5 – 1 km N/a 3 – 6 months ± 5 m/yr or ±1 cm/day5 years 2 – 5 km N/a 1 year ± 0.01 – 0.1m5 – 7 n/a N/a 1 year ± 0.5 - 1% VHR satelliteyearsimagery5 years 10 m N/a 1 year ± 2 m/yr VHR satelliteimagery10 years 1 km N/a 1 year ± 1% (1m/yr²(Interferometric SAR)Spaceborne interferometric SAR technology showed its develobility for short-term kinematicapplications, whereas airborne interferometric SAR remained as rare and unproventechnology, but still owing high potentially in volumetric monitoring. In this context, satelliteradar interferometry is not a concurrent with an airborne stereophotogrammetry in DEMgeneration, but it has serious advantages in (all-weather) detection and measurement of shorttermwinter glacier changes, motions and deformations with an accuracy of ca. 2 cm/day.There are no reasonable alternatives among other techniques, which are far less sensitive andaccurate in doing that. Albeit very sensitive, the INSAR method is cheep, since onespaceborne SAR scene (we need two - for single model, or four - for differential model)covering the area of 10 000 km² costs at max. 800 €. The DINSAR processing takes about 4 -6 hours of working time (ca. 1200 €) per differential model. This means that one km² of theready spaceborne differential model showing changes in the cm-range over the area of 8.000to 9.000 km² (overlap) costs about 0.4 - 0.5 €.43
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