IZDELAVA DIGITALNEGA MODELA POVRŠJA IN ORTOPODOB IZ STEREO POSNETKOV IKONOS, ZAJETIH V ISTEM PRELETU

Aleš Marsetič, Krištof Oštir

DOI: 10.15292/geodetski-vestnik.2010.03.417-432

 

DIGITAL SURFACE MODEL AND ORTHO-IMAGES GENERATION FROM IKONOS IN-TRACK STEREO IMAGES

Aleš Marsetič, Krištof Oštir

DOI: 10.15292/geodetski-vestnik.2010.03.433-449

 

Izvleček:

V članku je opisana izdelava digitalnega model površja (DMP) in ortopodob iz pankromatskega in multispektralnega stereopara posnetkov Ikonos. Pri tem se ugotavlja primernost posnetkov za kartiranje višine vegetacije večjega območja in uporabnost rezultatov za namene različnih prostorskih analiz. Koraki obdelave so vključevali izravnavo posnetkov s snopi z različnimi razporeditvami in številom oslonilnih točk, izdelavo digitalnega modela površja in ortopodob ter vrednotenje rezultatov. DMP je bil zaradi boljše ločljivosti posnetkov izdelan samo iz pankromatskega stereopara. Rezultati so bili vrednoteni s primerjavo z zelo natančnim modelom površja, izdelanim iz lidarskih podatkov. Analize so pokazale, da je povprečna višinska razlika med modeloma 8,2 metra, pri čemer je samo tretjina razlik manjših od 3 metrov. Rezultati so bili slabši na strmih pobočjih z visoko vegetacijo in območjih s sencami, ki so jih povzročili hribi in oblaki. Po drugi strani so bili rezultati vrednotenja ortopodob z ortofoto posnetki veliko boljši, saj so RMSE (koren povprečne kvadratne napake) položaja znašali pod 1,5 piksla za oba uporabljena stereopara.

Ključne besede: zračno lasersko skeniranje, lidar, topografija, gostota lidarskih točk, teorem vzorčenja

 

Abstract:

The paper describes the generation of a digital surface model (DSM) and orthoimages from panchromatic and multispectral Ikonos stereopairs. It assesses the suitability of the images for vegetation height mapping of a large area and the applicability of the results for various spatial analyses. The processing steps involved stereo bundle adjustment with various sets of ground control points, digital surface model extraction, orthoimage generation and evaluation of the results. Although both multispectral and panchromatic stereoimages were processed, the DSM was generated only for the panchromatic stereopair due to its higher resolution. For evaluation purposes it was compared to very accurate lidar elevation data. The analysis revealed an overall vertical difference between the models of 8.2 m, where only one third of the differences are below 3 m. The results were worse in steep areas with high vegetation and regions with shadows caused by hills or clouds. Better results can be obtained with previous manual or automatic editing of the automatically extracted model. On the other side, orthoimages that were also produced are very accurate – the evaluation showed results with horizontal RMSE errors below 1.5 pixels for both stereopairs when compared to aerial orthophotos.

Keywords: Ikonos stereo satellite images, digital surface model, stereoscopy, ortho-images, evaluation

 

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