Comparison of Digital Elevation Models Produced with Photogrammetric Usage of UAV by Geodetic Techniques

Abstract

Unmanned Aerial Vehicles (UAV) use in the production of the map for photogrammetric purposes. Unlike aerial photogrammetry, UAV cameras are non-metric amateur cameras. Therefore, they need some operations to use in photogrammetry. Structure from Motion (SfM) algorithms prefers for processing images because of the usage of the non-metric cameras. These algorithms generally identify key-points (via feature extraction) on the photos and match tie-points (via feature point matching) in overlap images. SfM is a photogrammetric technique that produces keypoint to match by identifying key points, such as edge-to-corner points, through high-resolution RGB photos. The scope of this study was to compare the results obtained by UAVs and the results acquired by ground truth data. In this comparison, SfM algorithm performance, the effects of flight height, overlap rate, and UAV-type on the model investigated, and significant results achieved. Additionally, the models obtained from the UAV photographs with different flight heights and overlaps in the areas with varying characteristics of the slope compared. Consequently, it determined the difference between around 20 cm (Z value), comparing the flight height of 80 m and the flight height of 120 m. Since it is observed that the flight height does not have a significant effect.  

Keywords

• DEM
• SfM
• UAV
• Accuracy Assesment

Jeodezik Tekniklerle ve İHA'nın Fotogrametrik Kullanımı ile Üretilen Sayısal Yükseklik Modellerinin Karşılaştırılması

Öz

Son yıllarda fotogrametrik amaçlı harita üretiminde İnsansız Hava Araçları (İHA) sıklıkla kullanılmaktadır. Hava fotogrametrisinde kullanılan kameraların aksine, İHA kameraları metrik olmayan kameralardır. Bu nedenle fotogrametride kullanmak için bazı işlemlere ihtiyaç duyarlar. 3 Boyutlu model üretiminde kameranın farklı pozisyonlardan bindirmeli fotoğraf çekimi esasına dayalı Structure from Motion (SfM) algoritmaları, metrik olmayan kameraların kullanılmasına olanak sağlamaktadır. Bu algoritmalar genellikle fotoğraflardaki anahtar noktaları (öznitelik çıkarma yoluyla) tanımlar ve bindirmeli görüntülerde bağlantı noktalarını (öznitelik noktası eşleştirmesi yoluyla) eşleştirir. SfM, yüksek çözünürlüklü fotoğraflar aracılığıyla kenar noktaları köşe noktaları gibi kilit noktaları (keypoint) tanımlayarak eşleşecek anahtar nokta (tie point) üreten bir fotogrametrik tekniktir. Bu çalışmanın amacı, İHA'lar ile çekilmiş fotoğraflardan 3B model üreterek, arazi verilerinden elde edilen 3B modelin karşılaştırılmasıdır. Bu karşılaştırmada SfM algoritma performansı, uçuş yüksekliği, bindirme oranı ve İHA türünün model üzerindeki etkileri incelenmiş ve önemli sonuçlar elde edilmiştir. Ayrıca farklı uçuş yüksekliklerine sahip İHA fotoğraflarından elde edilen modeller ve farklı eğim özelliklerine sahip arazilerde de karşılaştırmalar gerçekleştirildi. Sonuç olarak 80 m uçuş yüksekliği ile 120 m uçuş yüksekliği arasındaki farkın (en büyük fark olarak) 20 cm olduğu (Z değerinde) tespit edilmiştir.

Anahtar Kelimeler

• Doğruluk Analizi
• İHA
• SfM
• SYM

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