aerial photography on Duvansko Polje (Hercegovina) II. Terrain modeling.

October 25th, 2014 § 0

Previous post about an aerial imagery in south Bosnia and Herzegovina was focused primarily on spectacular beauty of karstic landscape (Fig. 01) and the presentation of general results as well.

However I realised that there are no satisfying Digital Elevation (DEM) Model dataset for a further GIS analysis; state-owned spatial data resources are completely missing or quite poor. After some inevitable investigation I asked myself if there is an option to gain DEM by my own. The problem is that I have only skew (side-shot) imagery and a few terrestrial coordinates so the only posible way would be the space resection method for generating basic geometry. On the other side:

  • I have tons of skew photos for disposal covering the whole area (Fig. 02)
  • space resection method and its implementation via Church method (Analytical methods in aerial photogrammetry, 1932); pyramidal method; or Direct Linear Transformation is very well described and applicable
  • and finally, have You ever noticed space resection photogrammetry plugin in MATLAB (Fig. 03)?
  • I used collinear equation with direct linear transformation for distinct sets of corresponding photos and generated individual TINs (Fig. 04). After beeing welding them I have got one major TIN for the whole area (Fig. 05) and exporting it into AutoCAD Civil environment I got a basic geometry for further dirty tricks… (Fig. 06).

    … based on simple styling, contours generation and raster mapping (Figs. 07 – 09).

    Obviously there is quite straightforward possibility for quick generation of terrain
    shapes from single and skills undemanding photo set. The method is software independent and process presented in this report is only one way how to seize the solution of this problem.

    The process itself and respective results are not unique and not groundbreaking by no means. Geometry generating via the space resection photogrammetry is widely used in production environment and even popular applications. Widespread Google Earth application is one of many.

    Although an intended goal was achieved there is no control mechanism concerning the model precision and its spatial reliability – both in absolute and relative meaning. The precision could be verified by additional geodetic surveying but such a scenario increases the time and budget demands.

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