Cartographic quality contouring in PHOTOMOD 5.0 A. Sechin Scientific Director X th International Scientific and Technical Conference From Imagery to Map: Digital Photogrammetric Technologies September 2010, Gaeta, Italy

PHOTOMOD 5.0 today. Main changes for the last year automatic DTM creation algorithm improvements new powerful DTM filters (“removing” buildings and vegetation) speeding up automatic AT process (about 2 times) high-quality smooth contour lines more distributed processing (adding images, orthomosaicking, DTM, AAT ) VisionMap A3 sensor support  asynchronous sensors comfortable stereoprocessing (WorldView)  UltraCam metadata (interior and exterior orientation parameters) support  ADS 40 source data automatic pre-processing  self-calibration procedure improvements  more start approaches for bundle adjustment  precise block layouts by using DTM  speeding up raster visualization  saving block layouts to georeferenced rasters  RapidEye sensor support  satellite images in NITF + RPC format support  EXIF metadata support for non-professional cameras  and more…

The task We have: 1) A set of 3D-points, 2) A set of 3D-breaklines. 3) Region boundary.

The task We have: 1) A set of 3D-points. 2) A set of 3D-breaklines. 3) Region boundary. We need: 1) A smooth surface. 2) Contour lines with a given interval. We know: 1) Accuracy of 3D-points. 2) Required accuracy of contour lines (~1/3 of an interval).

Known methods of surface interpolation and approximation The picture is from a paper by Gabriela Droj «IMPROVING THE ACCURACY OF DIGITAL TERRAIN MODELS» Informatica, PHOTOMOD 4.X Delaunay Triangulation + Contour smoothing or Building DEM + Smoothing DEM + Contour smoothing

Delaunay triangulation disadvantages «Non cartographic quality» Manual smoothing parameters settings Contours can cross

Thin plate theory + boundary conditions (2) (1) (3)

Thin plate theory 1. Multi-grid iterative method 2. Polyline contours using grid surface 3. Smoothing and thinning of contours with the given accuracy (polylines or Bezier curves) CPU time ~ 20 minutes for 3 millions of input points

Example 1 “plain” (TIN – no Smoothing)

Example 1 “plain” (TIN + Contour Smoothing)

Example 1 “plain” (New Algorithm)

Example 2 “hilly” (TIN – no Smoothing)

Example 2 “hilly” (TIN + Contour Smoothing)

Example 2 “hilly” (New Algorithm)

Example 3 “mountains” (TIN – no Smoothing)

Example 3 “mountains” (TIN + Contour Smoothing)

Example 3 “mountains” (New Algorithm)

Dense DTM + contours Major and minor contours inPHOTOMOD 5.1 Major and minor contours in PHOTOMOD 5.1

Soap film PHOTOMOD 5.1 A similar approach is used in another task: We have a set of contour lines (from map digitizing). We need a DEM. In this case we use Soap Film equations (elliptical equations of the 2 nd order)

Thank you for attention !