Cartographic quality Cartographic quality contouring in contouring in PHOTOMOD 5.0PHOTOMOD 5.0A. SechinA. Sechin

Scientific DirectorScientific Director

Xth International Scientific and Technical Conference From Imagery to Map: Digital Photogrammetric Technologies

September 2010, Gaeta, Italy

PHOTOMOD 5.0 today. PHOTOMOD 5.0 today. Main changes for the last yearMain 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 taskThe task

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

The taskThe task

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

We need:We need:1) A smooth surface.2) Contour lines with a given interval.

We know:We know:1) Accuracy of 3D-points.2) Required accuracy of contour lines (~1/3 of an interval).

Known methods of surface interpolation and Known methods of surface interpolation and approximationapproximation

The picture is from a paper by Gabriela Droj«IMPROVING THE ACCURACY OF DIGITAL TERRAINMODELS» Informatica, 2008.

PHOTOMOD 4.X Delaunay Triangulation + Contour smoothing

or

Building DEM +Smoothing DEM +Contour smoothing

Delaunay triangulation disadvantagesDelaunay triangulation disadvantages

«Non cartographic quality»

Manual smoothing parameters settings

Contours can cross

Thin plate theoryThin plate theory

+ boundary conditions

(2)

(1)

(3)

Thin plate theoryThin 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 minutesfor 3 millions of input points

Example 1 “plain” (TIN – no SmoothingExample 1 “plain” (TIN – no Smoothing))

Example 1 “plain” (TIN + Contour SmoothingExample 1 “plain” (TIN + Contour Smoothing))

Example 1 “plain” (New AlgorithmExample 1 “plain” (New Algorithm))

Example 2 “hilly” (TIN – no SmoothingExample 2 “hilly” (TIN – no Smoothing))

Example 2 “hilly” (TIN + Contour SmoothingExample 2 “hilly” (TIN + Contour Smoothing))

Example 2 “hilly” (New AlgorithmExample 2 “hilly” (New Algorithm))

Example 3 “mountains” (TIN – no SmoothingExample 3 “mountains” (TIN – no Smoothing))

Example 3 “mountains” (TIN + Contour Smoothing)Example 3 “mountains” (TIN + Contour Smoothing)

Example 3 “mountains” (New AlgorithmExample 3 “mountains” (New Algorithm))

Dense DTM + contoursDense DTM + contours

Major and minor contours inMajor and minor contours in PHOTOMOD 5.1PHOTOMOD 5.1

Soap filmSoap 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 2nd order)

Thank you for attentionThank you for attention ! !