REFERENCE SURFACE

LTJG Anthony Klemm and Prof. Shachak Pe’eri

LAB 3

Overview

Lab work

• Lab 1: SETTING UP THE WORKSPACE (ARCMAP)

• Lab 2: LOADING THE DATASETS INTO THE PROJECT

• Lab 3: REFERENCE SURFACE

• Lab 4: BATHYMETRIC DIFFERENCE LAYER

• Lab 5: VESSEL TRAFFIC LAYER

• Lab 6: HYDROGRAPHIC CHARACTERISTICS LAYER

• Lab 7: CHART ADEQUACY

DTM models - scales

The boundaries separating different spatial and temporal scales are not very clear and they may vary with individual processes and/or landscapes

/bathy

J.P. Wilson and J. C. Gallant, 2000. Terrain Analysis: Principles and Applications Wiley, pp. 479.

Topo/bathy scales

Tasks associated with DEM

5

Sources for generating a surface

• Single specific point elevation data: Lead line measurements

Field surveying (GPS, laser scanner)

• Contour data: Digitization of existing charts and topographic maps.

• Remote sensed data: Sonar (single beam, MBES, and interferometry)

Photogrammetry (stereoscopic interpretation)

Lidar (topographic lidar, airborne lidar bathyetry)

Radar remote sensing (InSAR)

Data structures

• Conventional grids

• Triangulated irregular networks (TIN)

• Contours

Grid TIN Contour

Childs, C., 2004, Interpolating surfaces in ArcGIS Spatial Analyst, ArcUser July-September.

DEM interpolation methods

• Triangulation (TIN)

• Local surface patches

• Local adaptive gridding

TIN example

Childs, C., 2004, Interpolating surfaces in ArcGIS Spatial Analyst, ArcUser July-September.

DEM interpolation methods

Raster and Vector

• Representation (point cloud versus an array)

• Benefits (representation, size and processing time)

• Limitations (representation, size and processing time)

Raster versus vector (In ArcMap)

Raster Vector

Chart soundings versus a smooth sheet

Chart soundings are a subset of the smooth sheet (or fair sheet) soundings cartographically chosen to represent depths of the sea floor between contours to support safe surface navigation.

Reference Surface (Charted Depth)

The water depth also contributed to the adequacy level of the chart. For example, bathymetric change between two surveys in within a depth range of 5 to 10 m is more critical that changes at a depth changes that occur with 50 to 60 m.

Accordingly, classified results will be normalized with depth.

Unless recent hydrographic surveys are available and not incorporated into the chart, the reference depth will be derived based on the smooth sheet or chat soundings and contours (if smooth sheet is not available).