On coastal areas, recent increase in production of open-access high-quality data over large areas reflects high interests in modeling and geovisualization, especially for applications of sea level rise prediction, ship traffic security and ecological protection. Research interests are due to tricky challenges from the intrinsic nature of the coastal area, which is composed of complex geographical objects of which spatial extents vary in time, especially in the intertidal zone (tides, sands, etc.). Another interest is the complex modeling of this area based on imprecise cartographic objects (coastline, highest/lowest water level, etc.). The challenge of visualizing such specific area comes thus from 3D+t information, i.e. spatio-temporal data, and their visual integration. In this paper, we present a methodology for geovisualization issues over coastal areas. The first challenge consists in integrating multi-source heterogeneous data, i.e. raster and vector, terrestrial and hydrographic data often coming from various ‘paradigms’, while providing a homogeneous geovisualization of the coastal area and in particular the phenomenon of the water depth. The second challenge consists in finding various possibilities to geovisualize this dynamic geographical phenomenon in controlling the level of photorealism in hybrid visualizations. Our approach is based on the use of a high-resolution Digital Terrain Model (DTM) coming from high resolution LiDAR data point cloud, tidal and topographic data. We present and discuss homogeneous hybrid visualizations, based on LiDAR and map, and on, LiDAR and orthoimagery, in order to enhance the realism while considering the water depth.

1. Antoine Masse, Sidonie Christophe
IGN, COGIT Laboratory
France
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015

2. GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015 2
• Coastal area
Between highest astronomical tide (shoreline)
and lowest astronomical tide (drying line)
• Spatio-temporal objects & phenomena
• Uncertainty: in motion (tides, sands)
• Incompleteness of data: underwater observation problems
• Imprecision: different definitions of an object at different scale
Sea/Land interface
ShorelineDrying line
Point Reyes, California
Red : DTM data (res. 1m, prec. 0,2m)
Yellow : 1:15,000 topomap
Blue : 1:50,000 topomap
Motivation: coastal area geovisualization
Different Shoreline definition

3. 3
Different uses & users  Different geovis
Limitations:
 Visual discontinuities and heterogeneity
between sea & land
 Perception of tides and/or water depth
for non-specialist users
C-Map®, navigation software
ScanLittoral®, Touristic/Public map
Interactive elevation simulation of lake Erie, USA (NOAA)
Ortho-image of La Grande Motte, Google Maps®
Ocean seafloor map of Hawai'i
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015
Motivation: coastal area
geovisualization

4. Purpose of the talk
4
• To convey sea dynamic information to users
Example of tide dynamic for informational purposes
• Hypothesis:
– Using heterogeneous data (maps, ortho-imagery,
LiDAR)…
– … to make homogeneous visualizations between
sea & land
– … by controlling photo-realism/abstraction
– … to convey tides & water depth perception
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015

5. Implementation
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015 5
Lidar acquisition (land/sea)
SHOM
0
5
10
Water elevation (in meters)
Tidal data, REFMAR® project
DTM (land/sea)
SHOM
Resolution: 1m/5m (land/sea)
Vertical precision: 0.2m/0.5m (land/sea)
Style
Rendering Engine Final
Rendering
Perception
Geographic
feature
External
data
Visual
Variables
Inspiration sources Colors, …
Maps, ortho-imagery, …
Abstraction, ortho-image-realism

6. Proposition of
geovisualizations
6
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015
4 examples for water depth visualization, static
and dynamic
Same data, different stylization of water depth:
- Abstraction maps
- (Ortho) photo-realism
0
5
10
Water elevation (in meters)
Data
Inspiration

7. 7
Inspiration: Map abstraction (1:25,000)
Location: Lanildut, Finistère, France
Data: DTM: Litto3D OpenData
Tidal data: REFMAR OpenData
Cartographic database
Color map
1st example: perception of
water depth by intervals
Low tide
05/28/2009
14:00
Depth (m) 0 -5 -10 -20
Color
Uses:
Tourism, Hiking, Fishing
Issues:
≠ producers
≠ uses
no tidal information
(ex: accessibility of Ile de Melon)
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015
High tide
05/28/2009
19:00

8. 8
1st example: perception of water depth intervals
Time x4000
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015

9. 9
Inspiration: Map abstraction
2nd example:
continuous
perception of water
depth
Location: Lanildut, Finistère, France
Data: DTM: Litto3D OpenData
Tidal data: REFMAR OpenData
Cartographic database
Colormap (interpolated)
Low tide
05/28/2009
14:00
High tide
05/28/2009
19:00
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015
Depth (m) 0 -5 -10 -20
Color

10. 10
2nd example: continuous perception of water depth
Time x4000
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015

11. 11
Inspiration: Ortho-image photo-realism
Location: Lanildut, Finistère, France
Data: DTM: Litto3D OpenData
Tidal data: REFMAR OpenData
IGN BD Ortho (land part)
Colormap (interpolated)
3rd example: continuous water depth perception
Depth (m) 0 -5 -10 -20
Color
Uses:
Exploration, landscape survey, …
Issues:
Color gaps
Depth gaps
no tidal information
visualization of a specific tidal stage
Low tide
05/28/2009
14:00
High tide
05/28/2009
19:00
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015

12. 12
3rd example: water depth perception
Brightness +20%
Contrast +40%
Time x4000
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015

13. 13
Location: Vannes, Morbihan, France
Data: DTM: Litto3D® OpenData
Tidal data: REFMAR® OpenData
IGN BD Ortho® (land part)
Colormap (interpolated)
4th example: water depth perception
Depth (m) 0 -5 -10 -20
Color
Uses:
Exploration, landscape survey, …
Issues:
Sands
Sea infiltration at high tide High tide
03/21/2015
16:30
Low tide
03/21/2015
10:20
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015
Inspiration: Ortho-image photorealism

14. 14
4th example: water depth perception
Brightness +20%
Contrast +40%
Time x4000
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015

15. Conclusion
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015 15
Goal: Convey sea dynamic information to geovisualization users
Thoughts for coastal geovisualization:
• Important: Data precision and land/sea visual continuity
 improve water depth perception
• Static and dynamic visualization -> different use, complementary
• Abstraction/Photo-realism: same data, different stylization

16. 16
- User Evaluation: uses and users?
• readability, handling, adaptation to specific use,
integration in final-user applications, etc.
• Task examples: How deep it is? When is it accessible?
- Tool adaptability
• Other data for validation
• Realism improvements
• With new data (ex: seafloor cover)
• With new stylization tools (expressive textures like
waves and sea stream, shaded relief)
Perspectives
Our method with other data
Carmel-by-the-sea, CA, USA
NOAA for DTM (sea) / Google Maps (land)
Shaded relief (Yu, 2005)
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015Water texture

17. Thanks
17
mapstyle.ign.fr antoinemasse.froxygene-project.sourceforge.net/
nice software nice project nice speaker
GeoVIS 2015 - ISPRS Geospatial Week - 10/01/2015