October 13, 2003
Marine GIS--Where Multidimensionality Presents Special Challenges
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Susan Smith - Managing Editor

by Susan Smith - Managing Editor
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Meeting the Challenges

For some time, the sea floor has been represented successfully with echo sounding and other multibeam sounding equipment that can collect data across a swath of seafloor and then represent that as an interpolated surface. The topography which represents the seafloor can answer questions such as how high are 'Pinnacles,' that rise from the seafloor. Will these pinnacles, [or reef platforms or shipwrecks], pose a threat to large transportation or shipping vessels? is just one piece of important data necessary to shipping industries. (Seamounts are often too deep to affect commercial shipping lanes and are of interest more in terms of hosting important habitats or being important sources of
geothermal energy.)

An example is a USGS study out of San Francisco Bay that may indicate areas that need to be trimmed off the rock pinnacles because they pose a threat to incoming and outgoing vessels. (Source = USGS Open-File Report 01/9/2003)

Other forms of data useful to marine GIS include LIDAR collection of the shoreline. This high resolution data can reveal details such as ripples in the sand. Satellites that can now provide images of not only the sea surface [height] but also sea surface temperature and currents, upwellings and bottom type. Other data collection methods provide information on what's below the sea surface and also what's below the sea floor. Layers of sediments and different types of rocks, layers can be found and identified using sub bottom profilers and side scan sonars. They can be used to gather subsurface data that gives scientists an idea of what kind of bottom type it is - if it's sediment or oil,
can be of interest to those involved in oil drilling or seeking core samples. Much of that data can be remotely sensed using sound waves with LIDAR.

this LIDAR data in the 3D environment creates some new challenges,” said Breman. “In creating a data model structure we have approached it so in order to ingest this data you can actually have a place for not only the x and y but the z and the multiple z values, the time variables and any measures that may be important to include as well. If you think of it in letters there is x, y, z, t and m. t is for time and m is for measures which can be used for modeling.

3D visualization is very important in understanding such changes as sea level rise, one of the more significant potential results of climate change. People want to know what's going to happen with their coastlines in 50 or 75 years. If it is true--as many scientists believe -- that the sea level is going to rise in our lifetimes significantly, then planning needs to be done to prepare for this. “There are things we can do to assess whether or not there will be a need to build up or move back or create breakwalls, or propose solutions for a change of sea level,” attested Breman.

Breman concluded it is safe to speculate that sea level rise will be influenced by global climate change. “We're creating tools to be able to predict the amount of global climate change and sea level rise change more accurately. With advancements in data we're really poised to come up with some of those answers. And it's not something where I can say, 'here's the answer,' but the tools that we have available right now put us in a better position to answer some of these questions.”

These are questions that impact ourselves and our children within our lifetimes. What most people don't realize, noted Breman, is that sea level change is generally something that happens over thousands of years. But the rise in the past 100 years has been notably sharp. “It indicates sea level rise based on global climate change is due to not only the warming which breaks up the ice sheets which creates water where there used to be volumes of water locked up in the ice. Now that ice is melting and creating a greater volume of water accounting for (some say) half of the factor in sea level rise. The other 50 % is attributed to 'thermal expansion' of the water. Time will tell how much
climate change will affect our coasts with nearshore influences such as erosion, I just hope that we are ahead of the curve.”

In addition to the challenges presented by nature, Breman addressed the fact that over the past five years the sensors and availability of live streaming data gives us a different amount of data to work with so we're faced with a new larger volume of data--thousands of measurements (or Gigabytes of data) per hour, that create, over time, a huge challenge to work with in the computer environment. This presents new questions of how to work with that volume and type of data.

An important part of marine work is being able to measure the water column, defined as the body of water between benthic and surface. Because of its dynamic nature and because it's difficult to represent a true 3D environment, the water column has been difficult to measure. Breman is currently working on the representation display and the analytical tools which include animation tools and extrusion (the stretching of the water column) within this environment.

Current Process

According to Dawn Wright, the Marine Data Model is now in the beta test stage. “We finished a draft of the model with a lot of input from people in the community. We have an international review team of 25 marine/coastal GIS specialists and a core working group of myself and Pat Halpin of Duke University, Joe Breman and Michael Blongewicz of the Danish Hydraulic Institute, who was also instrumental in the development of ArcHydro. The four of us gave a technical workshop at the User Conference to introduce the community to the features of the model and encourage them to start using it, testing it, especially in case studies,” Wright explained. “We're at that stage where we
are very keen on
seeing the model implemented, and in publishing the results for our community of users, as well as for related communities such as our colleagues in atmospheric science and terrestrial geology.”

The current repository and geodatabase samples for the Marine Data Model are for ArcGIS 8.3. Joe Breman is doing his development work in ArcGIS 9. There are also some older geodatabases that haven't upgraded to 8.3 yet because of some backward incompatibility issues.

The field of marine GIS is growing and a whole new range of applications are being developed. Coastal resource managers, nautical archaeologists, marine technologists, the U.S. National Marine Sanctuary Program, and the Navy are just some of the users. According to Wright, some oceanographers have had difficulty fully adopting the technology because they really need to track parcels of water, and look at climate change issues in 3D and 4D. “There is an ArcGIS atmospheric data model initiative in the works as well,” claimed Wright. The ocean atmosphere interface is extremely important and they face some of the same challenges in working with GIS that we do. Instead of water
they're dealing with
air.” The merging of the many data model initiatives creates a mechanism to leverage progress, so we can “go deeper” in our understanding of the world we live in, and how it is changing.

Related Links:


Sanborn announced that the company signed an agreement with Boulder, Colorado-based Vexcel Corporation to acquire its new UltraCam-D large format aerial camera. The UltraCam-D has a base panchromatic resolution of 11,500 x 7,500 pixels, in addition to four color channels (red, green, blue and near-infrared). Imagery is collected at a depth of 12 bits per channel and a rate of more than one frame per second. Forward-motion compensation can support pixels as small as 3 cm on the ground.

Global Energy Decisions, LLC (Global Energy) announced it has acquired ENERmap -- a leading energy industry mapping and geographic data firm. ENERmap produces detailed print, electronic, and interactive maps for the electric, coal, and transportation industries. Terms of the deal were not disclosed.

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