# Presentation: 657665

## A Roadmap for a Seamless Elevation Surface: Benefits to Storm Surge Forecasting

**Lindy Dingerson**
**NOAA Coastal Services Center**

## Importance of Topobathy DEMs

- High-resolution elevation data contributes to making more accurate storm surge forecasts

**Notes:**
Many applications of topography datasets (water flow over land)
Many applications of bathymetry datasets (navigation)
Many applications of combined topography/bathymetry datasets (storm surge modeling)
surge models running on more accurate DEM grids
 increased accuracy of inundation extent

Stress importance of why you might use a topobathy – continuous surface needed for looking at things that happen at or across the land/water interface.
Will be talking about some things the Center does to increase access to these kinds of datasets and the knowledge of how to manipulate them

## A Roadmap to a Seamless Elevation Surface

- Seeks to answer the questions:
- 	What is the “best available” topography and bathymetry data and where can I find it?
- 	What are the techniques available to create a uniform reference and integrate data?
- 	What can I do with a seamless topobathy model based on high-resolution data sets?

**Notes:**
CSC is bringing together information necessary to access and work with these datasets (and better address the challenges of topobathy integration)
Roadmap is designed to provide information on where data resources exist, where there are gaps in the data, what tools and techniques are available for manipulating datasets, potential applications of DEMs, and data standards necessary for each application.

## A Roadmap to a Seamless Elevation Surface

- Seeks to answer the questions:
- 	**What is the “best available” topography and bathymetry data and where can I find it?**
- 	What are the techniques available to create a uniform reference and integrate data?
- 	What can I do with a seamless topobathy model based on high-resolution data sets?

**Notes:**
CSC is bringing together information necessary to access and work with these datasets (and better address the challenges of topobathy integration)
Roadmap is designed to provide information on where data resources exist, where there are gaps in the data, what tools and techniques are available for manipulating datasets, potential applications of DEMs, and data standards necessary for each application.

## Data Inventory: Gulf of Mexico

- On-line inventory of publically-available topography and bathymetry data sets in the Gulf of Mexico (time stamp as of November 15, 2007)
- Focused on high-resolution elevation data sets
- Two sets of maps
**Data Gap Analysis by Location**
**Data Gap Analysis by Collection Date**
- Accompanied by supporting information including descriptions of collections, where to access data, and topographic lidar attributes (datums, accuracies, etc.)

**Notes:**
Focuses on high-resolution datasets
Close-to-final draft complete, final revisions occurring now
Final Inventory available March/April 2007
Available as a mapbook of pdf files and will eventually be available as a geodatabase

**Notes:**
CSC is bringing together information necessary to access and work with these datasets (and better address the challenges of topobathy integration)
Roadmap is designed to provide information on where data resources exist, where there are gaps in the data, what tools and techniques are available for manipulating datasets, potential applications of DEMs, and data standards necessary for each application.

## Slide 7

**Notes:**
Point out major features
Color of county indicated what type of elevation data exists and what stage it’s in
Shaded are indicates that there is a proposed collection for this area
Black stuff is NOS hydrography lines showing exactly where bathymetry exists
Red is shoreline surveys of topobathy lidar

## Inventory Supporting Information

## A Roadmap to a Seamless Elevation Surface

- Seeks to answer the questions:
- 	What is the “best available” topography and bathymetry data and where can I find it?
- 	**What are the techniques available to create a uniform reference and integrate data?**
- 	What can I do with a seamless topobathy model based on high-resolution data sets?

**Notes:**
CSC is bringing together information necessary to access and work with these datasets (and better address the challenges of topobathy integration)
Roadmap is designed to provide information on where data resources exist, where there are gaps in the data, what tools and techniques are available for manipulating datasets, potential applications of DEMs, and data standards necessary for each application.

## Why Do We Care about Reference?

-    Creating a common reference for all data sets allows you to minimize error in the final DEM.

- Santa Rosa, FL; courtesy of CSDL

-    **The Issue:**
-    Topo and bathy referenced to different datums

**Notes:**
One of the major challenges with using an integrated topo/bathy surface is creating a common reference
Topo is referenced to static references that are gravitational or mathematical
Bathy is referenced to local tidal datums
Different datums suit different applications, but there needs to be a way to combine the two datasets
Creating a common reference allows you to minimize error in final DEM
Picture: is a DEM in development, and the image is of multiple datasets referenced to a common surface...you can see where datasets are joined together and adjustments will need to be made.  Common reference gives you the first step toward an accurate high-resolution DEM

## Datum Conversion Techniques

- Issue:**  **Accurately converting between tidal and orthometric/ellipsoidal datums
**VDatum**** –** estimates tidal datums using a complex hydrodynamic model and tidal benchmark data
**Harmonic Constant Datum Method**** –** estimates tidal datums using major tidal influences (sun, moon, rotation of earth) and tidal benchmark data
**Linear Interpolation**** –** estimates tidal datums using tidal observations at benchmarks and interpolating between tide stations
**No Conversion**** –** no relationship between datums is established. Therefore, datums are assumed to be equal.

**Notes:**
I mentioned the disconnect between topo and bathy reference
For high-resolution applications, it’s necessary for a common reference to be established
A variety of methods have been established to make this possible, each of which uses different inputs for a varying degree of cost and accuracy of the end product

## NOAA Technical Memorandum NOAA/CSC/20718-PUB

**Notes:**
These methods are explained in detail in this document which addresses reference, datum conversion and data integration
This is in draft form, but it will be available in Summer/Fall 07

## Data Integration

**Notes:**
Data integration piece refers to preferences/needs for a topobathy surface
What resolution/accuracy can the model handle efficiently?
Gridded or raw points?
Data standards the source data can support
Structured v. unstructured
All are valid, but some are better suited for certain applications

## A Roadmap to a Seamless Elevation Surface

- Seeks to answer the questions:
- 	What is the “best available” topography and bathymetry data and where can I find it?
- 	What are the techniques available to create a uniform reference and integrate data?
- 	**What can I do with a seamless topobathy model based on high-resolution data sets?**

**Notes:**
CSC is bringing together information necessary to access and work with these datasets (and better address the challenges of topobathy integration)
Roadmap is designed to provide information on where data resources exist, where there are gaps in the data, what tools and techniques are available for manipulating datasets, potential applications of DEMs, and data standards necessary for each application.

## DEM Applications

**Coming soon:** on-line reference addressing topobathy DEM applications and general data and DEM standards necessary for some coastal applications
- Addressing topobathy applications such as
**Coastal Flooding**
**Shoreline Delineation**
**Erosion Monitoring**
**Sea Level Rise**
**Habitat Mapping**

**Notes:**
Last piece of the Roadmap is the DEM applications piece
Looking at applications and the data standards necessary for each applications
Looking at high resolution apps, like shoreline delineation, to somewhat lower resolution apps, like inundation modeling

## For More Information

***www.csc.noaa.gov/topobathy***
- Lindy Dingerson
***Lynne.Dingerson@noaa.gov***