# Presentation: 906916

## North Carolina Geodetic Survey

- National Height Modernization System in
-  North Carolina
- Lessons Learned

## Benefits to North Carolina

- Geodetic control network
- Global Positioning System (GPS) base station network
- North Carolina Floodplain Mapping Program
- North Carolina Land Records Management Program

## Operational & Proposed GPS Base Stations (CORS) 

- Total: 84 CORS; 43 existing (including installation in progress), 2 NDGPS

## Real Time Kinematic (RTK) Network

**Real Time Kinematic (RTK) Network**

## OPUS

**OPUS**

## North Carolina Floodplain Mapping Program

**North Carolina Floodplain Mapping Program**

## Components of a DFIRM Supported by NHMS

**DFIRM**

**=**

## NHMS Supports the Collection of Elevation Data

**“****First returns”** provide Digital Surface Models (DSMs)
- Roof tops
- Tree tops

**“****Last returns”** can provide Digital Elevation Models (DEMs) of the “bare earth”  if fully processed to remove buildings and vegetation that were not penetrated by    the LIDAR pulses

**LI**ght** D**etection** A**nd** R**anging (LIDAR)

## Hill Shade model

## LIDAR Digital Elevation Model

## QC Assessment Report Burke County, Catawba River Basin 

**Notes:**
This slide is shown for two reasons.
First, it shows that hot asphalt can also absorb LIDAR laser pulses, as indicated by the lack of LIDAR points on the road south of the bridge.
More importantly, this slide shows GPS point 106 surveyed near the southwest corner of the bridge abutment.  This 3-digit GPS point was used to survey the coordinates of 4-digit check points 3042 through 3046 chosen to evaluate the post-processed “bare earth” LIDAR data accuracy in different vegetation categories.
Although it correctly served its intended purpose in calibrating other check points, GPS point 106 is a good example of a survey point that should not itself be selected as a check point.  When interpolating the LIDAR points that surround point 106, the interpolations would be performed using LIDAR points that are off the bridge, down at the water’s edge, and, therefore, could falsely indicate that the LIDAR elevations are in error when the LIDAR elevations could be very accurate.

## Bench Marks

- Replace Reference Marks (RM) shown on old style FIRMs
- Three types:

- Identified by their NSRS Permanent IDentifier (PID)

## Jones County- 2003 Mapping

**Jones County- 2003 Mapping**

**Blue = 2003 **
**Zone AE**

**Cross Section**

**BFE**

## The Boundaries

**The Boundaries**

**2002 Detail Mapping **
**vs. **
**Effective Approximate Mapping**

## Effective vs 2002 Mapping

- Old Zone A Boundary (red)

- 2002 Limited Detail Boundary (blue)

**Effective vs 2002 Mapping**

## Features of New Maps

## Vertical Datum Information

- Explains vertical offset from NGVD 29 to NAVD 88
- “County Average Vertical Datum Offset Table” displays datum offset by county

## Flood Warning SystemHow it  works

**Rain Gage**

**Stream Gage**

## Collection of High Water Marks (HWM)

**Collection of High Water Marks (HWM)**

- NHMS supported these activities in NC

**NHMS Project Areas**

**North Carolina****HARN**

## Slide 22

## Monitoring Subsidence

**Monitoring Subsidence**

## Education Outreach

**Education Outreach**

**GPS Training Workshop:** is a traveling workshop designed for government agencies, professional surveyors, academic departments, school groups, and other interested parties in North Carolina.

- Workshops are tailored to each group’s respective needs
- PDH credit

## Questions?