Streamgage datum conversion
Download
1 / 21

Streamgage Datum Conversion - PowerPoint PPT Presentation


  • 86 Views
  • Uploaded on

Streamgage Datum Conversion. Height Modernization Coordination teleconference February 9, 2012 Jim Kolva, Office of Surface Water. Topics for Discussion. Problem from USGS Water perspective Database Facts How Height Modernization might help the conversion effort?. Problem.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Streamgage Datum Conversion' - brygid


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Streamgage datum conversion

Streamgage Datum Conversion

Height Modernization Coordination teleconference

February 9, 2012

Jim Kolva, Office of Surface Water


Topics for discussion
Topics for Discussion

  • Problem from USGS Water perspective

  • Database Facts

  • How Height Modernization might help the conversion effort?


Problem
Problem

  • Most USGS streamgages have a datum surveyed or estimated to NGVD29.

  • Streamgages established since 2002 and surveyed using a Global Positioning System (GPS) should have datum set to NAVD88.





Problem4
Problem

  • Mixing vertical Datums creates confusion;

  • This mixture of Altitude Datums has created a confusing situation for streamgage information users attempting to model flood plain inundation, establish flood profiles or use other hydrologic applications.

  • In some areas of the country, the difference between NGVD29 and NAVD88 can be over 4 feet.





Policy guidance from usgs
Policy Guidance from USGS

NAVD88 is the recommended datum established in the Federal Geographic Data framework (Office of Water Information Technical memorandum 2002.01).


Database facts
Database facts

  • 84,944 Surface-Water sites

    • 62,032 determined elevation from Maps

    • 7,737 from Levels

    • 8,023 unknown source

    • 1,269 from a GPS

  • 4,771 already reported to NAVD88


Database facts1
Database facts

  • 84,944 Surface-Water sites

    • 62,032 determined elevation from Maps

    • Convert these to NAVD88 directly because within existing accuracy limitations unless a determination of need for more accuracy due to data use.


Database facts2
Database facts

  • 125 sites in NGS database (NGSIDB)for NAVD88 have a “gage” description.

    • Assumed to be USGS streamgages

    • Additional sites may be present but did not show up in the search

  • Approximately 17,000 sites need to have some analysis and conversion.


Ngs assistance in gps surveys
NGS assistance in GPS surveys

  • NGS is doing updating work and GPS surveys throughout the country

    • North Carolina and Michigan -- Will survey in at least one reference mark at active gages in work areas

    • Working on best ways to easily provide reference mark descriptions and gage locations to contractors doing this work and best way to report back to USGS.


Priority stations
Priority stations

  • USGS, NGS, USACE and NWS developing priority lists of gages for conversion

    • Pilot study in Missouri

      • MO has been working with Darrell Pratte, NGS Geodetic Coordinator with the Missouri DNR. Darrell has volunteered to serve in a role of oversight for field surveys and provide some personnel.

      • Plan was developed for conversion of gages in Missouri. Includes survey plans for those stations identified as needing that level of attention.


Priority stations1
Priority stations

  • David Ulrey of USACE is working on the same effort for their streamgages. Some gages are common to both agencies so David and Paul Rydlund (USGS) will be coordinating. (Comprehensive Elevation of Project Datum – CEPD).

  • There is generally a lot of interest when this is discussed with other agencies and organizations. People see the need even if they don’t have the resources.


Priority stations2
Priority stations

  • USGS, USACE, NOS and NWS developing priority lists of gages for conversion

    • Pilot study in Coastal Texas

      • TCOON (Texas Coastal Ocean Observation Network) and Texas A&M--Corpus Christi

      • Seeking funding to upgrade USGS sites to meet NOS tidal gage standards, both NAVD88 and local tidal datum.

    • Next “beta” areas are the North Atlantic coast and the Great Lakes


Funding sources
Funding Sources

  • Unfunded mandate to USGS Water Science Centers

  • Some will need GPS surveys to meet required accuracies or because of instability issues.

  • Can the Height Mod efforts partner with the USGS efforts?


Issues to be resolved
Issues to be resolved

  • Accuracy of the conversion.

  • Resources

    • Time and manpower

    • Money

  • Data already converted to elevation in database – Florida efforts



ad