Streamgage Streamgage Datum Datum
ConversionConversionHeight Modernization Height Modernization
Coordination teleconferenceCoordination teleconference
February 9, 2012February 9, 2012
Jim Kolva, Office of Surface Jim Kolva, Office of Surface WaterWater
Topics for DiscussionTopics for Discussion
Problem from USGS Water Problem from USGS Water perspectiveperspective
Database FactsDatabase Facts How Height Modernization might help How Height Modernization might help
the conversion effort?the conversion effort?
ProblemProblem
Most USGS streamgages have a Most USGS streamgages have a datum surveyed or estimated to datum surveyed or estimated to NGVD29. NGVD29.
Streamgages established since Streamgages established since 2002 and surveyed using a Global 2002 and surveyed using a Global Positioning System (GPS) should Positioning System (GPS) should have datum set to NAVD88.have datum set to NAVD88.
ProblemProblem
ProblemProblem
ProblemProblem
ProblemProblem Mixing vertical Datums creates Mixing vertical Datums creates
confusion;confusion; This mixture of Altitude Datums has This mixture of Altitude Datums has
created a confusing situation for created a confusing situation for streamgage information users streamgage information users attempting to model flood plain attempting to model flood plain inundation, establish flood profiles or inundation, establish flood profiles or use other hydrologic applications.use other hydrologic applications.
In some areas of the country, the In some areas of the country, the difference between NGVD29 and difference between NGVD29 and NAVD88 can be over NAVD88 can be over 4 feet4 feet..
Partner Applications of Partner Applications of Information – NWS AHPSInformation – NWS AHPS
Partner Applications of Partner Applications of Information – NWS AHPSInformation – NWS AHPS
USGS/NWS/FEMA Flood USGS/NWS/FEMA Flood Inundation InitiativesInundation Initiatives
Policy Guidance from Policy Guidance from USGSUSGS
NAVD88 is the recommended NAVD88 is the recommended datum established in the Federal datum established in the Federal Geographic Data framework Geographic Data framework (Office of Water Information (Office of Water Information Technical memorandum Technical memorandum 2002.01).2002.01).
Database factsDatabase facts
84,944 Surface-Water sites84,944 Surface-Water sites 62,032 determined elevation from Maps62,032 determined elevation from Maps 7,737 from Levels7,737 from Levels 8,023 unknown source8,023 unknown source 1,269 from a GPS1,269 from a GPS
4,771 already reported to 4,771 already reported to NAVD88NAVD88
Database factsDatabase facts
84,944 Surface-Water sites84,944 Surface-Water sites 62,032 determined elevation from Maps62,032 determined elevation from Maps Convert these to NAVD88 directly Convert these to NAVD88 directly
because within existing accuracy because within existing accuracy limitations unless a determination of limitations unless a determination of need for more accuracy due to data use.need for more accuracy due to data use.
Database factsDatabase facts
125 sites in NGS database 125 sites in NGS database (NGSIDB)for NAVD88 have a “gage” (NGSIDB)for NAVD88 have a “gage” description. description. Assumed to be USGS streamgagesAssumed to be USGS streamgages Additional sites may be present but did Additional sites may be present but did
not show up in the searchnot show up in the search Approximately 17,000 sites need to Approximately 17,000 sites need to
have some analysis and conversion.have some analysis and conversion.
NGS assistance in GPS NGS assistance in GPS surveyssurveys
NGS is doing updating work and NGS is doing updating work and GPS surveys throughout the countryGPS surveys throughout the country North Carolina and Michigan -- Will North Carolina and Michigan -- Will
survey in at least one reference mark at survey in at least one reference mark at active gages in work areasactive gages in work areas
Working on best ways to easily provide Working on best ways to easily provide reference mark descriptions and gage reference mark descriptions and gage locations to contractors doing this work locations to contractors doing this work and best way to report back to USGS.and best way to report back to USGS.
Priority stationsPriority stations
USGS, NGS, USACE and NWS developing USGS, NGS, USACE and NWS developing priority lists of gages for conversionpriority lists of gages for conversion Pilot study in MissouriPilot study in Missouri
MO has been working with Darrell Pratte, MO has been working with Darrell Pratte, NGS Geodetic Coordinator with the Missouri NGS Geodetic Coordinator with the Missouri DNR. Darrell has volunteered to serve in a DNR. Darrell has volunteered to serve in a role of oversight for field surveys and provide role of oversight for field surveys and provide some personnel.some personnel.
Plan was developed for conversion of gages in Plan was developed for conversion of gages in Missouri. Includes survey plans for those Missouri. Includes survey plans for those stations identified as needing that level of stations identified as needing that level of attention. attention.
Priority stationsPriority stations
David Ulrey of USACE is working on the David Ulrey of USACE is working on the same effort for their streamgages. Some same effort for their streamgages. Some gages are common to both agencies so gages are common to both agencies so David and Paul Rydlund (USGS) will be David and Paul Rydlund (USGS) will be coordinating. (Comprehensive Elevation coordinating. (Comprehensive Elevation of Project Datum – CEPD).of Project Datum – CEPD).
There is generally a lot of interest when There is generally a lot of interest when this is discussed with other agencies and this is discussed with other agencies and organizations. People see the need even organizations. People see the need even if they don’t have the resources. if they don’t have the resources.
Priority stationsPriority stations
USGS, USACE, NOS and NWS developing USGS, USACE, NOS and NWS developing priority lists of gages for conversionpriority lists of gages for conversion Pilot study in Coastal TexasPilot study in Coastal Texas
TCOON (Texas Coastal Ocean Observation Network) TCOON (Texas Coastal Ocean Observation Network) and Texas A&M--Corpus Christiand Texas A&M--Corpus Christi
Seeking funding to upgrade USGS sites to meet NOS Seeking funding to upgrade USGS sites to meet NOS tidal gage standards, both NAVD88 and local tidal tidal gage standards, both NAVD88 and local tidal datum.datum.
Next “beta” areas are the North Next “beta” areas are the North Atlantic coast and the Great LakesAtlantic coast and the Great Lakes
Funding SourcesFunding Sources
Unfunded mandate to USGS Water Unfunded mandate to USGS Water Science CentersScience Centers
Some will need GPS surveys to meet Some will need GPS surveys to meet required accuracies or because of required accuracies or because of instability issues.instability issues.
Can the Height Mod efforts partner Can the Height Mod efforts partner with the USGS efforts?with the USGS efforts?
Issues to be resolvedIssues to be resolved
Accuracy of the conversion.Accuracy of the conversion. ResourcesResources
Time and manpowerTime and manpower MoneyMoney
Data already converted to Data already converted to elevation in database – Florida elevation in database – Florida effortsefforts
Questions and Questions and Comments??Comments??
