Google Earth: A New Display Tool for Hydrologic Data Sets

Brian CosgroveBrian CosgroveNOAA/NWS/OHDNOAA/NWS/OHD

OutlineProject motivation and background Google Earth overviewStrategies for importing XMRG/HRAP data into

GEConversion strategies for non-HRAP/XMRG dataxmrgtokml conversion utilityExample GE images using xmrgtokml outputAdditional GE hydrologic visualizationsSummary

MotivationModern computing and observation systems have

created an explosion of hydrologic data setsNOAA/OHD faces sizable visualization challenges

Distributed Hydrologic Model Threshold Frequency (DHM-TF) Flash Flood Modeling Approach

High resolution 4km XMRG output on HRAP grid No intuitive, accessible means of visualizing data

Additional XMRG/HRAP hydrological modeling data sets A clear need exists for accessible and accurate

visualization of hydrologic observation and forecast dataResearch Goal: Create a means of visualizing

XMRG/HRAP data sets with potential applicability to other data projections

Visualizing Hydrologic Data

GrADS

MATLAB

NOAA/OHD data sets(XMRG file format, HRAP coordinate system)

Best Visualization Strategy?

Google EarthAdvantages

Extremely intuitive, accessible, and free

Displays how data sets line up with real-world features (i.e., roads, buildings, rivers, vegetation, mountains)

Aerial and street-level views

Time lapse imagesUser-drawn place

marks and polygonsAvailability of KML

dataWeb-linked datasetsAutomatic updates

DisadvantagesNo data processing

capabilityLimited layer managementNo control of title, color barLatitude Longitude

projection with a WGS84 datum for its imagery base

HRAP data needs to be processed before ingest

Potential precision, accuracy and coordinate system mismatch between GE and data (being investigated)

Slow display of polygonsKML file format

Google EarthNOAA has an enterprise license

agreement for unlimited use of GE Pro

GE data files need to be in Keyhole Markup Language (KML) format, and can be zipped into KMZ format

KML: A tag-based language like HTML

Specify icons and labels, image overlays

Create different camera positions Write HTML descriptions with

hyperlinks and embedded images Dynamically update remote KML

files

http://www.nites.noaa.gov/bpa/display.asp?bpaID=14

EXAMPLE KML

<?xml version="1.0“ encoding="UTF-8"?> <kml xmlns="http://earth.google.com/kml/2.2"> <Placemark> <name>Stonehenge, England</name> <description>Stonehenge Point </description> <Point> <coordinates>-1.8267,51.1790 </coordinates> </Point> </Placemark> </kml>

Google Earth Screenshot

U.S. Capitol Building

Herd of African Elephants

Model-based Flash Flood Return Periods

Challenge: Use a program often associated with aerial views of landmarks and nature to make detailed hydrologic data accessible to end users

Strategies for Importing XMRG/HRAP data into Google Earth

Question: How to display XMRG formatted HRAP data sets in Google Earth?

Approach: Convert data to KML format with a Latitude Longitude projection

Two possible methodsConvert each HRAP pixel into a clickable

HRAP polygon for display in GEInterpolate HRAP data to lat/lon, create

image file, overlay image in GE

Clickable Polygon Method

Accurately reproduces value of HRAP pixelVery small error in straight line HRAP pixel outlineClickable to display HRAP coordinates and data valueKML file size can be prohibitively large for areas

bigger than an RFC domain

Repeat for all HRAP cells

*Calculate Lat/Lon of HRAP cell

corners

Original data on HRAP grid

View KML in Google Earth

Produce title and color bar

Draw polygon in KML and assign value and color

40,-98

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*Reverse of the code used in the NEXRAD software that takes data from the radar processing system and projects it into HRAP

Interpolated Image File Method

File size is much smaller than polygon methodShaded or contour line styles can be selectedFlexibility in spatial resolution of interpolated dataInterpolated data values differ from original HRAP pixelsAreas along domain boundaries may be clippedIndividual pixels cannot be queried

Interpolation and Lat/Lon

bound specification with GrADS

Original data on HRAP grid

Graphical image on Lat/Lon grid

Image overlay in Google Earth

Produce title and color bar

Strategies for Importing XMRG/HRAP data into Google Earth

Techniques developed explicitly to address display of NOAA/OHD XMRG/HRAP flash flood data

Can also display other HRAP data setsGeneral conversion techniques can be adapted for

display of other data projectionsClickable Polygon Method

Requires method of computing Lat/Lon of pixel corner points

Interpolated Image Method Requires that GrADS be able to convert between

projections Alternatively, any program can be used that converts

between projections and determine Lat/Lon bounds needed for KML

Importing XMRG data into GE: xmrgtokmlProgram produces KML file needed by Google Earth to

display XMRG/HRAP data (clickable polygon or image interpolation)

xmrgtokml ingests XMRG header information describing HRAP grid Functions with various HRAP resolutions (1, 0.5, 0.25 HRAP) Errors in XMRG header can lead to display errors

Program has several requirements xmrgtoasc and a2png conversion utilities, luxisr.ttf font, Linux zip

utilityUser is able to specify several options, including subset

bounds, contour levels, a customized title, pixel outlines, and other options

Limitations xmrgtokml is in early Alpha development stage Feedback will be essential for bug repairs and capability

enhancements As previously noted, issues with datum compatibility, accuracy,

precision are being investigated

Notice: xmrgtokml requires xmrgtoasc utility, luxisr.ttf, zip utility, convert utility, and a2png program Enter input HRAP filename to be converted to KML formattair1231200618z Enter base output file name (will be applied to KML, legend, and title files)tair1231200618z Enter title for plot (leave blank for no title)DMIP2 Air Temperature Enter min and then max values on separate lines or leave blank for automatic range3050 Enter min hrapx, max hrapx, min hrapy, and max hrapy on separate lines or leave blank for full domain plot

Enter Plot Style: 1 for flat polygons, 2 for extruded polygons, 3 for shaded image file, 4 for contour image file (Extruded often looks best, but flat should be used if terrain is turned on in Google Earth. Image files are best for large domains)2 Draw pixel outlines? 1-Yes 0-No1 Display non-positive values? 1-Yes 0-No1 ----------------------------------------- ncols nrows,xll,yll,nodata,cellsize 48 39 61 429 -1.000000 1.000000 ----------------------------------------- min,max,increment 30.00000 50.00000 2.500000 ----------------------------------------- level 2 = 30.00000 level 3 = 32.50000 level 4 = 35.00000 level 5 = 37.50000 level 6 = 40.00000 level 7 = 42.50000 level 8 = 45.00000 level 9 = 47.50000 level 10 = 50.00000 -----------------------------------------hrapx,hrapy,xsize,ysize,x,y 61.00000 429.0000 48 39 -340.0000 -1172.000 ----------------------------------------- wrote tair1231200618z.nointerp.kmz wrote tair1231200618z.legend.png wrote tair1231200618z.title.png

Soon to be available upon request

xmrgtokml screen dialog

PROJCS["Stereographic",GEOGCS["Unknown",DATUM["D_unknown",SPHEROID["Unknown",6371200,"inf"]],PRIMEM["Greenwich",0], UNIT["Degree",0.017453292519943295]],PROJECTION["Polar_Stereographic"],PARAMETER["latitude_of_origin",60], PARAMETER["central_meridian",-105], PARAMETER["scale_factor",1], PARAMETER["false_easting",401], PARAMETER["false_northing",1601],UNIT["meters",4762.5]]

Importing Shapefiles into Google Earth

Google Earth Pro can automatically convert and display ESRI Shapefiles

Most files are converted without troubleHRAP projection Shapefiles require

special .prj file

Contents of .prj file needed for displaying HRAP Shapefiles

Using xmrgtokml: Example Images From Google Earth

Clickable Polygon Versus Interpolated Image Method

-XMRG/HRAP DMIP2 Temperature-

Clickable Polygon

Interpolated Image(Contour and Shaded)

Clickable Polygon Versus Interpolated Image Method

Interpolated Image (Shaded)

Interpolated Image (Shaded)

Clickable Polygons

•Sacramento XMRG/HRAP Lower Zone Tension Water Maximum (LZTWM) parameter

• Opaque/semi-transparent Sacramento LZTWM overlay with no pixel outlines

• Google Earth default base map

• Bird’s eye as well as tilted perspective view

Google Earth Viewing Perspectives

•MPE, HPE, and HPN precipitation data (XMRG format and HRAP coordinate system) displayed with clickable polygon method•Google terrain background

0-1 Hour HPN Forecast (mm) 23Z April 21st to 00Z April 22nd 2009

HPE Precipitation (mm) 23Z April 21st to 00Z April 22nd 2009MPE Precipitation (mm) 23Z April 21st to 00Z April 22nd 2009

1-2 Hour HPN Forecast (mm) 23Z April 21st to 00Z April 22nd 2009

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• Opaque precipitation overlay with no pixel outlines

• Google Terrain base map

• User-specified min/max contour intervals

HPE Precipitation (mm) – ¼ HRAP Resolution

• Opaque precipitation overlay with no pixel outlines

• Google Terrain base map

• PowerPoint image loop

XMRG/HRAP HPN and HPE Precipitation Data

Beyond xmrgtokml: Utilizing Google Earth’s Capabilities to Visualize Additional Hydrologic Data Sets

DMIP2 temperature forcing data Carson and American River basin outlines from DMIP2 shape file Semi-transparent temperature overlay with pixel outlines drawn Clickable temperature map Google Terrain base map

Combining HRAP Data with GIS Shapefiles

• Opaque (left) /semi-transparent (right) HRAP precipitation overlay with no pixel outlines

• WFO boundary overlay from shapefile (in white, left)

• Google Earth default base map

• Clickable precipitation data

Combining HRAP Data with GIS Shapefiles

• Opaque DMIP2 precipitation overlay with no pixel outlines

• SNOTEL station locations from point-type shape file

• Google Earth default base map

Combining HRAP Data with GIS Shapefiles

Combining HRAP Data with Warning and Verification Data—Combining HRAP Data with Warning and Verification Data—Tropical Storm HannaTropical Storm Hanna

Depiction of the areas covered by the three Tropical Storm Hanna flash flood warnings (outlined in Red) issued by the Sterling WFO that lie within the Maryland DHM-TF case study domain. Figure also depicts maximum return period values from DHM-TF covering a similar time period.

Maximum return period values from MPE-driven DHM-TF simulated during the period of time from 16Z on September 6th through 02Z on September 7th 2008. Spotter-confirmed flash flood events are indicated by the Blue wave symbols

ESRI Shapefile: HRAP RFC Boundaries

• RFC basin shapes from HRAP shapefile

• Google Earth default base map

April 2nd, 2009: Red River Floods

SNODAS 06Z Model SWE

MODIS 19:30Z Visible Image(White=snow)

( on map)

• Georeferenced aerial photo

• MODIS and SNODAS image overlays

• Wild Rice River basin shapefile outline

Integrating multiple sources of data with Google Earth

NOAA NOHRSC

• USGS gauge locations from KML file

• Clickable map is linked to USGS database

• Google Terrain base map

Using Google Earth to View USGS Gauge Data

Gauge Site Survey

• USGS gauge locations from KML file

• HRAP grid (Black) and Sacramento HRAP river network (White) from KML file

• Google Earth default base map

• Useful in routing parameter derivation

Upstream

Downstream

Millvale, PA Flash Flood, August 2007

On the morning of Wednesday, July 5, 2007 a flash flood rushed through Aliquippa's historical business district. The rainwater overwhelmed a culverted creek under Franklin Avenue, damaging over 500 buildings with water and mud in its wake.

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SummaryA clear need exists for accessible and accurate

visualization of hydrologic observation and forecast data

xmrgtokml utility developed to display NOAA/OHD DHM-TF and other HRAP data in Google Earth

Techniques presented are general enough to be adapted for use with non-HRAP data sets

Software is in Alpha stage, will be available in near future

Multiple issues remain to be addressed Coordinate system, precision, and accuracy issues Compatibility with other NOAA GIS resources Ongoing bug fixes