Title: From netCDF to GIS
1From netCDF to GIS
- David R. Maidment
- Unidata Program Center, Boulder CO
- 6 Feb 2004
2NetCDF and GIS
- NetCDF describes atmospheric and water properties
varying continuously in (x,y,z,t) - GIS describes the physical landscape,
- Vector GIS has spatially discrete features
(point, line area) - Raster GIS is spatially continuous (in 2D)
- How do we connect the water with the water
environment
3NetCDF File for Model Output
dimensions lat 5, lon 10, level 4, time
unlimited variables float rh (time, lat,
lon) int lat(lat), lon(lon) latunits
degrees_north longunits
degrees_east short time(time)
timeunits hours since 1996-1-1 data lat
20, 30, 40, 50, 60 long -160, -140, -118,
-96, -84, -52, -45, -35, -25, -15 time
12 rh .5,.2,.4,.2,.3,.2,.4,.5,.6,.7,
.1,.3,.1,.1,.1.,.1,.5,.7,.8,.8,
.1,.2,.2,.2,.2,.5,.7,.8,.9,.9,
.1,.2,.3,.3,.3,.3,.7,.8,.9,.9
.0,.1,.2,.4,.4,.4,.4,.7,.8,.9
4Relative Humidity Points
5Interpolate to Raster
GeoTiff format, cell size 0.5ยบ
6Zoom in to the United States
7Average Rh in each State
Determined using Spatial Analyst function Zonal
Statistics with Rh as underlying raster and
States as zones
8Unidata Toolbox
Relative Humidity Analysis Model
Created in Arc 9 Model Builder
9Model Output Geodatabase
(Grids)
Geodatabase
Feature Dataset
Feature class
Feature class
Raster Catalog
Relationship
Raster
Table
Table
10Raster Catalog has Types of Data
11Scenarios for Data Dissemination
- ArcSDE and ArcIMS
- Leveraging the Unidata Local Data Manager (LDM)
- Access through Unidata Internet Data Viewer (IDV)
- Direct downloads from ArcGIS
12Scenario 1 ArcIMS ArcSDE
- Underlying data are stored in a relational
database (e.g. Oracle) - Accessed through Arc Spatial Data Engine (ArcSDE)
- Web access through Arc Internet Map Server
(ArcIMS) - Used for National Elevation Dataset, National
Land Cover Dataset, National Hydrography Dataset - Suitable for large static databases
- Possibly a good approach for historical climate
datasets, e.g. VEMAP (NCAR Nan Rosenbloom, Dave
Schimel, Tim Kittel)
National Elevation Dataset
13Scenario 1 ArcIMS ArcSDE
- User Experience
- Go to a web site, browse available data and
select a geographic region and desired data
themes - Download means that a data product is created
off-line and user is notified by email when it is
ready - If lt 100MB download via ftp for free
- If gt 100MB write to CD-ROM and mail ()
- Contacts Paul Wiese, USGS, Denver (NHD) Sue
Greenlee, USGS, EROS Data Center (NED, NLCD)
National Elevation Dataset
14Scenario 2 Leverage the LDM
- File is disseminated through LDM network e.g.
netCDF format - Unidata publishes an Arc Toolbox for converting
file (or adds a decoder to LDM to convert to
Grid) - Good for GIS analysis of existing real time data
stream
15Scenario 3 Access through IDV
- IDV is used to browse remote datasets
- Protocol to access Geography Network is added to
IDV - Geographic data added to IDV displays
- Atmospheric data converted to GeoTIFF for GIS
analysis - Build Raster Catalog of atmospheric datasets
Data Publisher 1
Data Publisher 4
Data Publisher 2
Data Publisher 3
Meteorologix publishes atmospheric data on the
Geography Network
16Scenario 4 Direct Downloads from ArcGIS
- Select region and time period
- Launch query to http// access
- Download data
- Import to geodatabase
- Run models
Nexrad data for July 30, 2001, Rosillo Creek
17Nexrad for Rosillo Creek
18GIS in Water Resources Consortium
Water Resources
- Bringing together these two communities by using
a common geospatial data model
19Arc Hydro Hydrography
20Arc Hydro Hydrology
21Arc Hydro Framework Data Model
22Arc Hydro Framework For South Florida
Basins
Waterbody (NHD)
Hydro Points
National Hydrography Dataset, NHD
23Arc Hydro Components
24Connecting Arc Hydro and Hydrologic Models
Interfacedata models
GIS
HMS
Geo Database
Arc Hydro data model
RAS
WRAP
25Nexrad Map to Flood Map in Arc 9 Model Builder
Flood map as output
Model for flood flow
HMS
Model for flood depth
Nexrad rainfall map as input
26Time and Space in GIS
Time Series
Feature Series
t3
t2
Value
t1
Time
Raster Series
Attribute Series
Value
t3
t2
t1
t1
t2
t3
y
x
27Time Series and Temporal Geoprocessing
DHI Time Series Manager
Time Series
Feature Series
t3
t2
Value
t1
Time
Raster Series
Attribute Series
Value
t3
t2
t1
y
x
ArcGIS Temporal Geoprocessing
28Time series from gages in Kissimmee Flood Plain
- 21 gages measuring water surface elevation
- Data telemetered to central site using SCADA
system - Edited and compiled daily stage data stored in
corporate time series database called dbHydro - Time series downloaded from dbHydro and stored
for all gages as Arc Hydro Attribute Series
29Arc Hydro Attribute Series
Map features have a time varying attribute
HydroID 2906
Feature Class (HydroID)
Attribute Series Table (FeatureID)
30Raster Series
Ponded Water Depth Kissimmee River June 1, 2003
31Arc Hydro Attribute Series Object
TSDateTime
Feature Class (point, line, area)
TSValue
FeatureID
TSType
TSType Table
32NetCDF Data Model
Time
Dimensions and Coordinates
Value
Space (x,y,z)
Variable
Attributes
33Conclusions
- Good time to make progress
- Unidata THREDDS research done at Unidata and some
experience accumulated - Arc 9.0 is about to be released with Model
Builder planning for Arc 9.1 about to begin - Fairly sound understanding of how to develop time
series in ArcGIS - Lots of cool weather and climate data that we
really, really would like to use more!!