GEON IDV Plots of GPS Data
The GEON IDV can display GPS velocities, with vectors and error ellipses, on any scale and map projection, and overlay the velociy plots on other geophysical data, imagery, and map data.
GPS velocity vectors may have 2 components (east and north), or 3 components including vertical, and with the IDV you can plot GPS vectors in 3D.
The IDV can also display time series of GPS station position displacements (north, east and vertical components).
PBO GPS Velocities
click to see full size
Data for the latest GPS velocities in the PBO list of stations, the
combined products from the GPS Analysis Center at MIT (the best quality results;
from the PBO data file "pbo.final_frame.vel") are available for IDV use
online at URL
http://geon.unavco.org/unavco/GPS/pbo_final_frame_vel_2008_08_07.idv.csv.
You can use this data source to plot GPS velocity vectors, station 4 character names at locations, or both.
There are 983 stations in this data set.
These vectors are relative to the North American reference frame.
To load this data source into the IDV, first "copy link location" for that URL. Enter that link location in the URLs entry box in the IDV Dashboard's Data Choosers window. Be sure to first choose Data Source Type of "Text Point Data Files." Click on Add Source. Then make a "Point Data" display. The IDV reads the data from the UNAVCO GEON server; the file is not copied to your system.
Sample IDV displays:
PBO velocity data set; GPS stations coverage area (selected stations from more than 950)
PBO Pacific Northwest GPS velocities, relative to North American plate
PBO velocities, western US, low oblique, including vertical motions
Details about this data are available from the The PBO web site and PBO GPS Products.
"GPS Vel 1.0 ITRF 2000" Velocities
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The GPS velocities and error ellipse data from the
UNAVCO GPSVEL working group, global solution version 1.0, ITRF 2000, are available from
http://geon.unavco.org/unavco/GPS/GPSVEL_1.0_ITRF2000.nc.
Be sure to use Data Source Type of "NetCDF Point Data" in the Dashboard's Data Chooser.
About the GPS VEL project see GPSVEL, GPSVEL Products, and GPSVEL Project: Towards a Dense Global GPS Velocity Field
Note these vectors are relative to a no net rotation Earth surface reference frame.
Sample IDV displays:
GPSVEL 1.0: U.S. plot
GPSVEL 1.0: global plotPBO GPS Station Time Series
click to see full size
You can plot time series from GPS stations in the IDV, for the PBO nretwork and a few others around the globe. You click on the station symbol on the map, for the station of interest.
Time series data files for the PBO stations, formatted to work in the IDV, are online at PBO Time Series files for the IDV There are 1255 stations. Use an IDV station plot, as shown above (in "PBO GPS Velocities"), to find the names of the stations of interest to you. In the list of PBO Time Series files for the IDV do "copy link location" for a station file of interest. Enter that link location in the URLs entry box in the IDV Dashboard's Data Choosers window. Be sure to first choose Data Source Type of "Text Point Data Files." In future we hope to provide a way for you to click a station on a map and see the IDV time series display for that station.
Create a "Point Data Plot" display. In its display control, do View->Undock from Dashboard. Click on the Plot tab. Now you can resize the plot by resixzing the window. In the map display, click on the symbol at the station where you want to see the time series. In the display's control, Plot panel, you should see the station name and location appear in a list below the chart; DOUBLE click on a variable name (in that same list as the station name) to plot the time series of that variable.
Do a right click on each variable name in the list to remove, or add, that variable to the time series plot. Do View->Chart->Chart:(chart title)->Zoom In->Domain Axis to zoom in along the time axis (shorter time range). To add a title to the plot, right click on the time series plot, choose mednu choice Properties. In the Name entry box add your title. To save an image of the chart, do View->Chart->Chart:(chart title)->Save chart as.
Sample IDV displays:
SLAC regional stations and GPS velocities
SLAC time series
In this time series plot for SLAC you can see strong northward motion, from -60 mm on 1/104
to +50 mm on 1./1/08, or 27 mm per year northward, and westward motion at the same rate.
Formatting PBO GPS Time Series Files for the IDV
If you are a customay IDV user you do not deed to do this. It has been done already.
The source of time series data for these GPS stations, is PBO GPS Products amd "save target as" for the "Position Time Series" link. This is a gzip-tar file. Unpack the file to see lots of the .csv files, one for each station. The header lines must be reformatted to work in the IDV.
To modify a PBO station time series data file to use in the IDV, the header lines such as PBO Station Position Time Series Format Version,1.0.1 4-character ID,ELKO Station name,ELKO_BRGN_NV1997 Begin Date,2004-01-07 End Date,2008-07-28 Release Date,2008-07-30 Reference position,40.9146904918 North Latitude,-115.8171979278 East Longitude,2016.89028 meters elevation, Date,North (mm),East (mm),Vertical (mm),North Std. Deviation (mm),East Std. Deviation (mm),Vertical Std. Deviation (mm),Quality, (from ELKO.pbo.csv) are replaced with 2 lines describing the data character and 4 lines about the station. Do not alter the caps as in Latitude (index) -> (Longitude,Latitude,Altitude,Time,Station(Text),North,East,Vertical,Nstddev,Estddev,Vstddev,Quality(Text)) Longitude[unit="degrees east"],Latitude[unit="deg"],Altitude[unit="meter"],Time[fmt="yyyy-MM-dd"],Station(Text),North[unit="mm"],East[unit="mm"],Vertical[unit="mm"],Nstddev[unit="mm"],Estddev[unit="mm"],Vstddev[unit="mm"],Quality(Text) Longitude=-115.8171979278 Latitude=40.9146904918 Altitude=2016.89028 Station=ELKO_BRGN_NV1997 You might name the new file ELKO.pbo.idv.csv.Here is a sample PBO time series file for the IDV, witrh two stations, ELKO and TRND.
Making Displays - more details
First set the display to a map projection (map area) and a vertical scale suitable for your data. If you are only showing data on the surface, in overhead views, the vertical scale does not matter.
Connect to a data source with the "GEON IDV Dashboard" window, "Data Chooser" tab. For local files choose the "Files" section, navigate to the file on your local disk, choose the Data Type from the pull down menu, and click "Add source." For data sources with an HTTP server, use section "URLs." If your data is in a .csv file, use Data Type "I'm feeling lucky" which means the IDV recognizes the data type from the file name extension. If your data file is a NetCDF (.nc) file, choose Data Type "NetCDF Point Data files."
After you connect to a data source the Dashboard shows the "Field Selector" for that data. To make a display, in general you choose (click on) a Field name in the "Field Selector" tabbed panel in the Dashboard, then click on a display type in the Displays panel of the same window, and then click on the "Create Display" button.
GPS station data is Field type "Point Data," and the Displays panel shows the choice "Point Data Plot" and "Point Data List." Click on one, then click on the "Create Display" button.
When a display is made the Dashboard shows the "display control" panel for that display. Note the pull down menu called "Layout Model" or "Station Model" which is a list of the plot symbols available for all kinds of data. At first a Point Data Plot display will use plot symbols called "Locations 3D Cross," or whatever happens to be first in the "Layout Model" list. To use another plot symbol, choose one from the list. For GPS velocity vectors, use "GPS Vectors, red" or GPS Vectors, black." You need the GEON IDV plugin of March 6, 2007 to get both colors and vertical components. Get the latest plugin from the GEON IDV download page.
You can control vector length scaling, using the "Scale" entry box in the Display control window that pops up when the display is made. The Declutter check box reduces the number of symbols in the display. Read more about Point data plots and Working with the Point data Plot Symbols using "Layouts Models"
To zoom, pan, and rotate see Zoom, pan and rotate.
Comments or questions about this page? Send e-mail to Stuart
Wier (wier
unavco.org).
