Make A Graph

Dataset Title:	FTLE based on 5MHz HF Radar Network with 24-hour Integration Time
Institution:	Rutgers University (Dataset ID: FTLE_5MHz_24h)
Information:	Summary \| License \| FGDC \| ISO 19115 \| Metadata \| Background \| Data Access Form

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Graph Type:
X Axis:
Y Axis:
Color:

Dimensions

Start

Stop

time (UTC)

specify just 1 value →

latitude (degrees_north)

longitude (degrees_east)

Graph Settings
Color Bar:	Continuity:	Scale:
Minimum:	Maximum:	N Sections:
Draw land mask:
Y Axis Minimum:	Maximum:

(Please be patient. It may take a while to get the data.)

Optional:
Then set the File Type: (File Type information)
and

or view the URL:
(Documentation / Bypass this form

)

Click on the map to specify a new center point.

Zoom:

[The graph you specified. Please be patient.]

Things You Can Do With Your Graphs

Well, you can do anything you want with your graphs, of course. But some things you might not have considered are:

Web page authors can embed a graph of the latest data in a web page using HTML <img> tags.
Anyone can use ERDDAPs Slide Sorter to build a personal web page that displays graphs with the latest data (or other images or HTML content), each in its own, draggable slide.

The Dataset Attribute Structure (.das) for this Dataset

Attributes {
  time {
    String _CoordinateAxisType "Time";
    Float64 actual_range 1.35432e+9, 1.6724448e+9;
    String axis "T";
    String calendar "gregorian";
    String ioos_category "Time";
    String long_name "Time";
    String standard_name "time";
    String time_origin "01-JAN-1970 00:00:00";
    String units "seconds since 1970-01-01T00:00:00Z";
  }
  latitude {
    String _CoordinateAxisType "Lat";
    Float64 actual_range 33.54882049560547, 43.47378158569336;
    String axis "Y";
    String ioos_category "Location";
    String long_name "Latitude";
    String short_name "lat";
    String standard_name "latitude";
    String units "degrees_north";
  }
  longitude {
    String _CoordinateAxisType "Lon";
    Float64 actual_range -76.9767837524414, -68.033203125;
    String axis "X";
    String ioos_category "Location";
    String long_name "Longitude";
    String short_name "lon";
    String standard_name "longitude";
    String units "degrees_east";
  }
  ftle {
    Float64 _FillValue -999.0;
    String comment "24-hour integrated FTLE based on MARACOOS 5MHz HF radar network surface currents";
    String ioos_category "Time";
    String long_name "Finite Time Lyapunov Exponent";
    String units "1/hr";
  }
  NC_GLOBAL {
    String cdm_data_type "Grid";
    String comment "This product was developed as part of Jacqueline Veatch's PhD dissertation at Rutgers University";
    String contributor_name "Jacqueline Veatch, Josh Kohut, Erick Fredj, Delphine Mossman, Hugh Roarty, Laura Nazzaro, Michael Smith, Tim Stolarz";
    String contributor_role "Principal Investigator and Graduate Student, Advisor, Collaborator, Analyst, MARACOOS HF Radar Project Manager, Data Management, Data Management, Data Management";
    String Conventions "CF-1.10, ACDD-1.3, COARDS";
    String creator_email "nazzaro at marine.rutgers.edu";
    String creator_institution "Rutgers University";
    String creator_name "Laura Nazzaro";
    String creator_type "person";
    String creator_url "rucool.marine.rutgers.edu";
    Float64 Easternmost_Easting -68.033203125;
    Float64 geospatial_lat_max 43.47378158569336;
    Float64 geospatial_lat_min 33.54882049560547;
    Float64 geospatial_lat_resolution 0.03319384979962505;
    String geospatial_lat_units "degrees_north";
    Float64 geospatial_lon_max -68.033203125;
    Float64 geospatial_lon_min -76.9767837524414;
    Float64 geospatial_lon_resolution 0.03324751162617623;
    String geospatial_lon_units "degrees_east";
    String history 
"2025-10-18T14:14:57Z (local files)
2025-10-18T14:14:57Z http://hfr.marine.rutgers.edu/griddap/FTLE_5MHz_24h.das";
    String infoUrl "rucool.marine.rutgers.edu";
    String institution "Rutgers University";
    String keywords "24-hour, 5mhz, based, data, exponent, finite, frequency, ftle, HF, hf radar, hfr, hfradar, high, hour, integration, lyapunov, network, radar, rutgers, time, university, with";
    String license 
"The data may be used and redistributed for free but is not intended
for legal use, since it may contain inaccuracies. Neither the data
Contributor, ERD, NOAA, nor the United States Government, nor any
of their employees or contractors, makes any warranty, express or
implied, including warranties of merchantability and fitness for a
particular purpose, or assumes any legal liability for the accuracy,
completeness, or usefulness, of this information.";
    Float64 Northernmost_Northing 43.47378158569336;
    String publisher_email "nazzaro at marine.rutgers.edu";
    String publisher_name "Laura Nazzaro";
    String publisher_type "person";
    String publisher_url "rucool.marine.rutgers.edu";
    String references "Veatch et al 2025, https://github.com/jeixav/LCS-Tool-Article/";
    String sea_name "Mid-Atlantic Bight";
    String sourceUrl "(local files)";
    Float64 Southernmost_Northing 33.54882049560547;
    String standard_name_vocabulary "CF Standard Name Table v70";
    String summary "FTLE (Finite Time Lyapunov Exponent ) calculations begin with virtual particles released in a flow field. An FTLE ridge is then defined as an area where these particles are converged to and then diverged along. A scalar quantity is assigned to the FTLE ridge based on the integrated rate of attraction of the particles. These calculations were performed using a MATLAB toolbox modified to be applied to High Frequency Radar (HFR) and coastal flow. These modifications included (1) removal of the requisite for 'closed' structures, allowing the toolbox to identify 'filament' structures alone that are characteristic of coastal flow (2) assigning all NaN values to 24 hour periods with HFR coverage below 40% of the decade mean HFR coverage (3) aborting calculations when boundary conditions are not satisfactory (approaching +/- infinity) because the data being computed with is isolated (a small 'pond' of data) or advected particles are leaving the study region too quickly and (4) removing the 'edges' of the data where advected particles are influenced by the discontinuation of the data in an irregular shape.";
    String time_coverage_end "2022-12-31T00:00:00Z";
    String time_coverage_start "2012-12-01T00:00:00Z";
    String title "FTLE based on 5MHz HF Radar Network with 24-hour Integration Time";
    Float64 Westernmost_Easting -76.9767837524414;
  }
}

Using griddap to Request Data and Graphs from Gridded Datasets

griddap lets you request a data subset, graph, or map from a gridded dataset (for example, sea surface temperature data from a satellite), via a specially formed URL. griddap uses the OPeNDAP (external link)

Data Access Protocol (DAP) (external link)

and its projection constraints (external link)

The URL specifies what you want: the dataset, a description of the graph or the subset of the data, and the file type for the response.

(easy) You can get data by using the dataset's Data Access Form. It makes the URL for you.
(easy) You can make a graph or map by using the dataset's Make A Graph form. It makes the URL for you.
(not hard) You can bypass the forms and get the data or make a graph or map by generating the URL by hand or with a computer program or script.

griddap request URLs must be in the form
https://coastwatch.pfeg.noaa.gov/erddap/griddap/datasetID.fileType{?query}
For example,
https://coastwatch.pfeg.noaa.gov/erddap/griddap/jplMURSST41.htmlTable?analysed_sst[(2015-06-09T09:00:00Z)][(-89.99):1000:(89.99)][(-179.99):1000:(180.0)]
Thus, the query is often a data variable name (e.g., analysed_sst), followed by [(start):stride:(stop)] (or a shorter variation of that) for each of the variable's dimensions (for example, [time][latitude][longitude]).

For details, see the griddap Documentation.