Make A Graph

Dataset Title:	Chlorophyll a Concentration, Aqua MODIS - 8-day, 2002-present. v.2018.0
Institution:	NASA/GSFC OBPG (Dataset ID: aqua_chla_8d_2018_0)
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 1.025784e+9, 1.6514064e+9;
    String axis "T";
    String ioos_category "Time";
    String long_name "Centered 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";
    Float32 _FillValue NaN;
    Float32 actual_range -89.97917, 89.97916;
    String axis "Y";
    String ioos_category "Location";
    String long_name "Latitude";
    String standard_name "latitude";
    String units "degrees_north";
    Float32 valid_max 90.0;
    Float32 valid_min -90.0;
  }
  longitude {
    Int32 _ChunkSizes 8640;
    String _CoordinateAxisType "Lon";
    Float32 _FillValue NaN;
    Float32 actual_range 0.0208387, 359.9792;
    String axis "X";
    String ioos_category "Location";
    String long_name "Longitude";
    String standard_name "longitude";
    String units "degrees_east";
    Float32 valid_max 360.0;
    Float32 valid_min 0.0;
  }
  chlor_a {
    Float32 _FillValue NaN;
    Float64 colorBarMaximum 30.0;
    Float64 colorBarMinimum 0.03;
    String colorBarScale "Log";
    String ioos_category "Ocean Color";
    String long_name "Chlorophyll Concentration, OCI Algorithm";
    String references "Hu, C., Lee Z., and Franz, B.A. (2012). Chlorophyll-a algorithms for oligotrophic oceans: A novel approach based on three-band reflectance difference, J. Geophys. Res., 117, C01011, doi:10.1029/2011JC007395.";
    String standard_name "mass_concentration_of_chlorophyll_in_sea_water";
    String units "mg m-3";
    Float32 valid_max 100.0;
    Float32 valid_min 0.001;
  }
  NC_GLOBAL {
    String _lastModified "2022-05-25T02:25:31.000Z";
    String _NCProperties "version=2,netcdf=4.7.3,hdf5=1.12.0,";
    String cdm_data_type "Grid";
    String Conventions "CF-1.6 ACDD-1.3, COARDS";
    String creator_email "data@oceancolor.gsfc.nasa.gov";
    String creator_name "NASA/GSFC/OBPG";
    String creator_type "group";
    String creator_url "https://oceandata.sci.gsfc.nasa.gov";
    String date_created "2019-02-13T02:50:25Z";
    Float64 Easternmost_Easting 359.9792;
    Float64 geospatial_lat_max 89.97916;
    Float64 geospatial_lat_min -89.97917;
    Float64 geospatial_lat_resolution 0.04166666589488307;
    String geospatial_lat_units "degrees_north";
    Float64 geospatial_lon_max 359.9792;
    Float64 geospatial_lon_min 0.0208387;
    Float64 geospatial_lon_resolution 0.041666669903924064;
    String geospatial_lon_units "degrees_east";
    String history 
"Wed May 25 07:10:28 2022: ncatted -O -a sw_point_longitude,global,o,f,0.02083333 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:28 2022: ncatted -O -a geospatial_lon_min,global,o,f,0.0 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:28 2022: ncatted -O -a geospatial_lon_max,global,o,f,360.0 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:28 2022: ncatted -O -a easternmost_longitude,global,o,f,360.0 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:28 2022: ncatted -O -a westernmost_longitude,global,o,f,0.0 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:28 2022: ncatted -O -a valid_max,lon,o,f,360.0 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:28 2022: ncatted -O -a valid_min,lon,o,f,0.0 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:25 2022: ncap2 -O -s where(lon<0) lon=lon+360 A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
Wed May 25 07:10:23 2022: ncks -O --msa_usr_rdr -d lon,0.0,180.0 -d lon,-180.0,0.0 A20221212022128.L3m_8D_CHL_chlor_a_4km.nc A20221212022128.L3m_8D_CHL_chlor_a_4km-0-360.nc
l3mapgen par=A20221212022128.L3m_8D_CHL_chlor_a_4km.nc.param 
2023-03-20T21:55:50Z (local files)
2023-03-20T21:55:50Z https://oceanwatch.pifsc.noaa.gov/griddap/aqua_chla_8d_2018_0.das";
    String id "A20221212022128.L3b_8D_CHL.nc/L3/A20221212022128.L3b_8D_CHL.nc";
    String identifier_product_doi "10.5067/AQUA/MODIS/L3M/CHL/2018";
    String identifier_product_doi_authority "https://dx.doi.org";
    String infoUrl "https://oceandata.sci.gsfc.nasa.gov";
    String institution "NASA/GSFC OBPG";
    String instrument "MODIS";
    String keywords "algorithm, aqua, biology, center, chemistry, chlor_a, chlorophyll, chlorophyllr, color, concentration, data, earth, Earth Science > Oceans > Ocean Chemistry > Chlorophyll, Earth Science > Oceans > Ocean Chemistry > Chlorophyllr, Earth Science > Oceans > Ocean Chemistry > Pigments > Chlorophyll, flight, goddard, group, gsfc, image, imaging, L3, level, level-3, mapped, mass, mass_concentration_of_chlorophyll_in_sea_water, moderate, modis, modisa, nasa, obpg, ocean, ocean color, oceans, oci, palette, pigments, processing, resolution, science, sea, seawater, smi, space, spectroradiometer, standard, water";
    String keywords_vocabulary "GCMD Science Keywords";
    String l2_flag_names "ATMFAIL,LAND,HILT,HISATZEN,STRAYLIGHT,CLDICE,COCCOLITH,LOWLW,CHLWARN,CHLFAIL,NAVWARN,MAXAERITER,ATMWARN,HISOLZEN,NAVFAIL,FILTER,HIGLINT";
    String license "https://science.nasa.gov/earth-science/earth-science-data/data-information-policy/";
    String map_projection "Equidistant Cylindrical";
    String measure "Mean";
    String naming_authority "gov.nasa.gsfc.sci.oceandata";
    String NCO "netCDF Operators version 4.7.5 (Homepage = http://nco.sf.net, Code = https://github.com/nco/nco)";
    Int32 nco_openmp_thread_number 1;
    Float64 Northernmost_Northing 89.97916;
    String platform "Aqua";
    String processing_level "L3 Mapped";
    String processing_version "2018.1QL";
    String product_name "A20221212022128.L3m_8D_CHL_chlor_a_4km.nc";
    String project "Ocean Biology Processing Group (NASA/GSFC/OBPG)";
    String publisher_email "data@oceancolor.gsfc.nasa.gov";
    String publisher_name "NASA/GSFC/OBPG";
    String publisher_type "group";
    String publisher_url "https://oceandata.sci.gsfc.nasa.gov";
    String sourceUrl "(local files)";
    Float64 Southernmost_Northing -89.97917;
    String spatialResolution "4.64 km";
    String standard_name_vocabulary "CF Standard Name Table v36";
    String summary "Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua - 8-day Ocean Color. Chlorophyll-a Concentration. 2002 - present. spatial resolution = 4.64km";
    String temporal_range "8-day";
    String time_coverage_end "2022-05-01T12:00:00Z";
    String time_coverage_start "2002-07-04T12:00:00Z";
    String title "Chlorophyll a Concentration, Aqua MODIS - 8-day, 2002-present. v.2018.0";
    Float64 Westernmost_Easting 0.0208387;
  }
}

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.