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Dataset Title:	Muskegon - Derived water quality parameters generated using the dynamically parameterized Color Producing Agents Algorithm (CPA-A).
Institution:	Michigan Tech Research Institute (Dataset ID: cppa_Muskegon)
Information:	Summary \| License \| FGDC \| ISO 19115 \| Metadata \| Background \| Data Access Form \| Files

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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:

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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 1.461772616e+9, 1.732637978e+9;
    String axis "T";
    Float64 fraction_digits 0;
    String ioos_category "Time";
    String long_name "Eastern 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 42.901, 43.398;
    String axis "Y";
    String ioos_category "Location";
    String long_name "Latitude";
    String standard_name "latitude";
    String units "degrees_north";
  }
  longitude {
    String _CoordinateAxisType "Lon";
    Float64 actual_range -86.699, -86.102;
    String axis "X";
    String ioos_category "Location";
    String long_name "Longitude";
    String standard_name "longitude";
    String units "degrees_east";
  }
  Chl_a {
    Float64 _FillValue -999.0;
    String ioos_category "Ocean Color";
    String long_name "Chlorophyll-a concentration EXPERIMENTAL";
    String standard_name "chlorophyll-a";
    String units "mg/m^3";
  }
  SM {
    Float64 _FillValue -999.0;
    String ioos_category "Unknown";
    String long_name "Suspended minerals concentration EXPERIMENTAL";
    String standard_name "suspended minerals";
    String units "mg/L";
  }
  ag443 {
    Float64 _FillValue -999.0;
    String ioos_category "Unknown";
    String long_name "CDOM absorption coefficient at 443 nm EXPERIMENTAL";
    String standard_name "ag(443)";
    String units "m^-1";
  }
  apg443 {
    Float64 _FillValue -999.0;
    String ioos_category "Unknown";
    String long_name "Non-water absorption coefficient at 443 nm EXPERIMENTAL";
    String standard_name "apg(443)";
    String units "m^-1";
  }
  bbp443 {
    Float64 _FillValue -999.0;
    String ioos_category "Unknown";
    String long_name "Particulate backscattering coefficient at 443 nm EXPERIMENTAL";
    String standard_name "bbp(443)";
    String units "m^-1";
  }
  NC_GLOBAL {
    String acknowledgement "Data courtesy of CoastWatch Great Lakes Node, Michigan Tech Research Institute under the project Leveraging New Satellite Assets to Improve Satellite and Modeling Tools for Monitoring and Prediction of Nearshore Water Quality in the Great Lakes, funded by the Great Lakes Restoration Initiative";
    String cdm_data_type "Grid";
    String contact_email "mjsayers@mtu.edu";
    String contact_name "Michael Sayers";
    String Conventions "COARDS, CF-1.10, ACDD-1.3";
    String creator_name "Michigan Tech Research Institute";
    String date_created "2026-04-16T18:36:18.523757Z";
    String description "Derived water quality parameters generated using the dynamically parameterized Color Producing Agents Algorithm (CPA-A).";
    Float64 Easternmost_Easting -86.102;
    Float64 geospatial_lat_max 43.398;
    Float64 geospatial_lat_min 42.901;
    String geospatial_lat_units "degrees_north";
    Float64 geospatial_lon_max -86.102;
    Float64 geospatial_lon_min -86.699;
    Float64 geospatial_lon_resolution 0.002999999999999971;
    String geospatial_lon_units "degrees_east";
    String grid_mapping_crs_wkt "GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]],AXIS[\"Latitude\",NORTH],AXIS[\"Longitude\",EAST],AUTHORITY[\"EPSG\",\"4326\"]]";
    String grid_mapping_GeoTransform "-86.7 0.003 0.0 43.4 0.0 -0.003";
    Float64 grid_mapping_inverse_flattening 298.257223563;
    String grid_mapping_long_name "CRS definition";
    Float64 grid_mapping_longitude_of_prime_meridian 0.0;
    String grid_mapping_name "latitude_longitude";
    Float64 grid_mapping_semi_major_axis 6378137.0;
    String grid_mapping_spatial_ref "GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]],AXIS[\"Latitude\",NORTH],AXIS[\"Longitude\",EAST],AUTHORITY[\"EPSG\",\"4326\"]]";
    String history 
"2026-06-02T03:00:31Z (local files)
2026-06-02T03:00:31Z https://apps.glerl.noaa.gov/griddap/cppa_Muskegon.das";
    String infoUrl "https://coastwatch.glerl.noaa.gov/";
    String institution "Michigan Tech Research Institute";
    String instrument "OLCI";
    String keywords "absorption, ag(443), ag443, agents, algorithm, apg, apg(443), apg443, backscattering, bbp, bbp(443), bbp443, cdom, Chl-a, chlorophyll, chlorophyll-a, coefficient, color, colored, concentration, cpa, cpa-a, data, derived, dissolved, dynamically, experimental, generated, institute, matter, michigan, minerals, non, non-water, ocean, ocean color, organic, parameterized, parameters, particulate, producing, quality, research, suspended, suspended minerals, tech, time, using, water";
    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.";
    String LongName "CPA-A derived parameters for Muskegon River Outflow using OLCI image from 07/22/2020 15:49:45";
    Float64 Northernmost_Northing 43.398;
    String platform "S3A";
    String ProductionDateTime "2026-04-16T18:36:18.523738Z";
    String ShortName "CPA-A outputs 20200722 154945";
    String sourceUrl "(local files)";
    Float64 Southernmost_Northing 42.901;
    String spatialResolution "0.003 degrees";
    String standard_name_vocabulary "CF Standard Name Table v70";
    String summary "Muskegon - Derived water quality parameters generated using the dynamically parameterized Color Producing Agents Algorithm (CPA-A).";
    String time_coverage_end "2024-11-26T16:19:38Z";
    String time_coverage_start "2016-04-27T15:56:56Z";
    String title "Muskegon - Derived water quality parameters generated using the dynamically parameterized Color Producing Agents Algorithm (CPA-A).";
    Float64 Westernmost_Easting -86.699;
  }
}

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[(2002-06-01T09:00:00Z)][(-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.