Using Diva-on-web as a web-service

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Diva-on-web can be used as a web-service using the following GET or POST calls. The base_url is http://gher-diva.phys.ulg.ac.be/web-vis/Python/web/.

Contents

Upload

POST request to upload the data to be interpolated to the diva-on-web service. 

http://base_url/upload

Parameters

data
text file send to the server encoded as multipart/form-data. (see http://code.activestate.com/recipes/146306/ for an exemple in Python). The format of the fext file is described here.

Response

A simple XML file: 

<?xml version="1.0"?>
<stats>
  <! -- number of observations received -->
  <stat id='obs_count'>%d</stat>
  <! -- min longitude -->
  <stat id='obs_x0'>%g</stat>
  <! -- max longitude -->
  <stat id='obs_x1'>%g</stat>
  <! -- min latitude -->
  <stat id='obs_y0'>%g</stat>
  <! -- max latitude -->
  <stat id='obs_y1'>%g</stat>
  <! -- identifier of the session -->
  <stat id='sessionid'>%s</stat>
</stats>

The stats root element may contain a warning or an error element with a message if a problem occurred.

Analysis

GET request to make an analysis: 

http://base_url/make_analysis

Parameters

sessionid
id from previous upload
len
correlation length (arc degrees)
stn
signal to noise ratio (non-dimensional)
x0,x1,dx
first and last longitude values and resolution of the grid
y0,y1,dy
idem for latitude
level
depth level

Response

Returned XMS file: 

<?xml version="1.0"?>
<layers>
 <! -- identifier of the results -->
 <result src='%s' />
 <stats>
 <! -- minimum value of the analysis -->
 <stat id='vmin'>%g</stat>
 <! -- maximum value of the analysis -->
 <stat id='vmax'>%g</stat>
 <! -- number of observations used -->
 <stat id='stat_obs_count_used'>%g</stat>
 <stat id='stat_posteriori_stn'>%g</stat>
</stats>
</layers>


Download

GET request to download the results: 

http://base_url/download

Parameters

fieldname
identifier of the results

Response

The requested file in NetCDF format

Web Map Service

A graphical representation of the interpolated layer can also be requested using the WMS protocol. The layer name is composed by: 

 layer = fieldname + '#analyzed_field'

For example: 

http://gher-diva.phys.ulg.ac.be/web-vis/Python/web/diva_on_web?LAYERS=1234-efea26fb2_analysis_diva_gebco_20_2_-180_180_3_-72_87_3.nc%23analyzed_field&TRANSPARENT=true&FORMAT=image%2Fpng&STYLES=method%3Apcolor_flat%2Bncontours%3A40%2Binverted%3Afalse%2Bcmap%3Ajet%2Bvmin%3A-5.43691%2Bvmax%3A30.0554&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&SRS=EPSG%3A4326&BBOX=-180,-90,180,90&WIDTH=512&HEIGHT=256

The style attribute contains the following information:

method
plotting method (pcolor, contour or contourf)
ncontours
number of contours (ignored for pcolor)
inverted
true if color-map is inverted
cmap
color map name (http://www.scipy.org/Cookbook/Matplotlib/Show_colormaps)
vmin
minimum of color-map range
vmax
maximum of color-map range

Key and values are separated by a colon and key-value pairs by a plus sign. The style of the previous example is thus (decoded): 

method:pcolor_flat+ncontours:40+inverted:false+cmap:jet+vmin:-5.43691+vmax:30.0554


Python example

An example script in python.

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