Open Source Visualisation with ADAGUC Web Map Services

Open Source Visualisation with

ADAGUC Web Map Services

Maarten Plieger

Ernst de Vreede

John van de Vegte, Wim Som de Cerff, Raymond Sluiter, Ian van der Neut, Jan Willem Noteboom

KNMI – ADAGUC 2

ADAGUC project

Cooperative project finished end of 2009

Dissemination of atmospheric data to GIS community

OGC webservices (WMS,WCS) for data in NetCDF4/HDF5 files

Web portal:

Layers from several services

Download data through WCS interface

WMS/WCS service component

ADAGUC Product Standard for metadata; storage in NetCDF4/CF

Demo site:

http://adaguc.knmi.nl

A good start!

Atmospheric Data Access

for the

Geographical information system to visualize

netCDF files via the web

• Web Map Service and Web Coverage Service • Developed at KNMI (2009 till present)

• Server: C++ application

• Viewer/Client: JavaScript application • NetCDF4, HDF5 and OpenDAP

• Multi dimensional data supported!

• Can serve true color data (1 byte per channel, RGBA)

• Very fast nearest neighbour reprojection (C++) • Both open source since 2013!

https://dev.knmi.nl/projects/adaguc/

ADAGUC server and viewer software

Atmospheric Data Access

for the

KNMI – ADAGUC 4

Web Map Services: From data to images

NetCDF Data

(big, 5.5Gb)

PNG images

(small, 180Kb)

Combined

geographically

+

Introduction to OGC services

OGC – Open Geospatial Consortium

currently ~450 organizations

standards for geospatial content and services GIS data sharing and processing

Services used within the ADAGUC project:

ADAGUC: Atmospheric Data Access for the Geospatial User Community, finished in 2009) Web Map Service (WMS) - for images

Web Feature Service (WFS) - for vector data (features) Web Coverage Service (WCS) - for raster data (coverages)

WMS is primarily for visualization

KNMI – ADAGUC

Web Map Service – for visualizations

6

Generates visualizations of geospatial data in the form of 2D images, suitable

for transfer over the internet (JPG/PNG/GIF)

• REST based:

– Compose an URL with key value pairs, and you will get an image!

• Standard is developed and maintained by the Open Geospatial Consortium

• Generated images are geo-referenced

– Images from several sources can be easily combined • Images have dimensions

– Time, elevation, member

• WMS services can be viewed in many web based clients – OpenLayers, Leaflet, GoogleMaps, ADAGUC viewer, …

GetCapabilities

GetMap

GetLegendGraphic

GetFeatureInfo

WMS Requests - overview

GetCapabilities

GetMap

GetLegendGraphic

GetFeatureInfo

KNMI – ADAGUC 8

ADAGUC WMS Client: KNMI WMS viewer

Data from Globemission: NOx emissions from GOME-2

WMS GetCapabilities WMS GetMap WMS GetFeatureInfo WMS GetLegendGraphic

Web Coverage Service – WCS (similar to WMS)

Similar to WMS, but returns data instead of images

Returns observations in a regular spaced grid in many projections Generates data in geotiff, ascii, netcdf 3/4, HDF5, etc…

KNMI – ADAGUC

ADAGUC Viewer WCS Client

Atmospheric data – what’s so special?

Observations in space and time

Point data for example observing stations

Gridded data for example satellite or precipitation radar

Model data: forecasts in time and space, usually starting from a

certain “reference time”

Usually gridded data (“fields”)

Multidimensional data:

Atmosphere is a 3D structure Time makes 4D

Reference time makes 5D Ensembles make 6D

KNMI – ADAGUC [email protected] OGC

12

Used data format: NetCDF4-CF

NetCDF4 with Climate and Forecast conventions (CF conventions)

– Standard names, standard units (http://cf-pcmdi.llnl.gov/documents/cf-standard-names/) – Identify and compare data

– Locate data in space–time as a function of other independent coordinate variables (time, latitude and longitude):

KNMI – ADAGUC

Projected grids

KNMI – ADAGUC

Point data

KNMI – ADAGUC

True color RGBA images in NetCDF – using uint type

OPeNDAP – for data access and subsetting

• OPeNDAP is the name of the organization and the name of the protocol

• Open-source Project for a Network Data Access Protocol

• Data is stored at remote server

• Data model is similar to NetCDF’s data model (with differences)

• N-dimensional array container, with variables, dimensions and attributes

• Only requested pieces of data are sent

• Accessing small pieces of large files on a remote server can still be quick • Data is requested based on sub-setting along dimensions

• OPeNDAP resources can be opened locally on your computer as if it were local

files using the NetCDF library

• Local files versus remote files is transparent

• The concept of a file is gone, an OPeNDAP endpoint can represent thousands of

files aggregated along a dimension

• E.g. Usually concatenate a large time series observation to one endpoint using the time dimension

KNMI – ADAGUC

Data standards

Work done on client

Work done on server

Array based data

Graphics

WMS

(de Boer & Plieger, 2014)

Data files

HTTP / FTP

Referenced data

WCS

KNMI – ADAGUC 22

Projection, resizing & subsetting

Meteosat HRVIS:

Satellite view projection

Resolution: 3520 x 4660

Radar precipitation:

Polar stereographic projection

Resolution: 700 x 765

Combined in Dutch Rijksdriehoekstelsel projection

KNMI – ADAGUC 24

Questions?

Thanks all for

watching!