OGC WCS: A Short Guide - Europa€¦ · Web Coverage Service (WCS) = - modular, testable, scalable ... EO-WCS WCS Application Profile for Earth Observation [OGC 10-140] - 2D imagery

Peter Baumann

Jacobs University | rasdaman GmbH

baumann@rasdaman.com

OGC WCS: A Short Guide

[gamingfeeds.com]

Overview

Introduction

Coverage data: the OGC Coverage Model

Coverage services: the WCS Suite

Conformance Testing

Summary

Features & Coverages

The basis of all: geographic feature

- = abstraction of a real world phenomenon [OGC, ISO]

Special kind of feature: coverage

- = space-time varying multi-dimensional phenomenon

Usually, Big Geo Data are coverages

Coverage Data & Services

coverage = digital representation of some space-time verying phenomenon

- n-D, discretized or continuous, testable down to pixel level

- uniform handling of space & time

Web Coverage Service (WCS) =

- modular, testable, scalable

- Core mission: Get original data (or subset thereof), suitable for further processing

Starting WCS 2, coverage data & service model separated

- Coverages servable by WFS, WMS, WCS, WCPS, WPS, SOS, ...

- WCS, WCPS specialized on coverages

feature coverage

images data

(Part of) The OGC Standards Quilt

• WMS "portrays spatial data pictures"

• WCS: "provides data + descriptions; data with original semantics,

may be interpreted, extrapolated, etc.“

[09-110r3]

Overview

Introduction

Conformance Testing & Implementations

Summary

Coverage Definition

class GML 3.2.1 Application Schema for Coverages

«FeatureType»

Coverage

«FeatureType»

GML::Feature

«Union»

GML::DomainSet

«Union»

GML::RangeSet

«type»

SWE Common::DataRecord

rangeSetdomainSet rangeType

contains hook

for metadata

ISO 19123

is abstract

→ many different

implementations

possible

→ not per se

interoperable

OGC coverage std

is concrete and

interoperable

[OGC 09-146r2]

from SWE Common

MultiSolid

Coverage

OGC Coverage Types

Coverage = digital representation of

space/time varying phenomenon

- n-D!

«FeatureType»AbstractCoverage

MultiPoint

Coverage

MultiCurve

Coverage

MultiSurface

Coverage

Referenceable

GridCoverage

as per GML 3.2.1

Rectified

GridCoverage

Coverage Subtypes

GridCoverage:

- Obsoleted, should not be used

for referenced data

RectifiedGridCoverage:

- Grid which is equidistant, straight

- Georeferenced

- Ex: ortho imagery, climate data cubes

ReferenceableGridCoverage

- Grid may not be equidistant, not straight

- May not be georeferenced

- Ex: L0 satellite data, curved grids,

triangular meshes, hexagonal grids

Gridded Coverage Types

Not georeferenced, „just pixels“

- GMLCOV::GridCoverage

Georeferenced, regular

- GMLCOV::RectifiedGridCoverage

Georeferenced, 1+ irregular axes

- All axes irregular: GML 3.3

ReferenceableGridByVectors *

- GMLCOV::ReferenceableGridCoverage

Georeferenced, 1+ axes warped

- All axes warped: GML 3.3 ReferenceableGridByArray *

- GMLCOV::ReferenceableGridCoverage

[Campalani 2013]

*) CR to GML planned

Mix, eg, with

sat image

timeseries

Sample Grid Coverage (GML)

samples for each coverage type

provided with specification bundle

Sample MultiSolidCoverage

Coverage Encoding

Pure GML: complete coverage, in GML

Special Format: other suitable file format (ex: MIME type “image/tiff”)

Multipart-Mixed: multipart MIME, type “multipart/mixed”

GML Coverage

Domain set

Range type

Range set

App Metadata

GML Coverage

Domain set

Range type

App Metadata

NetCDF file

NetCDF

Domain set

Range type

Range set

App Metadata

GeoTIFF

Domain set

Range type

Range set

App Metadata

Sample Mixed Encoding: TIFF

Content-Type: Multipart/Related; boundary=wcs;

start="GML-Part"

type="text/xml"

Content-type: text/xml

Content-ID: GML-Part

<?xml version="1.0" …>

<gmlcov:RectifiedGridCoverage …>

<gml:domainSet>…</gml:domainSet>

<gml:rangeSet>

<gml:File>

<gml:rangeParameters xlink:href="grey.tif"

xlink:role="http://www.opengis.net/spec/WCS_coverage-encoding_geotiff/1.0/"

xlink:arcrole="fileReference"/>

<gml:fileReference>grey.tif</gml:fileReference>

<gml:fileStructure/>

<gml:mimeType>image/tiff</gml:mimeType>

</gml:File>

</gml:rangeSet>

<gmlcov:rangeType>…</gmlcov:rangeType>

</gmlcov:RectifiedGridCoverage>

Content-Type: image/tiff

Content-Description: coverage data

Content-Transfer-Encoding: binary

Content-ID: grey.tif

Content-Disposition: INLINE

...binary TIFF data...

--wcs--

How to request

a particular encoding

from a server?

See later!

Adding Metadata To Coverages

Coverage has slot „metadata“ allowing to link in <any> kind of metadata

- WCS will deliver this, even without knowing contents

Ex: EO-WCS

GetCoverage

result

Inverse possible, too:

metadata record

contains (or links)

coverage

Overview

Introduction

Summary

WCS Core

WCS Service Model: Structure

Hook for future service-

related coverage metadata

WCS offering

can be seen as

a single virtual

document

Notwithstanding

other actual

encodings

[OGC 09-110r4]

GML coverage

WCS Service Model: Operations

GetCapabilities

- what service extensions?

- What formats? CRSs?

- What coverages?

DescribeCoverage

- coverage metadata

GetCoverage

- coverage, or subset thereof

Web Coverage Service (WCS)

WCS Core: Simple & efficient access to n-D coverages & subsets

- Format conversion on the fly

- subset = trim | slice

WCS Extensions: for optional functionality facets

WCS Application Profiles: domain-oriented bundling

- EO, MetOcean, ...

WC GetCoverage: Retrieve Coverage (Subset)

Download a coverage (or a subset thereof), values guaranteed unchanged

Ex: „download coverage c001“

Ex: „coverage c001, lat/long cutout, time slice t=2009-11-06T23:20:52Z”

Ex: “coverage c001, in GeoTIFF”

http://www.acme.com/wcs ? SERVICE=WCS & VERSION=2.0

& REQUEST=GetCoverage & COVERAGEID=c001

& SUBSET=Long(100,200) & SUBSET=Lat(50,60)

& SUBSET=phenomenon-time("2009-11-06T23:20:52Z")

& REQUEST=GetCoverage & COVERAGEID=c001 & FORMAT=“image/tiff“

WCS Suite Big Picture

WCS Extensions

WCS Extension – Range Subsetting [OGC 12-039]

Extract range components

- „bands“, „variables“

- Extension to GetCoverage request

& RangeSubset=red

…& RangeSubset=nir,red,green &…

…& RangeSubset=green,red,blue &…

…& RangeSubset=nir:green &…

…& RangeSubset=band01,band03:band05,band19:band21 &…

WCS Extension - Scaling [OGC 12-039]

Reduce resolution of gridded coverages

2.0 = scale DOWN by factor of 2

Interpolation control depending on Interpolation extension

& ScaleByFactor=2.0 &…

…& ScaleAxesByFactor=lat(2.0),long(2.0),time(1.0) &…

…& ScaleToSize=lat(4000),long(5000) &…

…& ScaleToExtent=lat(10,20),long(20,30) &…

WCS Extension – Interpolation [OGC 12-049]

Communicate & control interpolation to be applied

- Scaling, CRS

Cap doc reports interpolation methods supported

- Without IE: opaque,

server doesn„t tell

Client can mandate

particular method

http://www.acme.com/wcs ? SERVICE=WCS & VERSION=2.0 & REQUEST=GetCoverage & COVERAGEID=c001 & ...

& INTERPOLATION=http://www.opengis.net/def/interpolation/OGC/1/linear

<int:InterpolationMetadata>

<int:InterpolationSupported>

http://www.opengis.net/def/interpolation/OGC/0/nearest-neighbor

</int:InterpolationSupported>

<int:InterpolationSupported>

http://www.opengis.net/def/interpolation/OGC/0/linear

</int:InterpolationSupported>

</int:InterpolationMetadata>

…& INTERPOLATIONPERAXIS=phenomenon-time,http://www.opengis.net/def/interpolation/OGC/1/nearest-neighbor

WCS Extension – CRS [OGC 11-053]

retrieval (& bbox) in CRSs different from Native CRS

- Capabilities document lists supported CRSs (must be at least 1)

This needs

- New CRSs (vertical, time, index, proxies, ...) Time + Index CRS NTS

- Combination of CRSs CRS NTS

& SUBSETTINGCRS=http://www.opengis.net/def/crs/EPSG/0/4326

& OUTPUTCRS=http://www.opengis.net/def/crs/EPSG/0/4326

Time & Index CRSs [OGC 13-102r2]

Need new CRSs / axes:

- Time (incl calendars) Temporal.DWG

- Vertical new WG

- Index („ImageCRS“, never formalized) Index CRS

NB: EPSG not interested in time CRSs

Issue: ISO timestamps as coordinates

- WCS allows, GML (still) refuses

Ex: http://www.acme.com/wcs

? SERVICE=WCS & VERSION=2.0 & REQUEST=GetCoverage

& COVERAGEID=C0002

& SUBSET=long(100,200)

& SUBSET=lat(50,60)

& SUBSET=phenomenon-time("2009-11-06T23:20:52Z")

CRS Name Types [OGC 11-135] WGS84, RESTful:

• http://www.opengis.net/def/crs/EPSG/0/4326

WGS84, KVP:

• http://www.opengis.net/def/crs?authority=EPSG&version=0&code=4326

Parametrized („AUTO“) CRSs:• http://www.opengis.net/def/crs?authority=OGC&version=1.3

& code=AUTO42003 & UoM=m & CenterLongitude=-100 & CenterLatitude=45

Ad-hoc combination of CRSs:• http://www.opengis.net/def/crs-compound?

1=http://www.opengis.net/def/crs/EPSG/0/4326& 2=http://www.opengis.net/def/crs/ISO/2004/8601

Proprietary CRS definition:• http://www.acme.com/def/this-is-EPSG-4326

Inline CRS definition:• srsName=“#crsdef”

OGC resolver implementation

provided by Jacobs U:

www.earthlook.org/demos/secore

WCS Extension – Transaction [OGC 13-057]

= WCS-T: Modify coverage offerings on a server via Web

- New requests:

InsertCoverage + DeleteCoverage + UpdateCoverage (partial replacement)

- Core design goal: GetCoverage InsertCoverage

Revamping old WCS-T 1.1.4 (Arliss Whiteside) 2.0

- Adjusted to GMLCOV & WCS 2.0

Ex: http://www.acme.com/wcs

? SERVICE=WCS & VERSION = 2.0

& REQUEST=InsertCoverage

& COVERAGEREF=http://bcme.com/archive/hurricane.nc

& USEID=new

WCS Extension – Processing [OGC 13-057]

WCS wrapper for OGC Web Coverage Processing Service (WCPS)

- high-level spatio-temporal geo raster query language

for $c in ( M1, M2, M3 )where

some( $c.nir > 127 )return

encode($c.red - $c.nir,“image/tiff“

(tiffA,

tiffC)

"From MODIS scenes M1, M2, M3: difference between red & nir, as TIFF"• …but only those where nir exceeds 127 somewhere

Application Profiles

EO-WCS

WCS Application Profile for Earth Observation [OGC 10-140]- 2D imagery + time metadata

- hierachical coverage groupings

- Metadata & provenance

- Mosaic overlaying

EO Metadata Record 1

EO Metadata Record 2

[JacobsU, EOX]

MetOcean-WCS [OGC 14-052]

WCS Application Profile for Meteorology, Climate, Aviation

Data model:

- 4-D x/y/z/t data cubes

Service model:

- Space-time extraction

- curtains, corridors

Status: draft

- JacobsU + UK MetOffice

[UK MetOffice, DWD]

WPS AP – Coverages [OGC 09-045r1]

Specialization of WPS for coverage services

- WCS folks: „want to have async processing on coverages“

- WPS folks: „want interoperable coverage processes“

WCS request type

WPS process definition

- WCS extensions piggyback

- No new schema needed

<wps:Execute …

xsi:schemaLocation="http://www.opengis.net/wps/2.0.0 ../wpsExecute.xsd"

service="WPS" version="2.0.0" response="document” mode="async">

<ows:Identifier>http://my.wps.server/processes/wcs</ows:Identifier>

<wps:Input id="GetCoverageRequest">

<wcs:CoverageId>MyLittleCoverage</wcs:CoverageId>

<wcs:trimDimension>

<wcs:dimension>Long</wcs:dimension>

<wcs:trimLow>20</wcs:trimLow>

<wcs:trimHigh>29</wcs:trimHigh>

</wcs:trimDimension>

</wps:Input>

<wps:Output id="GetCoverageResponse“ …>

</wps:Output>

</wps:Execute>

Overview

Introduction

Summary

Conformance Testing: Status

WCS Implementations

High acceptance by implementers for WCS 2

- "The WCS 2.0 XML schema set is much easier to use than the 1.x XML; it

validates and is better organized" -- OPeNDAP

Users increasingly planning to move to WCS 2 (eg, NGA)

Known implementations:

- rasdaman, MapServer, GeoServer, OPeNDAP, GMU, Trellis, ...

- rasdaman WCS Core Reference implementation

WCS & WCPS: Practice Proven

from simple data access to agile analytics on spatio-temporal sensor,

image, simulation, & statistics data

130+ TB databases, 2D, 3D x/y/z & x/y/t, 4D x/y/z/t timeseries

single query distributed to 1,000+ cloud nodes

„raster data manager“: SQL + n-D raster objects

Scalable parallel “tile streaming” architecture

In operational use

- OGC Web Coverage Service

Core Reference Implementation

rasdaman: Agile Array Analytics

select img.green[x0:x1,y0:y1] > 130

from LandsatArchive as img

where avg_cells( img.nir ) < 17

Adaptive Tiling

Sample tiling strategies [Furtado]:

- regular directional area of interest

rasdaman storage layout language

insert into MyCollection

values ...

tiling area of interest [0:20,0:40], [45:80,80:85]

tile size 1000000

index d_index storage array compression zlib

Inset: WaterML 2.0 Time Handling

WaterML 2.0: timseries = time slices

OGC Coverages: time just another axis «FeatureType»Coverage

«Union»DomainSet

«Union»RangeSet

«type»DataRecord

rangeSetdomainSet rangeType

Sample Application: Database Visualization

for $s in (SatImage), $d in (DEM)

return

encode(

struct {

red: (char) s.image.b7[x0:x1,x0:x1],

green: (char) s.image.b5[x0:x1,x0:x1],

blue: (char) s.image.b0[x0:x1,x0:x1],

alpha: (char) scale( d.elev, 20 )

"image/png"

[JacobsU, Fraunhofer; data courtesy BGS, ESA]

Viewing: WCPS Emulating WMS

Example 2: real-time WMS zoom/pan/styling

- 1 background, 1 bathymetry, 3*RGB

- www.earthlook.org

SELECT png(

(marray x in [0:399,0:399] values {255c,255c,255c})

overlay

((scale( extend( img0[269:349,0:65], [269:395,-60:65] ), [0:399,0:399] ) < -1300)*{0c,0c,0c}

+(-1300.000000< scale( extend( img0[269:349,0:65], [269:395,-60:65] ), [0:399,0:399] ) and scale( extend( img0[269:349,0:65], [269:395,-60:65] ), [0:399,0:399] ) <= -1290)*{219c,0c,172c}

+(-1274.999999< scale( extend( img0[269:349,0:65], [269:395,-60:65] ), [0:399,0:399] ) and scale( extend( img0[269:349,0:65], [269:395,-60:65] ), [0:399,0:399] ) <= -1272.5)*{186c,0c,189c}

+ (-126.5 < scale( extend( img0[269:349,0:65], [269:395,-60:65] ), [0:399,0:399] ))*{255c,255c,255c})

overlay (scale( extend( img2[124:468,0:578], [124:717,-14:578] ), [0:399,0:399] ))

overlay (scale( extend( img3[11375:11578,0:120], [11375:11968,-473:120] ), [0:399,0:399] )) )

FROM Hakon_Bathy AS img0, Hakoon_Dive1_8 AS img1, Hakoon_Dive2_8 AS img2, Hakoon_Dive2b_8 AS img3

for $a in (A), $b in (B), $c in (C), $d in (D)

return

max(($a.nir - $a.red) / ($a.nir + $a.red))

- max(($b.nir - $b.red) / ($b.nir + $b.red))

- max(($c.nir - $c.red) / ($c.nir + $c.red))

- max(($d.nir - $d.red) / ($d.nir + $d.red))

Parallel / Distributed Query Processing

1 query 1,000+ cloud nodes

Dataset B

Dataset A

Dataset D

Dataset C

Use Case: Plymouth Marine Laboratory

“Avg chlorophyll concentration for given area & time period, from x/y/t cube”

- 10, 60,120, 240 days

Conclusions:

- „we must minimise data transfer

as well as [client] processing”

- “standards such as WCPS provide

the greatest benefit”

[Oliver Clements, EGU 2014]

rasdaman

Secured Archive Integration

First-ever direct, ad-hoc mix from protected NASA & ESA services

in OGC WCS/WCPS Web client (EarthServer + CobWeb)

Real Life, Real Volume, Real Service

6 Lighthouse Applications covering Earth & Planetary Sciences

Established data centers adding EarthServer technology to service

portfolio

Summer 2014: all 20+ TB, 2x 100+ TB = 280 TB operational

ChartLink

- Envitia Ltd, UK

rasdaman

- Jacobs U,

rasdaman GmbH

petascope

rasdaman

WCS+WCPS WPS+WCPS

Viewing: WPCS for Web Mapping

[ESA VAROS project, 2010]

Overview

Introduction

Summary

WCS goes ISO

Resolved at OGC TC meeting in Calgary, Sep 2014:

Submission of OGC coverage works to TC211 as DIS

- GMLCOV

- WCS Core

- WCS POST/XML

Rationale: Interoperability & sustainability of coverage data & services

- GMLCOV also preparing/initiating revision of 19123

- WCS 2.0 as the missing TC211 Web Coverage Service

ISO 9075 Part 15: SQL/MDA

- resolved by ISO SQL WG in June 2014

- Based on rasdaman concepts & experience

n-D arrays as attributes

declarative array operationsselect id, encode(scene.band1-scene.band2)/(scene.nband1+scene.band2)), „image/tiff“ )

from LandsatScenes

where acquired between „1990-06-01“ and „1990-06-30“ and

avg( scene.band3-scene.band4)/(scene.band3+scene.band4)) > 0

Science SQL in ISO

create table LandsatScenes(

id: integer not null, acquired: date,

scene: row( band1: integer, ..., band7: integer ) array [ 0:4999,0:4999] )

SWE, SOS: upstream

sensor data capturing

W*S: downstream

download, processing, visualization

WPS...coverage

server

Conclusion Coverage data = spatio-temporal regular & irregular grids, point clouds, meshes

- GMLCOV, based on ISO 19123

- Servable by many services

Web Coverage Service: from simple access to versatile analytics- Uniform interface to grids, point clouds, [meshes tbd]

- Scalable implementations: 130+ TB, 1000+ cloud nodes

OGC WCS: A Short Guide - Europa€¦ · Web Coverage Service (WCS) = - modular, testable, scalable ... EO-WCS WCS Application Profile for Earth Observation [OGC 10-140] - 2D imagery

Documents

Cisco Wireless Control System（WCS） - Cisco - …...

Designing Testable Software

Learning k-testable and k-piecewise testable languages from....

Service Oriented Architecture (SOA) An Interoperable Web...

Writing Testable Code

Scaling data access in Visual Weather - ECMWF · 2017. 3......

introducing cisco wcs and cisco wcs navigator

Standards-based Access to Air Quality Data: Application of.....

Simple testable code

Publikation OGC Metadateneditor mit gvSIG · UMN MapServer....

Interoperability between OGC CS/W and WCS Protocols ·...

Introduction to ArcGIS GIS Server & Web GIS Applications ·...

Integrating Weather Data with GIS: the draft OGC WCS...

gvSIG – DesktopGIS und Client für GDI€¦ · OGC WMS,.....

Creating Testable Questions

INSPIRE Download Service profile of OGC Web Coverage...