14-021r2
6 Comparison of WMS Profiles
The following tables present the requirements of the WMS profiles against each operation offered by the service. Each row presents the requirements against the relevant operation and parameter in order to highlight the similarities and differences between the profiles. The phrase
“Supported as specified in the OGC WMS 1.3 Standard” has been used to indicate that the profile does not make changes to the requirement specified in the base standard.
6.1 GetCapabilities Operation
Table 1. WMS GetCapabilities operation comparison
Parameter or
Metadata element
Sub- element or
property NSG Profile Comment
DGIWG Profile Comment
1
UKMOD Profile Comment
1
Clarifications in this column were collected from the DGIWG meeting of February 2014
Copyright © 2014 Open Geospatial Consortium.
9 Service
Abstract Includes a security classification
identified at the top of the security field.
DGIWG profile requires a conforming WMS server to include the following
information in the abstract element of the service metadata: This service implements
the DGIWG WMS profile 1.3 version 1.0. Additional Clarification: Use of security
classification is allowable, but not mandatory in the DGIWG profile
Additional Clarification: “DGIWG determines, identification of source CRS and
transformation within the GetCapabilities Abstract to be an inappropriate location for
this information.” Requires inclusion of text
identifying the source CRS and transformation used.
Service Access
Constraints Populate the wms:AccessConstraints
element as you would the classification markings of a classified
document. This defines the highest classification level of the content
accessible through the WMS service. This may also include Fees.
Supported as specified in the OGC WMS 1.3 Standard, though likely to require support
for multinational classification systems. Additional clarification: “For the use of the
DGIWG profile in an NATO environment, the common NATO classification scheme
has to be applied.” Supported as specified in the
OGC WMS 1.3 Standard.
Service LayerLimit
Supported as specified in the OGC WMS 1.3 Standard.
If a DGIWG WMS server implements the LayerLimit parameter, it shall not be less
than 20. General
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Service MaxWidth
and MaxHeight
The MaxWidth and MaxHeight shall be greater or equal to 800 pixels.
The MaxWidth and MaxHeight shall be greater or equal to 800 pixels.
If omitted then MaxWidth and
MaxHeight imply no limit on the parameters. If
included MaxHeight and MaxWidth shall not be
less than 800. Layer
Abstract The Abstract element is not inherited
by child Layers. Supported as specified in the OGC WMS 1.3
Standard. The DGIWG profile however is not clear on
this and thus it is recommended that the profile be updated clarify the inheritance
requirements. Supported as specified in the
OGC WMS 1.3 Standard.
Style General
If only a single style is available, that style is known as the “default” style
and need not be advertised by the server. Style declarations are
inherited by child Layers. A child shall not redefine a Style with the
same Name as one inherited from a parent. A child may define a new
Style with a new Name that is not available for the parent Layer.
DGIWG profile states that “A DGIWG WMS server shall always provide at least
one style element even if only a default style is advertised.”
This profile mandates that a Named Layer must have at
least one Style element.
Style Format
Supported as specified in the OGC WMS 1.3 Standard.
DGIWG profile allows PNG, GIF or JPEG as a minimum.
Supported as specified in the OGC WMS 1.3 Standard.
Copyright © 2014 Open Geospatial Consortium.
11 EX_Geogra
phicBoundi ngBox
General Every named Layer shall have
exactly one EX_GeographicBoundingBox
element that is either stated explicitly or inherited from a parent Layer.
DGIWG profile is not clear on whether it requires the CRS of the
EX_GeographicBoundingBox to be stated explicitly or inherited from a parent layer.
Additional clarification: “The DGIWG WMS profile states no further requirement
as already defined in the base standard. Recommendation to update DGIWG profile
to clarify this aspect.” UKMOD profile mandates
that every Layer whether Named or Category must
have an explicit CRS for the layer.
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Copyright © 2014 Open Geospatial Consortium.
BoundingB ox
CRS The NSG provides the following
profiling instruction To be consistent with the DGIWG WMS
1.3 Profile, CRS elements shall be stated explicitly and not inherited
from a parent layer. The service shall support the following Coordinate
Reference Systems, and use the following associated keywords 1 to
designate them in its responses, and 2 to process the clients’ requests
[WGS84 geographic longitude, then atitude, expressed in decimal
degrees:CRS:84], [WGS84 geographic latitude, then longitude,
expressed in decimal degrees:EPSG:4326] and [World
Mercator projection:EPSG:3395]. The NSG also provides the following
profiling instruction Among the following Coordinate Reference
Systems, the service shall support all those which validity zone overlaps
data published by the service. For each of these Coordinate Reference
Systems, the following associated keywords shall be used 1 to
designate them in its responses, and 2 to process the clients’ requests
[UTM projections over WGS84 north zones: EPSG:32601 to
EPSG:32660], [UTM projections over WGS84 south zones:
EPSG:32701 to EPSG:32760], [UPS projection over WGS84 north zone:
j i
At a minimum, DGIWG profile requires support of EPSG:4326, EPSG:3395 and
CRS:84 In a Named Layer it is
appropriate Worldwide CRS are used in accordance with
the previous DGIWG WMS profile [7] and UTMUPS
projections which the layer data covers.
In addition to this it is recommended that for local
operations such as UK Operations which is
illustrated by the EPSG:27700 in the
example such projections or datums should be added
if the Named Layer data covers these CRS. When
adding CRS other than those based on WGS 1984 to a
Named Layer correct use of Geodetic Datum
Transformations must be applied as per OGC
document 09-187 and recorded in the Abstract
as described above.
Copyright © 2014 Open Geospatial Consortium.
13 BoundingB
ox minx miny
maxx maxy
If the Layer CRS is CRS:1 Map CS; see B.2, then
the BoundingBox units are pixels, the origin is at the upper left, the first x
axis increases to the right, and the second y axis increases toward the
bottom. Supported as specified in the OGC WMS 1.3
Standard. Supported as specified in the
OGC WMS 1.3 Standard.
MetadataU RL
General The wms:MetadataURL element
shall point to an NMIS instance document for that layer. That
document includes the ISM elements for that layer. The result is a
capabilities document with both an overall security marking and “portion
markings” at the layer level. It follows the conventions for
document marking so it will be intuitive to the user community.
See AccessConstraints above. The DGIWG WMS profile states no further
requirement as already defined in the base standard. Recommendation to update
DGIWG profile to clarify this aspect.
It is foreseeable that DGIWG WMS will reference metadata documents based on the
DGIWG metadata specification. It is foreseeable that
UKMOD WMS will reference metadata
documents based on the UK MOD Geospatial Metadata
Profile MGMP.
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Copyright © 2014 Open Geospatial Consortium.
FeatureList URL
General A server may use
a FeatureListURL element to point to a list of the features represented in a
Layer. FeatureListURL is not inherited by child layers.
DGIWG requires that If the GetCapabilities document identifies support
for FeatureListURL then the list of features that are in the particular layer shall be
resolvable through the provided URL. Additional clarification: “DGIWG might
want to define either a structure for the FeatureListURL or at least provide an
example” Supported as specified in the
OGC WMS 1.3 Standard.
DataURL General
A server may use DataURL to offer a link to the underlying data
represented by a particular layer. DGIWG requires that If the
GetCapabilities document identifies support for DataURL then the underlying data of the
particular layer shall be resolvable through the provided URL.
Supported as specified in the OGC WMS 1.3 Standard.
Layer General
A Layer may have zero or more of the following XML attributes:
queryable, cascaded, opaque, noSubsets, fixedWidth, fixedHeight.
All of these attributes are optional and default to 0. Each of these
attributes can be inherited or replaced by subsidiary layers
DGIWG profile requires that a DGIWG WMS server shall provide the XML
Attributes: queryable, cascaded, Opaque, noSubsets, fixedWidth and fixedHeight.
Queryable attribute must be provided however, a Layer
may have zero or more of the following XML
attributes: cascaded, opaque, noSubsets, fixedWidth,
fixedHeight. Layer
queryable DGIWG Web Map Service WMS
1.3 Profile: All layers publishing vector data and coverage data shall
be queryable. DGIWG Web Map Service WMS 1.3
Profile: All layers publishing vector data and coverage data shall be queryable.
Requires all services offering vector layers to be
queryable.
Copyright © 2014 Open Geospatial Consortium.
15 Layer
noSubsets Allows both subsettable and non-
subsettable layers. When set to a true value, noSubsets indicates that the
server is not able to make a map of a geographic area other than the layers
bounding box. The DGIWG Web Map Service WMS 1.3
Profile: All layers published by the service shall be subsettable and resizable - enables
the client to benefit from service-oriented data dissemination.
All layers published by the service shall be subsettable,
resizable and not defined as opaque.
Format General
Every server shall support the default textxml format defined in Annex A.
Support for other formats is optional. If the request specifies a format not
supported by the server, the server shall respond with the default
textxml format. DGIWG Requirement 3 states that A
DGIWG WMS server shall support textxml and texthtml as output formats for the
GetCapabilities and the GetFeatureInfo Operations
The default format for the response to a
GetCapabilities must be “textxml”. Other formats
may be present, but must include as a minimum
“textxml”.
16
Copyright © 2014 Open Geospatial Consortium.
Layer MinScaleD
enominator and
MaxScaleD enominator
The WMS service must be configured to serve requests that
range from at least 4x to at least 0.25x the native scales or
resolutions of the underlying datasets, and match commonly used
scales such as [15000 110k 125k 150k 1100k 1250k 1500k 11M
12M 14M 15M 110M]. A compliant service would serve
[VMap0 layers or 1M raster maps from 4M to 250k], [VMap1 layers or
250k raster maps from 1M to 50k], [VMap2 layers or 50k raster maps
from 250k to 10k], [5m imagery or elevation data from 1m pixel-
resolution to 20m pixel-resolution] A DGIWG WMS server shall provide scale
denominators for all layers it provides. A DGIWG WMS service should be configured
to serve requests that range from at least 4x to at least 0.25x the native scales or
resolutions of the underlying datasets. For layers that are providing
data which is presented at an appropriate range a
MinScaleDenominator andor a
MaxScaleDenominator should be provided for such
a layer. If both are present, the MinScaleDenominator
value shall be lower than the MaxScaleDenominator
value.
6.2 GetMap Operation
