Transcript
CRS and SVG
Satoru Takagi , SVGWG
I am a engineer who have been developing Geographic Information Systems and Web Mapping Systems which used SVG for about fifteen years.
Self-introduction
And I am taking charge of the standardization in SVGWG mainly concerning Mapping.
Moreover, I was involved also with de-jure standardization of GML in Japan, and a development of the RDF vocabulary for geospatial information.
http://svg2.mbsrv.net/devinfo/devkddi/lvl0.1/
My interest is fusion of graphics on web and geographic information.
In particular, it is a map contents as a graphics.
It is because a lot of map contents are on the web.
This document will search for the gap between such a graphics and geographic information.
The aim of this slide
Graphics A Graphics B
User Coordinate System A User Coordinate System B
Unrelated
Graphic Contents
On mere graphics contents, each contents are usually unrelated. Therefore, these coordinate systems are also individual and unrelated.In SVG, such coordinate systems are called User Coordinate System.
Coordinate Reference System : EPSG:3857
Geographic Information System A
Geographic Information System B
Geographic Information System C
Geographic Information Systems
for instance
Geographic information systems has CRS. Since common well known CRS is shared by multiple GIS, we can make these cooperate, such as layering.
(CRS)
Coordinate Reference System : EPSG:3857
Geographic Information Systems
for instance
Even if different CRS are used among GIS, we can still cooperate by CRS transformation.
EPSG:3995
EPSG:4326
EPSG:326xx
CRSTransformation
Unrelated
User Coordinate System A
User Coordinate System B
User Coordinate System B
Map content A
Map content B
Map content C
Map Contents
On the other hand, there is no concept of CRS on mere map contents. Since it is a kind of graphics contents eventually.
Therefore, we cannot make these cooperate.
The map contents by SVG are also in the same situation basically.
Geographic Coordinate Systems Section on SVG1.1
http://www.w3.org/TR/SVG/coords.html#GeographicCoordinates
Meanwhile, there is specification concerning CRS in SVG1.1.It is the specification for embedding geospatial coordinate system information as metadata into map contents.
Accordingly, it allows to regard map contents also as geographic information. It could be called one of the styles of Spatial Data on the Web.
User Coordinate System A
User Coordinate System B
User Coordinate System C
Map content A
Map content B
Map content C
svg:transform
svg:transform
svg:transform
Coordinate Reference System : EPSG:3857
Geographic coordinate SystemsMetadata on SVG1.1
for instance
That metadata is constituted by CRS of the source geographic information used on the map generation process, and its coordinate transformation factor to User Coordinate System of the map content.
<?xml version="1.0"?><svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="100" height="100" viewBox="0 0 1000 1000">
<metadata> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:crs="http://www.ogc.org/crs" xmlns:svg="http://www.w3.org/2000/svg"> <rdf:Description rdf:about=""> <!-- The Coordinate Reference System is described through a URI. --> <crs:CoordinateReferenceSystem svg:transform="rotate(-90)" rdf:resource="urn:ogc:def:crs:EPSG::3857 "/> </rdf:Description> </rdf:RDF> </metadata>
<!-- The actual map content --></svg>
ExampleMap_content A.svg
ISSUE
• It is too flexible and complicated by RDF/XML.• Browsers provides no functions which used it,
since it is mere metadata.• It is still future that SVG is widely used for map
contents.
Nobody is using it.
That specification will be removed in SVG2. And it is under re-examination. The person in charge is me.
https://svgwg.org/svg2-draft/
https://svgwg.org/specs/transform/
Our Directivity of re-examination
In order to promote SVG map contents with CRS,• Markup should be simpler. • Browsers should have certain convenient native
functions using CRS.
In order to promote Browser implementations,• The concept of CRS should be generalized. • Such functions using CRS should be general-purpose
not only for spatial information and mapping.Because standardization of multiuse functions is welcomed for web browsers.
http://www.w3.org/Graphics/SVG/2014/new-charterSee also SVGWG’s charter
Generalized CRS concept?My thought:
Generalized CRS is the concept of a certain coordinate system which multiple contents or systems share. There may be a variety of shared coordinate systems. Therefore, it intends that it is declared on a content or a system so that it may be known by the others what coordinate system is used.
The coordinate transformation among different CRS is a extended concept according to a case such as geo-graphical.
Is it acceptable for geo guys?Should another name for this concept be attached?
General-purpose functions by CRS
Layering
Gemini2DIllustration
Caption Layer
Marker Layer
Sketch Layer
CRS = “Gemini2DIllustration”
CRS = “Gemini2DIllustration”
CRS = “Gemini2DIllustration”
CRS = “Gemini2DIllustration”
Layering shares a common coordinate system among layers.
CRS = “ZoomableWireFrameIllustration”
CRS = “ZoomableWireFrameIllustration”
CRS = “ZoomableWireFrameIllustration”
CRS = “ZoomableWireFrameIllustration”
Hi Res. Content
Low Res. Content
Medium Res. Content
The level of detail function shares a common coordinate system among contents of each resolution.
Level of Detail
Tiling (High resolution Graphics)
See also: Microsoft’s Zoomable High-resolution Photoshttp://www.microsoft.com/web/solutions/zoomit.aspx
Tile1-1 Tile2-1 Tile3-1 Tile4-1
Tile1-2 Tile2-2 Tile3-2 Tile4-2
Tile1-3 Tile2-3 Tile3-3 Tile4-3
Tile1-4 Tile2-4 Tile3-4 Tile4-4
On tiling, each tile graphics share a common coordinate system.
These functions are important also for GIS and Web Mapping.
Are there any other general-purpose functions which used CRS?
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