Combining geodata using Web Map Server ISO/TC 211 Seminar

Transkript

1 Combining using Web Map Server ISO/TC 211 Seminar Anders Skog, SIS/TK

2 Content Maps in Swedish national strategy Combining maps: the problem and how to solve it SIS/TK 570 Web cartography

3 Advanced cooperation for open and usable via services Drawn up by Lantmäteriet in consultation with the Swedish Geodata Council Vision: Sweden has a highly effective infrastructure for. This means that it is easy to search for and find and services. Geodata from different sources can be accessed via services, and can easily be combined. strategy_ pdf

4 National basic data Innovation and growth Digitisation of public administration A more effective social planning process Climate adaptation and environmental threats Defence and civil contingencies

5 Criteria for national basic datasets shall be requested on national and local level shall be based on existing initiatives shall be maintained and distributed in an effective way shall be easy to use shall be easy to access shall be up to date shall be provided also as raw data shall be provided by a common national map service

6 From Swedish Geodata Council action plan for 2017 Draft a vision, requirements, a plan, and a prototype for development and maintenance of a common national map service (API) for the national basic datasets

7 Common national map service requirements for a solution Basic requirement: Organizations developing map applications must trust the solution and dare to phase out local storage of data and local development of such map services. Requirements to be drafted: abilities for combination and integration of abilities for selection of features to be viewed abilities for controlling portrayal of features abilities for zooming, panning, measuring, printing standards to be used accessability, stability, level of service

8 Web map service not just a server! Server to call Service specification Development support Test environment Certification

9 producers providing and services s e r v i c e Our model with actors developers ing web map and application users of web map and application wants to offer functionality, facilitate use, maintain the service, produce the service, but it must not be too expensive, risky, wants to combine data sources, cartography, filter data, develop applications, but it must not be too complicated, slow, expensive, knowledge demanding, unreliable, wants to search, zoom, pan, select, measure, read, understand,

10 Our model is based on WMS Web browser Success factors Accepted standard Technical abilities Many software suppliers Simple to use for applications web map webbkarta Application with WMS client map layer WMS WMS WMS

11 Service based data exchange + combinable sources + challanges (simplified example) intension actual web map webbkarta web map webbkarta map layer map layer WMS WMS WMS What can be done to make the producers provide a service that the application developer can use to make the maps that the end user needs?

12 The problem combinations that make it harder to read and understand. How to get map layers that you can combine? Overlapping areas covering each other Similar symbols with different meanings Unwanted combinations of colours Overlapping grids giving strange results Unwanted results when zooming webbkarta webbkarta

13 How to get map layers that you can combine? Frequent solution: Skip the WMS! Store data locally! produce produce Download services batch download batch download consume consume Using tools for creating cartography for remote or local data. tools application use User Violates the strategy: dare to phase out local storage of data

14 How to get map layers that you can combine? Obvious solution: Use WMS but ask the service providers! produce produce W M S W M S consume consume application use The application developer affects the service by makeing requests for the required cartography Tailored services are not really services!

15 How to get map layers that you can combine? Good solution: WMS with choice of alternative cartography! produce W M S consume select 2 produce W M S select consume 2 application use Web map services providing alternative cartography for each feature type. Select the most suitable. User SIS/TK 570 national technical report with guidelines for web map services where the service provider defines the cartography. Guidelines: provide layers with limited content provide cartographical alternatives provide complete documentation

16 How to get map layers that you can combine? Flexible solution: WMS with application control of cartography! produce W M S consume SLD+SE produce W M S consume SLD+SE application use Web map services providing an interface for controlling cartography. Design the cartography. User SIS/TK 570 national technical report with guidelines for web map services where the application developer defines the cartography. Guidelines: support SLD enabled WMS with user styles provide documentation an examples for the developer eliminate risks

17 How to get map layers that you can combine? Feature service solution: Skip the WMS! Use WFS to get data! produce W F S consume produce W F S consume tools application use Download services Using tools for creating cartography for remote data. User Next (?) SIS/TK 570 national technical report with guidelines Guidelines: provide service that supports map application development provide documentation that supports map application developer

18 How to get map layers that you can combine? Actual solution: Mixing F t p A t o m W F S W C S W M S SLD+SE use plus new technology and new tools.

19 Solution trade-off ready-made cartography raw data simple! hard to read! hard to understand! ugly! complicated! flexible! understandable! optimal! fancy! reusable standardised easy to use platform neutral affordable encouraging reliable

20 Model of actors extended version s e r v i c e Government wants use provide services use services

21 Web map solutions return of investment Solutions Downloaded data + develop a web map application WMS + only default cartography + develop a web map application WMS + alternative cartography + develop a web map application WMS + smart SLD support + develop a web map application WFS + develop a web map application Money Development cost for service provider Development cost for applications Maintenace costs Savings for society

22 SLD enabled WMS web map service with style interface (SLD = Styled Layer Descriptor) WMS Metadata from sever: GetCapabilities layers & styles DescribeLayer(layers) feature types DescribeFeatureType(feature types) GML schema t o o l XML! Help! SLD <UserStyle> <FeatureTypeStyle> rules (SE) WMS GetMap(SLD) response with image a p p l i c a t i o n use

23 Smart SLD support user friendly metadata and examples that lower the threshold for developers WMS Metadata from sever: GetCapabilities SLD prototype layers & styles DescribeLayer+layers Good example providing WFSs & feature types DescribeFeatureType+objekttyper all information the GMLschema application developer needs SLD <UserStyle> <FeatureTypeStyle> rules (SE) WMS GetMap(SLD) response with image ev de ri kt ot yr g a p p l i c a t i o n use

24 Riktlinjer 1 I SLD-prototypen bör applikationsutvecklaren kunna hitta all den information som behövs för att använda möjligheterna. SLD-prototypen bör framför allt ta upp namn på skikt, variabler och värden. SLD-prototypen bör vara en syntaktiskt korrekt SLD-fil. SLD-prototypen bör, direkt eller indirekt, ange alla symboliska namn som kan behövas och deras innebörd. SLD-prototypen bör med exempel visa principen för hur symboliska namn anges med <Name>, <PropertyName> och <Literal>. SLD-prototypen bör visa var <Title> och <Abstract> kan och bör införas. SLD-prototypen bör med XML-kommentarer ange förklaringar, instruktioner och annan dokumentation som riktar sig till applikationsutvecklaren. SLD-prototypen bör beskriva hur texter anges som attributvärden, hur de är kodade och hur de används i jämförelser. SLD-prototypen bör använda sig av den teckenkodning som servern förväntar sig. Den teckenkodning som anges i SLD-prototypen ska stämma med faktiska kodningen. SLD-prototypen bör använda UTF-8 för teckenkodning

25 Riktlinjer 2 SLD-prototypen bör beskriva regler för stavning och kodning av symboliska namn och värden som finns i externa källor. SLD-prototypen bör beskriva hur numeriska värden och datum anges och är kodade och hur de används i beräkningar och jämförelser. SLD-prototypen bör beskriva kodning och utseende för av servern kända symboler. SLD-prototypen bör ange exempel på <FeatureTypeStyle>. <FeatureTypeStyle> bör innehålla minst en <Rule> med enkelt exempel på <Filter>, skalintervall och <Symbolizer>. För <Filter> bör framgå hur relevanta attribut används. Det bör framgå hur <TextSymbolizer> används för textattribut. Det bör finnas exempel på <Filter> som gör sammansatta urval, om dessa är särskilt viktiga

26 Riktlinjer 3 Utgångspunkten för en kodad stilmall bör vara en SLD-prototyp. Taggen <Name> bör endast ange symboliska namn. Taggen <Title> bör endast ange namn som ska kunna förstås av användare. Taggen <Abstract> bör ange beskrivningar som ska kunna förstås av användare. XML-kommentarer bör ange instruktioner och förklaringar som riktar sig till applikationsutvecklare. Om GetLegendGraphic stöds bör det framgå av SLD-prototypen. Om GetLegendGraphic stöds bör SLD-prototypen innehålla de <Name> som behövs. Om svaret är XML-kodat bör symboliska namn (<Name>) användas. Applikationen bör översätta symboliska namn till mer beskrivande namn. Om svaret är html-kodat eller okodat bör beskrivande benämningar användas. En applikation bör indikera att kartskikt ännu inte har levererats. En applikation bör indikera att kartskikt inte kan levereras. En applikation bör indikera att kartskikt inte visas för att de är utanför skalområdet

27 XML! Help! SLD prototype XML editor style examples + user needs good cartography

28 SIS/TK 570 Web cartography Lantmäteriet Swedish Transport Administration Swedish Maritime Administration Swedish Armed Forces Geological Survey of Sweden County council of Stockholm City of Malmö Experts Technical report later this year: Screen based maps Web distributed maps Services Standards International trends Guidelines for SDI Guidelines for service providers Guidelines for application development Guidelines for map interactivity Guidelines for cartography SIS-TR 30, Geographic information Web cartography Guidelines for combinable web map services In Swedish. No plans for English translation. Yet. Tack!