Representation in the “Places” tree in the Google Earth client
Copyright © 2014 Open Geospatial Consortium
21
west-75.0west LatLonAltBox
Lod minLodPixels512minLodPixels
maxLodPixels-1maxLodPixels Lod
Region Link
hrefhttp:services.interactive-instruments.deows7- kmlkml2wfskml.phphref
viewRefreshModeonRegionviewRefreshMode viewFormatBBOX=[bboxWest],[bboxSouth],[bboxEast],[bboxNorth]amp;LOOKAT=[look
atLon],[lookatLat],[lookatRange],[lookatTilt],[lookatHeading]amp;CAMERA=[camer aLon],[cameraLat],[cameraAlt]amp;LOOKATTERR=[lookatTerrainLon],[lookatTerrainL
at],[lookatTerrainAlt]amp;VIEW=[horizFov],[vertFov],[horizPixels],[vertPixels] ,[terrainEnabled]viewFormat
httpQueryCLIENTINFO=[clientVersion];[kmlVersion];[clientName];[language]amp; TYPENAME=tds:PowerStationGeosurface,tds:PowerStationGeopointhttpQuery
Link NetworkLink
Folder Folder
nameGeneral Structuresname visibility1visibility
open0open descriptionBuildings and their components, non-building structures
and man-made barriers for example: walls and fences. [desc] They are geographically widespread and may be located in rural, urban andor industrial
settings.description Snippet maxLines=0
NetworkLink nameTilesname
visibility1visibility open0open
refreshVisibility0refreshVisibility flyToView0flyToView
Region LatLonAltBox
north20.0north south17.0south
east-65.0east west-75.0west
LatLonAltBox Lod
minLodPixels512minLodPixels maxLodPixels-1maxLodPixels
Lod Region
Link hrefhttp:services.interactive-instruments.deows7-
kmlkml2wfskml.phphref viewRefreshModeonRegionviewRefreshMode
viewFormatBBOX=[bboxWest],[bboxSouth],[bboxEast],[bboxNorth]amp;LOOKAT=[look atLon],[lookatLat],[lookatRange],[lookatTilt],[lookatHeading]amp;CAMERA=[camer
aLon],[cameraLat],[cameraAlt]amp;LOOKATTERR=[lookatTerrainLon],[lookatTerrainL at],[lookatTerrainAlt]amp;VIEW=[horizFov],[vertFov],[horizPixels],[vertPixels]
,[terrainEnabled]viewFormat httpQueryCLIENTINFO=[clientVersion];[kmlVersion];[clientName];[language]amp;
TYPENAME=tds:BuildingGeopoint,tds:BuildingGeosurfacehttpQuery Link
22
Copyright © 2014 Open Geospatial Consortium
NetworkLink Folder
Folder nameBurial Sitesname
visibility1visibility open0open
descriptionA structure within which a corpse is entombed or an area of ground in which the dead are buried. Also includes the buildings and
services used in the preparation and disposal of the dead and related activities. [desc] It may be either a site where remains of ancient
civilizations have been discovered or a modern day facility.description Snippet maxLines=0
NetworkLink nameTilesname
visibility1visibility open0open
refreshVisibility0refreshVisibility flyToView0flyToView
Region LatLonAltBox
north20.0north south17.0south
east-65.0east west-75.0west
LatLonAltBox Lod
minLodPixels512minLodPixels maxLodPixels-1maxLodPixels
Lod Region
Link hrefhttp:services.interactive-instruments.deows7-
kmlkml2wfskml.phphref viewRefreshModeonRegionviewRefreshMode
viewFormatBBOX=[bboxWest],[bboxSouth],[bboxEast],[bboxNorth]amp;LOOKAT=[look atLon],[lookatLat],[lookatRange],[lookatTilt],[lookatHeading]amp;CAMERA=[camer
aLon],[cameraLat],[cameraAlt]amp;LOOKATTERR=[lookatTerrainLon],[lookatTerrainL at],[lookatTerrainAlt]amp;VIEW=[horizFov],[vertFov],[horizPixels],[vertPixels]
,[terrainEnabled]viewFormat httpQueryCLIENTINFO=[clientVersion];[kmlVersion];[clientName];[language]amp;
TYPENAME=tds:CemeteryGeopoint,tds:CemeteryGeosurfacehttpQuery Link
NetworkLink Folder
Folder
... Document
kml
However, the results have not been satisfactory. With about 30 leaf packages this results in many parallel connections to the WFS per region. Considering that in a single view
several regions may be visible this quickly turns into several hundreds of parallel WFS requests for a single client. As a result this approach does not scale very well – or at least
it requires a high-performance server architecture.
There are several measures that could be made to considered to make this work in an operational context, too:
Copyright © 2014 Open Geospatial Consortium
23 - Higher aggregation. Instead of using the leaf packages, maybe just use the first
package layer to reduce the number of KML folders ie. parallel requests - Improved implementation. For the testing purposes we converted the encoding rule
into XSLT scripts that convert a GML file from the WFS to its associated KML file. Since the model is quite big this results in a large XSLT script upto 2MB which is
invoked in every request. While further improvements to the XSLT execution are possible, for a real fit-for-purpose implementation the KML should be encoded
directly by the WFS instead of the detour via GML.
- For data that does not change too often, the KML for a tileregion could be stored as a KMZ file so that only a file access is necessary. These KMZ files could be derived
directly from the WFS as a cache and placed in the file system by a periodic process, if needed.
6 Constraints expressed using Schematron