HSLayers (Help Service + OpenLayers) combines capabilities of ExtJS and OpenLayers and several helping scripts to establish truly Web GIS applications. Development started in 2007. In 2009, after 2 years of development, it was released under conditions of GNU General Public License 3.
OpenLayers is a JavaScript toolkit for creating of mapping applications in the web browsers. OpenLayers is more powerful than Google Maps toolkit. It has abilities for showing maps based on various raster and vector formats. It has connectors to many standards and quasi-standards such as MapServer, OGC Web Mapping Service, ArcIMS, simple Image layer, GML, GeoRSS, KML, Text and others and Google, Yahoo and VirtualEarth for commercial data providers. The user – creator of mapping application – does not need to take care about differences between various web browsers and their JavaScript implementation or between various data formats.
ExtJS is a multi-browser JavaScript library for building of rich internet applications. It consists from customizable User Interface widgets, ready to be used by designers of Graphical User Interface, similar to desktop widgets, which among others are text field and text area input controls, date fields with a pop-up date-picker, numeric fields, list box, radio and checkbox buttons, wysiwyg html editor, text grids, suitable for spreadsheets, trees, tab panels, toolbars, menus and sliders. ExtJS was originally built as an add-on library extension of Yahoo UI, but now it is the standalone project.
HSLayers features are coming up from OpenLayers and therefore their characteristics are as follows:
-
Portrayal of various types of data:
- Raster: OGC WMS(-T), Image (PNG, JPEG, GIF), …
- Vector: OGC WFS(-T), GML, GeoRSS, KML, GPX, GeoJSON, …
- Data sources from commercial servers: Google Maps, Virtual Earth, Yahoo Maps, …
- The user interface (use control) adheres to current conventions in web map portals.
- Information about queried objects in text bubbles.
HSLayers additional functions:
- Dynamic adding of OGC (Open Geospatial Consortium) services into map - clients for WMS and WFS
- Portrayal of independent data sources on the client side. Map composition is composed on the basis of requests to various servers. It is thus not necessary to install a map server.
- Saving of map composition according to WMC (Web Map Context) OGC specification on user computer for repeated future use or for sharing between users.
- Extension of compute functions based on WPS (Web Processing Service) OGC service - according to user needs
- Multilingual environment
- Map requests to various types of data stored on various servers, with automatic processing of results
- Work with micro-formats
- Search on the map
- Connection of the application with catalogue client (OGC CSW) in the geoportal, which enables display of the searched service from catalogue directly on the map.
- Edit function - snapping to chosen layers
- Possibilities for advanced configuration of user requests
- Advanced measuring of length and surfaces
- Print of map compositions - possibility of large print outs (up to A0 format), user configuration of print settings
Tourism portal Posazavi: A map is a part of the web site.
Light version of HSLayers is used to build into web sites. Its functionality might be limited in comparison with the portal version, especially in user comfort (the light version does not use ExtJS library as the user interface). Regardless, some components using ExtJS library can be used in the light version according to user needs.
Geoportal
The Geoportal version is a heavy version of the web based map viewer HSLayers. Beside a map with the necessary control features (layer management, length measurements, map inquiries throughout all displayed layers, print, etc.), catalogue client, MapMan (tool for creation map compositions, supplied by Help Forest), authentification module, metadata editor MIcKA, other features can be used. All components are interconnected and communicate with each other.