Links and Resources

1. Spatial Reference Systems (SRS)

Geospatial data are stored and displayed in different coordinate systems, either as geographic (latitude / longitude) or projected coordinates. Suitable coordinate systems depend on purpose, size and location of study areas, and communication context.

Spatial reference systems are defined and available through catalogs like >http://spatialreference.org. For higher accuracy, these definitions not only include a type and parameterisation of a (map) projection, but are also based on a specified geodetic datum.

To refer to unique SRS, most software environments use EPSG coding, enabling a code like 2060 to identify UTM zone 40 coordinates based on the European Datum (ED).

2. Globe View

Navigate >this globe and recall, how the lat/long reference system is organized!

3. Maps and Coordinates

Any planar ('flattened') map like the one below requires a projection. When you open this map in a separate window ('View larger map'), then right click on any location and select 'What's here?' the geographical coordinates of this location are displayed. They are well suited as unique identifiers for a location, but not for planar mapping and measurements - try right click and 'Measure distance'!

4. Apply Coordinate Systems

>This map per default displays geographical coordinates for each position in the lower left corner. There you can select alternative projections (UTM and Lambert, both primarily valid in this region, i.e. Austria - do not use this in different global regions). After selecting a projection, select the positioning tool at the left side of the location widget and place a marker at some location of interest.

Compare the coordinate values for identical locations!

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5. Coordinate Transformation Service

The OGC has developed and is offering a specification for an online transformation service > http://www.opengeospatial.org/standards/ct (WCTS): 'The OpenGIS® Coordinate Transformation Service Standard (CT) provides a standard way for software to specify and access coordinate transformation services for use on specified spatial data.'

In practice, this makes it possible to dynamically align and overlay geospatial data from sources in different reference systems.

Check out a sample implementation of WCTS from Italy >http://www.pcn.minambiente.it/mattm/en/conversione-coordinate-sincrono!

Get eg the lat long coordinates of Rome from the map in a section above, and convert into UTM (ED50 / UTM zona 33N).

6. From Placenames to Locations

Few people use coordinates to refer to locations in their daily lives. Places have names, and for location and display of places names need to be translated into coordinates. 

This is done through Gazetteer services - "Service that provides access to a directory of instances of a class or classes of real-world phenomena containing some information regarding position" (definition by INSPIRE).

Practically speaking, we type a placename, resolve potential ambiguities (select from multiple places with identical or similar names) and get location coordinates. One popular example for a gazetteer is the >GeoNames service.

This functionality is frequently integrated into online apps, like the >Hexagon Geospatial Portal - try this out!

7. Urban Places - Addresses

The most frequently used georeference in personal communication is street addresses, for use in display, navigation etc these need to be translated into coordinates as well - we refer to this process as 'geocoding'.

GIS and mapping systems include geocoding functionality, eg when looking for >'Kapitelgasse 2 in Salzburg, Austria', the main admin building of Salzburg University.

Experiment with geocoding in Google (link above) and ArcGIS Online (map below), and consider the importance of this function in geospatial user interfaces like SDI portals!