Geocoding Standards
I began this page to document my research in the best ways to exchange small chunks of
geographic information. My key project at the beginning is to find a common format (or perhaps
two) for transferring point locations, areas, track logs, and POI information among different
mapping applications, primarially for use in emergency mapping applications, such as APRS and
Google Earth.
My key requirements are:
- As compact a format as possible, for transmission efficiency
- Inclusion of the map datum
- Support for decimal degrees
- Support for altitude
- Support for circles and polygons
- Support for free-form and structured annotation, so I can provide a label for the point or area, as
well as information such as how many people a shelter can hold, if it has radios or antennas, if it has
showers, etc. Some key information should be structured such that it can trigger the appearance of
standard symbols in a pop-up attribute box, balloon, etc.
The existing standard formats I am evaluating are:
- GPX
- Cons: No polygonal areas and no circles.
- KML
- Cons: no circles.
- GML
- Pros: Requires specification of the datum (coordinate reference system)
- Cons: no circles.
- GeoRSS
- Pros: GeoRSS GML supports specification of the datum
- Simple Features
- Cons: no circles.
- shapefiles
- GeoJSON
Why circles?
Why not? A circle is the fourth most basic geometric construction, after points, lines, and polygons.
Its absence from the geographic modeling systems is a fundamental flaw.
I personally need circles in order to map:
- The amateur radio 70 cm band exclusions of 100 miles around the Cape Cod PAVE PAWS station and
140 miles around the Beale Air Force Base PAVE PAWS station.
- The distance to the horizon for a given height radio antenna.
- A warning or search radius; I'd like to visualize a 2-mile circle around my current location, and have
a map display that radius and ally my friends (and enemies!) and other search queries within that circle.
- The circle covered by weather radar stations.
- A circle indicating approximate Wi-Fi coverage around hotspots.
- A circle indicating how far I can see from a landmark (Coit Tower, the Space Needle, etc.)
