To use the
coneskymatch command you need the
service URL (also known as the base URL
or access URL) of a cone search, SIA or SSA service to use.
If you know one of these representing a service that you wish to use,
you can use it directly.
If you don't, you will need to find the URL from somewhere. It is the job of the Virtual Observatory Registry to keep a record of where you can find various astronomical services, so this is where you should look.
There are various ways you can interrogate the registry; the easiest is probably to use a graphical registry search tool. One such tool is AstroGrid's VOExplorer, which allows you to perform sophisticated searches for cone search, SIA or SSA services. Another option is to use TOPCAT; the Cone Search, SIA and SSA load dialogues allow you to search the registry for these services prior to performing a query; you can just use the registry part and cut'n'paste the URL which is shown.
Other registry querying tools are available, including STILTS's
command. See that section of the manual for details, but for
instance to locate registered Cone Search services which have
something to do with SDSS data, you could execute the following:
stilts regquery query="capability/@standardID = 'ivo://ivoa.net/std/ConeSearch' and title like '%SDSS%'" \ ocmd="keepcols 'shortName AccessUrl'" \ ofmt=asciiWriting just
query="capability/@standardID = 'ivo://ivoa.net/std/ConeSearch'"with no further qualification would give you all registered cone search services.