Duncan Garratt
Hi Simon
What is not on my website, and perhaps should be is that I specialise in writing standalone GIS mapping systems, for the Web, Windows and Linux. The reason for using Virtual Earth or Google Maps is the cost of map data; many of the alternatives are simply beyond reach of potential customers (OS Mater Map, Street level data, etc), unless you are talking about tracking systems (Navteq).
Having said that for specialised GIS systems I do use a number of third party mapping engines that handle the common GIS file formats. Additionally I do have my own mapping engine that handles raster data, which was used for the web before Google Maps, and Virtual Earth were invented.
Depending on map data volumes, concurrent users/standalone system, system architecture etc, will dictate what are the best libraries to use. ESRI is one route, but there are a number of others, which often work out considerably cheaper.
The big advantage of this route is the saving in software royalties, where there are large volume sales, or large numbers of users. (Please note that map data royalties are still payable)
Map data storage requirements Navteq UK Street level data
249 MB ESRI Shape File Format
9.47 GB Geo Tiff
What you appear to be talking about is hosting the map data locally on the machine, or on a local server. This should not be problem depending on the spec of the machine, volume of map data, and library used. Equally handling the NEMA input from a GPS is a straightforward matter.
Duncan Garratt
http://www.gis-logic.co.uk