The Kinematic GPS (KGPS) data provide accurate high-resolution locational data of approximately 6400 km of roads in Great Britain using circular and/or linear transect data collected during two fieldwork campaigns (details below) carried out by the Landmap project team in order to validate the various Landmap image and elevation products. When processed, this data yields accurate 3-D coordinates that can be used for quality assessment purposes. Kinematic GPS is a technique used to enhance the precision of standard GPS, using a reference receiver of known location, such as a main road, to make corrections to the standard GPS-determined location yielding centimetre-level accuracy.

The Joint Information Systems Committee (JISC) funded Landmap service which ran from 2001 to July 2014 collected and hosted a large amount of earth observation data for the majority of the UK, part of which was buildings data. After removal of JISC funding in 2013, the Landmap service is no longer operational, with the data now held at the NEODC.

Campaign 1

The first campaign, carried out in September 1999, required the kinematic GPS profiles for a number of pre-defined circular routes. This suited a 'Real-time Kinematic' (RTK-GPS) survey technique in which both GPS code pseudorange and carrier-phase measurements are recorded. This method is capable of yielding sub-decimetre accuracy over short baselines, generally less than 50 km.

The observing schedule was such that the reference receiver was established at a location deemed to be the centroid of the day's route so that the baseline distances from the 'local' reference receiver to mobile receiver would be kept to a minimum preventing the accumulation of distance-dependent errors. The mobile receiver would then be driven along the predefined route recording satellite observations at a rate of 5 Hz. Once the route was completed, the local reference station team was picked up and the entire team prepared to observe the next scheduled loop.

The mobile team covered almost 4,000 miles during the 14 days of the first campaign with the predefined circular routes representing some 2,800 miles (4,506km) of that total.

Campaign 2

The second campaign which took place during May and June of 2000 was geared to a different set of objectives and therefore had an observing schedule different to that of the first campaign. There was a requirement to observe some long GPS profiles that would essentially span a number of satellite-pass strips / several stereo-pair strips permitting some checking of the strip matching procedures using orthorectification techniques.

The establishment of a 'local' reference receiver station alongside each section of these proposed transects would have been too demanding in both time and logistics so an alternative processing approach was decided upon. The observing procedure was identical to that of the first campaign with the exception that the 'local' reference receiver remained in the same location for the duration of the campaign. A high-precision geodetic GPS receiver was established at a point of known co-ordinates at University College London where it collected GPS observations for the 9 days of this second campaign. The mobile receiver was driven along the required profiles recording data at a rate of 5Hz.

The routes followed for this second campaign contained a number of features as requested by the SPOT processing team that would aid them in their orthorectification tasks. One particular request was that a number of crossovers should be performed at major junctions whereby a mile or two of additional observations were taken on the feeder roads for the junction in question. Such manoeuvres provide the processing / imaging team with a greater number of features to identity and refer to as part of their orthorectification quality assessment routines. The nature of the road network in some areas meant that several long stretches of road were retraced or intersected which allowed some error checking.