In June 2006 the NERC-funded Network for Calibration and Validation of EO data (NCAVEO) organised a cal-val field experiment in Chilbolton, north Hampshire involving 48 scientists from 20 organisations (click for list). The aim was to undertake a validation exercise based on the protocols and methods developed by the Validation of Land European Remote Sensing Instruments (VALERI) project, but modified as necessary for UK conditions. The experiment is a scoping exercise for the establishment of one or more VALERI sites in the UK as well as an opportunity to learn and share best practice amongst NCAVEO partners and the wider community. The initial plan was to base the experiment at the Barton Bendish test site in East Anglia, but the absence of on-site instrumentation coupled with uncertainty about access to this site and its distance from the main research groups led to a search for other suitable sites. The one chosen was centred on the Services and Technology Facilities Council Chilbolton Facility for Atmospheric and Radio Research (CFARR), approximately 45 km north of Southampton (Figure 1). CFARR comprises a number of state-of-the-art instruments for measuring atmospheric properties, including the 25 metre diameter Chilbolton dish, a 3 GHz doppler-polarisation radar, 1275 MHz clear air radar and a UV vertical sounding LiDAR In addition, the site has a full suite of continuously operating meteorological instruments. Datasets collected include Digi HRG data, remotely sensed data from 2 aircrafts, ground spectral data , atmospheric data, biophysical data, and fluvial geomorphological data.

A Delta-T BF2 Sunshine Sensor was used to measure the total and diffuse sky irradiance every minute from 10:30 to 13:00 hours on the 17th June 2006, as part of the Network for Calibration and Validation of EO data 2006 Field Campaign. 150 readings were produced in total. The direct energy of the sun on the instrument is calculated from the differences between the total energy and diffuse component recorded simultaneously.

This dataset compromises data collected by the Compact High Resolution Imaging Spectrometer (CHRIS) over Chilbolton, 17th June 2006, as part of the Network for Calibration and Validation of EO data (NCAVEO) 2006 Field Campaign. The data were collected in Mode 1, which has 34 metre pixel size and 62 spectral bands between 411 nm and 997 nm, giving a ground resolution of 34 metres. Surrey Satellite Technology Ltd is the owner of all data directly resulting from in-flight operation of the CHRIS instrument flown on- board the ESA PROBA spacecraft. All publications on the CHRIS instrument or data obtained from the CHRIS development and/or operation should therefore make explicit reference to Surrey Satellite Technology Ltd, the CHRIS instrument and the ESA PROBA mission. The L3b Directory contains data created by Ted Milton from the L1b, after having been destriped and registered to the OS grid. For more information on the structure and format of the data please see the associated metadata PDF for the dataset in linked documentation.

This dataset compromises eight flight lines which were acquired on 17th June 2006 using an Itres Instruments Compact Airborne Spectrographic Imager (CASI-3) as part of the Network for Calibration and Validation of Earth Observation data (NCAVEO) 2006 Field Campaign. The instrument was onboard a Cessna 404 aircraft operated by the UK Environment Agency (EA) and was operated in hyperspectral mode, with 32 spectral bands and a nominal ground resolution of 1m. The Environment Agency identified a possible spectral shift problem in the CASI-3 instrument during June 2006. The problem was corrected but it is still unknown how much the spectral shift occurred during data collection for NCAVEO. The document ‘CASI3 Wavelength correction for NCAVEO.pdf’ in further documentation provides further details. EasGeo software is also stored in the EasGeo folder in the directory as easgeo.sav, as well as documentation with further details on the data.

LiDAR data was collected by the UK Environment Agency on 17th June 2006 as part of the Network for Calibration and Validation of EO data (NCAVEO) 2006 Field Campaign. The data was collected from a Cessna 404 aircraft carrying an Optech 3100 LiDAR. The sensor was integrated with the on-board navigation system to provide accurate geometric correction through post-processing. The LiDAR was operated at 33 kHz to give a nominal pulse spacing around 1-2 m, and intensity plus first and last pulse returns were recorded. For further information please see the LiDAR survey report in linked documentation and the dataset's metadata document.

This dataset compromises measurements of the angular distribution of spectral sky radiance (400-1000nm), collected as part of the Network for Calibration and Validation of Earth Observation (NCAVEO) 2006 Field Campaign. Measurements were taken at frequent intervals on the 17th June 2006 using a new instrument designed by Andrew McGonigle. The instrument is based on a temperature-stabilised miniature spectroradiometer interfaced to a telescope that can be programmed to make zenithal scans of sky irradiance. Azimuthal motion of the whole instrument was provided by manual adjustment. A sampling interval of 18° in zenith and 30° in azimuth was used. All data were collected when the spectrometer was thermally stabilised to the same temperature (approximately 7.5°C). Each sample of the sky irradiance distribution comprised two scans: one of the whole sky, and then a second low-gain scan shortly afterwards, concentrating just on the region around the Sun. Scans were repeated twice, with different integration times to allow for the extreme differences in brightness of the Sun and the sky. For further information and details on the structure of the files see the dataset's metadata PDF in linked documentation.

The Network for Calibration and Validation of EO data (NCAVEO) ground data collection programme included a series of transects on the River Test at Chilbolton Cow Common, an area of semi-natural wet grassland. The river survey was carried out on the 16th June between 11:15 and 13:15 at site Chilbolton 1 and 15:30-17:00 at Chilbolton 2, the day before the ‘golden day’ on which the airborne data were collected by the Environment Agency / Natural Environment Research Council (NERC). The sampling strategy used was based on the desire to capture; (1) data over the range of water depths, (2) a dense and extensive sample of data to allow for bathymetric modelling of the river regions and (3) data over a broad range of substrate types to represent all varieties within the study region (e.g. from marginal vegetation to silts and to gravels). The variables recorded included: Easting; Northing; Water depth (cm); Depth to bed (cm); Surface velocity (m/s); Dominant substrate. Surface velocity was measured using a Valeport uni-directional electro-magnetic current meter (Valeport Ltd.). For more information on the collection and processing of the data please see the dataset's metadata document, in linked documentation. A video of David Spear describing the survey is available also included in the directory.

The DMC constellation of small satellites provided several images to support the 2006 Network for Calibration and Validation of EO data (NCAVEO) 2006 Field Experiment. DMC is a unique sensor because of its combination of wide swath and high spatial resolution. The data was acquired from UK-DMC at 09:42:53 GMT on the 17th June and consists of three multispectral bands (green, red, near infra-red) with a nominal ground resolution of 32 m. The study area forms a very small part of the whole DMC image, which has a swath width of over 640 km. Other DMC data were obtained from satellites in the constellation operated by Algeria and Nigeria. The NigeriaSat-1 and UKDMC images were taken around the time of the campaign and the AlSAT image a month later. These files have not been geometrically referenced and vary in quality and amount of cloud cover.

As part of the Centre for Ecology and Hydrology Land Cover 2007 Pilot Project, a reconnaissance survey was undertaken on 12th May 2006 in a 60 x 60 km area (bounded by Ordnance Survey National Grid Reference X = 400000 to 460000, Y = 095000 to 155000) which included the Network for Calibration and Validation in Earth Observation (NCAVEO) test site. A recording tablet device was used for acquiring ground data for sample points in the defined area. The dataset consists of an ESRI shape file of point data, containing all the points recorded on a tablet device. Each point has a British National Grid X and Y co-ordinate and a class code. The dataset has not been checked or edited yet and a few of the records will be erroneous. The most obvious errors will be two or more points with identical locations but different codes, the final code will be the correct one. Some of the points for Salisbury Plain lie just outside the test area boundaries. A key to abbreviations used for field recording is also included and a list of thematic land cover classes and their codes to aid field reconnaissance, as used for Land Cover Map 2000.

Centre for Ecology and Hydrology (CEH) Land Cover Map 2000 data are for use at the Network for Calibration And Validation of Earth Observations (NCAVEO) calibration/validation (cal/val) test sites for the illustration and explanation of processes involved in cal/val of earth observation data. The 5 UK test sites which have been identified as example cal/val sites are Barton Bendish, Chilbolton, Harwood Forest, Monks Wood and Thorney Island. The Land Cover Map datasets are available in 25 m derived raster format and Level 2 vector format.