Interactive comment on “ EAGLE 2006 – multi-purpose , multi-angle and multi-sensor in-situ , airborne and space borne campaigns over grassland and forest ”

EAGLE2006 – an intensive field campaign for 
the advances in land surface hydrometeorological processes 
– was carried out in the Netherlands from 8th to 18th June 
2006, involving 16 institutions with in total 67 people from 
16 different countries. In addition to the acquisition of multiangle 
and multi-sensor satellite data, several airborne instruments 
– an optical imaging sensor, an imaging microwave radiometer, 
and a flux airplane – were deployed and extensive ground measurements were conducted over one grassland 
site at Cabauw and two forest sites at Loobos and Speulderbos 
in the central part of the Netherlands. The generated data 
set is both unique and urgently needed for the development 
and validation of models and inversion algorithms for quantitative 
land surface parameter estimation and land surface 
hydrometeorological process studies. EAGLE2006 was led 
by the Department of Water Resources of the International 
Institute for Geo-Information Science and Earth Observation 
(ITC) and originated from the combination of a number 
of initiatives supported by different funding agencies. 
The objectives of the EAGLE2006 campaign were closely related to the objectives of other European Space Agency 
(ESA) campaign activities (SPARC2004, SEN2FLEX2005 
and especially AGRISAR2006). However, one important objective 
of the EAGLE2006 campaign is to build up a data 
base for the investigation and validation of the retrieval of 
bio-geophysical parameters, obtained at different radar frequencies 
(X-, C- and L-Band) and at hyperspectral optical 
and thermal bands acquired simultaneously over contrasting 
vegetated fields (forest and grassland). As such, all activities 
were related to algorithm development for future satellite 
missions such as the Sentinels and for validation of retrievals 
of land surface parameters with optical and thermal 
and microwave sensors onboard current and future satellite 
missions. This contribution describes the campaign objectives 
and provides an overview of the airborne and field campaign 
dataset. This dataset is available for scientific investigations 
and can be accessed on the ESA Principal Investigator 
Portal http://eopi.esa.int.

for quantitative land surface parameter estimation and land surface hydrometeorological process studies.EAGLE2006 was led by the Department of Water Resources of the International Institute for Geo-Information Science and Earth Observation (ITC) and originated from the combination of a number of initiatives supported by different funding agencies.The objectives of the EAGLE2006 campaign were closely related to the objectives of other European Space Agency (ESA) campaign activities (SPARC2004, SEN2FLEX2005 and especially AGRISAR2006).However, one important objective of the EAGLE 2006 campaign is to build up a data base for the investigation and validation of the retrieval of bio-geophysical parameters, obtained at different radar frequencies (X-, C-and L-Band) and at hyperspectral optical and thermal bands acquired simultaneously over contrasting vegetated fields (forest and grassland).As such, all activities were related to algorithm development for future satellite missions such as the Sentinels and for validation of retrievals of land surface parameters with optical and thermal and microwave sensors onboard current and future satellite missions.This contribution describes the campaign objectives and provides an overview of the airborne and field campaign dataset.This dataset is available for scientific investigations and can be accessed on the ESA Principal Investigator Portal http://eopi.esa.int.

Campaign overview
To understand the role of the terrestrial hydrosphere-biosphere in Earth's climate system it is essential to be able to measure from space hydrometeorological variables, such as radiation, precipitation, evapotranspiration, soil moisture, clouds, water vapour, surface water and runoff, vegetation state, albedo and surface temperature, etc.Such measurements are required to further increase our understanding of the global climate and its variability, both spatially and temporally.The understanding and quantification of bio-geophysical processes of different vegetated surfaces are prerequisite for the development of validated, global, interactive Earth system models for the prediction of global change accurately enough to assist policy makers in making sound decisions concerning the planning, sustainable use and management as well as conservation of water resources and the environment (GEO, 2005).Multi-sensor remote sensing observations (using radar, thermal and optical data) in combination with in-situ process observations are fundamental for the development and validation of models and retrieval algorithms.
While intensive and extensive field campaigns have been conducted in semiarid areas in recent years for the study of parameter retrievals and land-atmosphere processes using airborne and satellite observations (e.g.Sobrino et al., 2008;Su et al., 2008;Timmermans, 2008b, c), the knowledge of bio-geophysical parameter retrieval from multi-parameter optical, thermal and microwave data and the ability of direct modeling of the underlying physical processes in forests and grassland remain challenging due to lack of appropriate observation data in humid climate.In EAGLE2006 an intensive filed campaign was conducted using different airborne instruments -an optical imaging sensor, an imaging microwave radiometer, and a flux airplane -for data acquisition and to collect extensive ground measurements simultaneously over one grassland site and two forest sites in addition to acquisition of multi-angle and multi-sensor satellite data.As such this data set is both unique and urgently needed for the de velopment and validation of models and inversion algorithms for quantitative surface parameter estimation and land surface hydrometeorological process studies.The EAGLE2006 activities were performed over central parts of the Netherlands (the grassland site at Cabauw and two forest sites at Loobos and Speulderbos; with yearly precipitation around 750 mm and yearly average temperature about 10 • C) from 8 until 18 June 2006.EAGLE2006 originated from the combination of a number of initiatives coming from different funding.As such, the objectives of the EAGLE2006 campaign were closely related to the objectives of other ESA Campaigns, including the SPARC2004 and SEN2FLEX2005 campaigns (Su et al., 2008;Sobrino et al., 2008) and AGRISAR2006 (DLR, 2008).
One important objective of the campaign is to build up a data base for the investigation and validation of the retrieval of bio-geophysical parameters, obtained at different radar frequencies (X-, C-and L-Band) and at hyperspectral optical and thermal bands acquired over vegetated fields (forest and grassland).All activities were related to algorithm development for future satellite missions such as the Sentinels and for validations of data collected with different satellite sensors (e.g.CHRIS, MODIS and MERIS data, with activities also related to AATSR and ASTER thermal data validation, as well as the ASAR sensor on board ESA's Envisat platform and those on EPS/MetOp and SMOS).Most of the activities in the campaign are highly relevant for issues related to retrieval of biophysical parameters from higher reolution data (e.g.CHRIS and MERIS as well as AATSR and ASTER), while scaling issues and complementary between these higher resolution sensors (covering only local sites) and global sensors such as MSG/SEVIRI, EPS/MetOP and SMOS are also key elements.

Campaign objectives
The general purposes of the campaign are: 1. Acquisition of simultaneous multi-angular and multi-sensor data (from visible to microwave domain) over a grassland and a forest.2. Advancement of process understanding in description of radiative and turbulent processes in land-atmosphere interactions.
3. Validation of primary bio-geophysical parameters derived from satellite data using in-situ and airborne data.
4. Improvement of soil moisture retrieval accuracy by synergy of multi-angular (Lband) SMOS and multi-angular C-band SAR/Optical-thermal observations.5. Development of operational algorithms to extract land surface parameters and heat fluxes from the future EPS/MetOp mission.
6. Development of physically based drought monitoring and prediction method (Hydro-climatologic modeling) on the basis of EPS/MetOp observations.
In particular, the EAGLE2006 campaign addressed important specific programmatic needs of Sentinel-1 and -2: 1. To assess the impact of Sentinel-1 and Sentinel-2 sensor and mission characteristics for land applications (land use mapping, parameter retrieval) over forest and grassland.
2. To provide a basis for the quantitative assessment of sensor or mission trade-off studies, e.g.spatial and radiometric resolution.
3. Simulate Sentinel-1 and Sentinel-2 image products over the land (forest and grassland).
In the context of Sentinel-1, EAGLE2006 aimed primarily at the investigation of radar signatures over forest and grassland simultaneously which is currently not addressed.
An important dataset of coordinated in-situ and airborne SAR measurements was collected which provides support both to studies of the Sentinel-1 technical concept, as well as contributing to studies of future mission concepts involving parameter retrieval at L-band.As part of the refinement and verification of the Sentinel-1 technical concept, EA-GLE2006 data will be used for the assessment of land use classification using the proposed nominal operating configuration (i.e.IW mode, VV+HH polarisation plus copolarisation).Simulation of Sentinel-1 image products can be performed using the EAGLE2006 data.
By including an optical data acquisition component, the campaign also provides feedback on key issues relating to definition of the ESA Sentinel-2 multi-spectral mission requirements.Attention focuses on the investigation of the optimum position and width of spectral bands for land cover/change classification and retrieval of bio-geophysical parameters (e.g.improved surface classification, quantitative assessment of vegetation status -forest and grassland).The imaging spectrometer data acquired as part of EAGLE2006 has be used to simulate Sentinel-2 L1b products using the proposed different configurations, and to investigate compatibility with the envisaged L2/L3 products (Timmermans et al., 2008a).
-Loobos, forest, 52 (ABL), land surface conditions and the general weather situation for all seasons.The Cabauw tower is located in a polder 0.7 m below average sea level in an extensive grassland area.In the immediate surroundings of the tower (corresponding to an area of 1 ha) the grass is kept at a height of 8 cm by frequent mowing.Apart from scattered villages, roads and trees the landscape within a radius of at least 20 km consist of flat grassland.Approximately 1.5 km south of the tower runs the river Lek, which is one of the main branches of Rhine.The river Lek is a few hundred meters broad.The water holding capacity of the soil at the site is high, the soil being fine grained with a high content of organic matter.The ground water level in the whole catchment area, within which the field tower is located, is artificially managed through narrow, parallel ditches spaced 40 m apart.The water level in the ditches is always kept at 40 cm below the surface level maintaining the level of the ground water table near the surface.Due to the rich supply of water and the fine grained soil, the evaporative fraction rarely falls below 0.6.More detailed info is provided in Ulden and Wieringa (1996); Beljaars and Bosveld (1997).An overview of recorded data is provided on the web at: http://www.knmi.nl/kodac/ground based observations climate/cabauw.html.

Loobos
The Loobos site (Schelhaas et al., 2004;Dolman et al., 2002;Valentini et al., 2000) is located two kilometers south-west of the village Kootwijk.personal communication).Because of the local topography caused by the sand dunes the distance to the ground water table depends on the location.At the base of the tower the groundwater table dropped in some years to depths of more than 6.5 m below the surface.In a nearby valley the groundwater level varied between 2.0 and 3.6 m below the surface during the observing period.
More detailed information about this site is available on the web-site at: http://www.climatexchange.nl/sites/loobos/.
The Loobos site is also part of the CarboEurope network and data request can be made on the web-site http://gaia.agraria.unitus.it/database/carboeuropeip/.

Speulderbos
The Speulderbos site, operated by the National Institute for Public Health and the Environment (RIVM), is located near the village Garderen approximately 60 km northeast from Cabauw within a large forested area in the Netherlands.A 47-m high scaffolding tower, right panel of Fig. 2, is placed within a dense 2.5 ha Douglas fir stand planted in 1962.The tree density is 785 trees per hectare and the tree height was approximately 22 m in 1995 and 32 m in 2006.The single-sided leaf area index varies between 8 and 11 throughout the year.The surrounding forest stands have typical dimensions of a few hectares and varying tree heights.Dominant species in the neighborhood of the Douglas fir stand are Japanese Lark, Beech, Scotch Pine and Hemlock.At a distance of 1.5 km east from the tower the forest is bordered by a large heather area.In all other directions the vegetation consists of forest at distances of several kilometers.The topography is slightly undulating with height variations of 10 to 20 m within distances of 1 km.
Another tower, currently used by foresters of the state forest service (SBB), in the area is located in the village Drie at about 2 km distance at 52 • 15 54.8 N latitude and 5 • 40 39.4 E longitude.A Large Aperture Scintillometer (LAS) is installed between this and the previous tower to obtain spatial average sensible heat fluxes.
Apart from the existing facilities, this site was selected as an experimental site be-1805 Introduction

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Full cause it had been used in the past for studies in land surface-atmosphere couplings (Bosveld, 1997;Bosvled and Bouten, 2001;Bosveld et al., 1999a, b), hydrological processes (Bouten et al., 1992(Bouten et al., , 1996;;Schaap and Bouten, 1997;Bosveld and Bouten;2003), and soil water dynamics in a forest ecosystem (Bouten and Witter, 1992;Tiktak andBouten, 1992, 1994), thus providing a rich knowledge base for further scientific investigations of land surface hydrometeorological processes.More detailed information about this site and its current instrumentation and measurements is available on the web-site at: http://www.itc.nl/wrs.Base data for the experimental sites include topographic data, digital elevation data, and other ancillary national data (see later).
Topographical data for the entire study area is digitally available, originating from scale 1:50 000 and scale 1:10 000 topographical maps.
Digital elevation data from the Actual Height model of the Netherlands (AHN) is available for the areas of interest.The AHN is a detailed elevation model of the entire country obtained form Airborne Laser Altimetry.The Actual Elevation Model is an initiative of three layers of authorities in the Netherlands, i.e. "Rijkswaterstaat" (Ministry of Transport, Public Works and Water Management), the water boards, and the provinces.As such, it consists of a uniform, country-covering dataset that is commercially available to third parties.Two data formats are available for this dataset; the so-called "base database", which contains filtered elevation points, with X, Y and Z coordinates of the RD (triangulation of national grid) and NAP (Amsterdam Ordnance Datum, the Dutch National leveling reference system), and the grid database of the 5×5 m resolution raster data for the EAGLE2006 campaign.

Satellite data acquisitions
Successful satellite data acquisitions included: MERIS, MODIS, AATSR, ASAR, ASTER, MSG/SEVIRI for the entire campaign period.Figure 3 shows examples of a MERIS and a SEVIRI image.observations.Two types of measurements were performed.In-situ atmospheric soundings were carried out during airborne overpasses at the Cabauw site (Fig. 6).Furthermore routine measurements carried out at De Bilt, KNMI and at the Cabauw tower site are available as well.
The Cabauw tower site is also part of the CESAR (Cabauw Experimental Site for Atmospheric Research) Consortium.This is a consortium of seven national institutes in the Netherlands working together on land-atmosphere and atmospheric research.For the duration of the EAGLE2006 Campaign we have direct access to the data recorded and they are included in the EAGLE2006 database.

In-situ spectrometric, radiometric and goniometric measurements
Other essential measurements include ground based data, including radiometric data (radiometric data in both solar range and thermal range data) and goniometric measurements.Table 2 shows some details of the spectrometric measurements and Fig. 7 illustrates some typical spectral curves.
For the retrieval of land surface emissivity and temperature, radiometric measurements were carried out in the thermal infrared region with various instruments that include fixed FOV and single band or multi bands radiometers.
The measurements included thermal radiometric temperatures, emissivities, atmospheric radiances, air temperature, temperature transects and angular measurements within the site area.Table 3 shows the deployed instruments.The bio-physical measurements made during the EAGLE2006 intensive campaign included vegetation, soil and water measurements.The vegetation measurements included volume and biomass, as well as radiation penetration and Leaf Area Index measurements.Surface roughness for the Cabauw grassland site was measured with stereo photogrammetry using NEar Sensing Camera Field Equipment (NESCAFE).
Soil moisture was measured in the field for calibration and validation of soil moisture measurements through remotely sensed data.
Water quality parameters measured included Secchi depth, turbidity and Chl-a.Unfortunately, it was not possible to take spectra for water quality measurements during the AHS overflight.Due to weather conditions, the first suitable day was 4 July 2006.Measurements were carried out at the open water of the "Wolderwijd" (which was covered by AHS airborne imagery for this purpose but at an earlier date) near the city of Harderwijk.
In order to obtain a high accuracy, detailed 3-D representation of the Speulderbos forest site, necessary for among others within-canopy radiation transfer modeling and surface roughness estimates a laser scanning was carried out around the Speulderbos tower site, using the Leica HDS2500 pulsed laser scanner with a singlepoint range accuracy of ±4 mm, angular accuracies of ±60 micro-radians, and a beam spot size of only 6 mm from 0-50 m range, including point-to-point spacing as fine as 1.2 mm@50 m.The scanner was mounted on the elevator of Speulderbos tower site and made slicing of the forest.An example of such scans is shown in Fig. 9.
The geo-locations of these biophysical measurements were recorded using a Leica 1200 RTK-DGPS.At the Speulderbos site, scintillometer, eddy covariance and radiation measurements were carried out at the top (at 47 m).Other meteorological measurements were conducted just above the canopy crown, around 35 m height.Contact temperatures of different canopy components were measured in the canopy (between 20 and 32 m height), and at ground level.Measurements at ground level were carried out 20 m east of the tower.Table 6 gives an overview of the used instrumentation.
The incoming (R si ) and outgoing (R so ) short wave and long wave (R Li and R Lo ) radiation showed a systematic over-estimation of 10% by the sensor, which has been corrected.
Temperature and relative humidity were measured at 4 heights: 1, 27, 35 and 47 m above the forest floor (Fig. 10).At 1 m height, temperatures are the lowest and relative humidity the highest.In the middle of the canopy, at 27 m, temperatures are the highest and relative humidity the lowest.
A comparison is made between wind speed and direction measured at 34 m height, and those derived from the eddy covariance measurements at 47 m height, which showed a consistent difference in wind direction of about 10 degrees, most likely caused by an error in alignment of the instruments.Wind speed (Fig. 11) is consistently higher at 47 m than at 34 m, as can be expected.Introduction

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Full Soil temperature measured at four depths and soil heat flux measured with three heat flux plates installed at 1 cm below the surface are shown in Fig. 12.
Surface contact temperatures were measured with Negative Temperature Coefficient (NTC) sensors on needles, mosses and trunks at ground level, and on needles, branches and trunks in the canopy between 17 and 34 m height.Figure 13 shows the measured surface temperatures for the sensors at ground level (soil, bold) and in the canopy (canopy, normal) for 17 June 2006.Canopy temperatures are higher than soil surface temperatures.The contact temperatures of the canopy on day 165 until 166 (not shown in Fig. 13) fluctuated very rapidly due to severe rainfall causing the sensors to malfunction.
Two measurement systems were used to measure turbulent fluxes.A Large Aperture Scintillometer (LAS) was used to measure sensible heat flux over the trajectory between the Speulderbos tower and the Drie Forestry tower 2 km north.The receiver was installed at the top of the Speulderbos tower.An eddy covariance system (EC) consisted of a sonic anemometer (CSAT3, Campbell Sci. Inc., USA) combined with a gas analyzer (CS7500, Campbell Sci. Inc., USA) was used to measure sensible heat flux and the exchange of carbon dioxide and water at the top of the Speulderbos tower.Figure 14 shows the components of the energy budget, net radiation, soil heat flux, and sensible and latent heat (upper panel) and the flux of carbon dioxide (lower panel), for a clear day (day 168, 17 June) during the campaign.
In general, the Bowen ratio is approximately unity, but on day 168, a day with high radiation, sensible heat flux is higher than latent heat flux, whereas on a clouded day (day 172 or 21 June, not shown), latent heat flux is higher than sensible heat flux.Figure 15 shows the energy balance closure: available energy (net radiation less soil heat flux) and the sum of sensible and latent heat flux for all observations during the campaign.A 1:1-line is plotted through the data.The sum of the fluxes in general is lower than the available radiation.This known phenomena can either be attributed to an overestimate of available energy (an overestimate of net radiation or an underestimate of soil heat flux), or to an underestimate of the latent and sensible heat fluxes.Introduction

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Full In Fig. 16, the sensible heat fluxes measured with the LAS and with the EC system are compared and a 1:1 line is drawn.In general, the sensible heat flux of the LAS is higher than that of the EC system on cloudy days and lower on clear days.The systematic difference between the two may be attributed to the sensitivity of H LAS to roughness.The difference between the two systems on specific days may be related to different footprints (Timmermans et al., 2009a).A closer examination into the effects of wind direction, precipitation and stability is needed to explain those differences.

Data analysis and preliminary results
The data analysis included simulation of Sentinels (Sentine-1/2) and retrievals of biophysical products.Advanced products that can be expected after further detailed analysis include the following: -Net ecosystem exchange and footprint analysis above forest and grassland (ESA, 2007) -Temperature and emissivity from AHS data (Sobrino et al., 2008) -Modeling fluxes of energy, water and carbon dioxide above the Speulderbos Full details of these data and preliminary products can be found in the EAGLE 2006 final report (Timmermans et al., 2008a), the description of advanced products are given in contributions to the AgriSAR and EAGLE Final Workshop proceedings (ESA, 2007).

Conclusions and recommendations
This contribution describes the mission objectives of the EAGLE2006 intensive field experiment and provides an overview of the airborne and field measurements.A unique dataset has been acquired, including (quasi)simultaneous SAR and optical (hyperspectral, visible and thermal) and atmospheric turbulence airborne datasets as well ground measurements.Atmospheric data from different ground based sensors has been gathered in combination with in-situ atmospheric soundings to characterize the atmospheric conditions during airborne and satellite acquisitions.The SAR data are of high quality at different frequencies (with relevance to Sentinel-1 simulation) and the optical data are of high quality as well (for Sentinel-2 simulation).In addition, the turbulence data and ground data are also of good quality.Analysis showed a high potential of the data for use in further studies as well as a high potential for new product development.With respect to SAR, a combination of Land C-band is preferred for classification purposes and the optical CASI and AHS system specifications are all together optimal for bio-physical parameter retrievals.With respect to the land-atmosphere exchange processes, preliminary analysis of water and energy exchanges have been performed, whereby the thermal data will be an essential input for further analysis of the thermal dynamic characteristics of different canopies and refine the parameterizations in land surface process models.
With respect to potential products for the Sentinel-1 and Sentinel-2 missions, land cover classification maps currently can be considered as in a pre-operational phase.
For soil moisture maps, surface roughness, biomass, fractional vegetation cover and LAI products, the algorithm are in an experimental stage, whereas maps of actual evapotranspiration can be considered as a potential level 3 experimental product as well (providing the thermal input).
We have observed the need for a continuous agricultural data acquisition to cover a bigger variability of the land surface states.To this aspect, a higher crop diversity and variability in surface conditions are needed for future field campaigns.In addi-Figures

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Printer-friendly Version Interactive Discussion tion, multi-temporal, as well as simultaneous observations with both SAR and optical sensors are desirable.With respect to ground observations, a higher data acquisition frequency might be needed, in combination with the need for investigation of the separation between bio-physiological (vegetation growth) and natural (wind, rain) effects.
Preliminary results on retrieval of biophysical parameters are available and the entire EAGLE2006 dataset allows the development of new processing and retrieval algorithms, and the validation of such algorithms by in-situ, airborne and space-borne data.More details on several processing aspects of the data acquired within the campaigns have been presented elsewhere (ESA, 2008).The multi-disciplinary character of the EAGLE2006 field campaign is considered a very strong aspect.Hence, an intensive analysis by the (very) different teams, and external scientific users of the all the collected data should be supported.
All data as acquired in and during the EAGLE2006 Field Campaign are available via the Field Campaign ftp site (ftp.itc.nl/pub/eagle06/EAGLE2006Database/).Access is possible via the ESA Principle Investigator portal http://eopi.esa.int.Meteorol ., 78, 39-69, 1996. Valentini, R., Matteucci, G., Dolman, A. J., Schulze, E.-D., Rebmann, C., Moors, E. J., Granier, A., Gross, P., Jensen, N. O., Pilegaard, K., Lindroth, A., Grelle, A., Bernhofer, C., Continuous micrometeorological measurements have been carried out since 1995 at a height of 23 m above the surface, see middle panel of Fig. 2. In a radius of 500 m 89% of the vegetation consists of pine trees, with an average height of the dominant trees of about 16 m, 3.5% is open vegetation e.g.heather and the remainder is a mixture of coniferous and deciduous trees.The undergrowth of the forest is a closed cover of mainly grass ( Fig. 4. Eleven ESAR flight tracks were carried on 15 June 2006 to cover the three sites of interest flying X-, C-, and L-band configurations, as well as to obtain an X-band DEM.The right panel of Fig. 4 shows a C band polarimetric image of the Cabauw site.The Sky Arrow flux flights were performed over the three tower sites to compare the airborne flux measurements with the tower flux measurements, and also to quantify the exchange of carbon dioxide, sensible and latent heat, momentum fluxes between the biosphere and different vegetated surfaces.Table 1 shows the flight configurations.The flight on 13 June 2006 was performed at the same time as the INTA CASA aircraft mission, to collect flux information and hyperspectral data simultaneously.First results of the profiles flown in the first mission over the different areas are shown in Fig. 5.5 Atmospheric measurementsKnowledge of the atmospheric conditions, its vertical profile and the water vapour content is required to perform accurate atmospheric corrections of space and airborne Introduction Directional and contact measurements were carried out at the Cabauw and Speulderbos sites.Measurements included several land cover units using several instruments between 10 and 18 June 2006.A summary of the goniometric measurements is given in Table4, whereas an example of the measurements over maize at the Cabauw site is shown in Fig.8

Fig. 12 .Figure 13 .
Fig. 12. Soil temperature measured at different depths (upper graph) and soil heat flux measured with three flux plates (lower graph) in Speulderbos versus time of the day, on 17 June 2006.

Fig. 13 .
Fig. 13.Component surface temperatures of 8 sensors on the litter, moss and trunks at ground level (soil), and sensors on trunks, branches and needles in the canopy (canopy) in Speulderbos versus time of the day, on 17 June 2007. 826

• 10 02.8 N, 05 • 44 38 E, 23 m a.m.s.l.
lands near the village of Cabauw.In 1972 at Cabauw a 213 m high tower (left panel of Fig.2) was built by the Royal Netherlands Meteorological Institute (KNMI).This tower was built to establish relations between the state of the atmospheric Four airborne sensors were operated during the EAGLE 2006 campaign to acquire valuable data for bio-/geo-physical parameter estimation over the grassland and forest sites.The AHS from INTA and the CASI sensor of ITRES were both mounted on the CASA 212-200 N/S 270 "Paternina" airplane of INTA.Because the objective of the campaign was primarily aiming at AHS acquisitions the configuration was designed such that if conflicting criteria between AHS and CASI occurred preference was given to AHS.Furthermore, DLR-HR flew a Do228 aircraft that carried their multi-frequency and multi-polarisation Synthetic Aperture Radar system, and ISAFoM operated a Sky-Arrow airplane for flux measurements.Successful AHS and CASI acquisitions were made on 13 June 2006.Two quicklooks are shown in the left and middle panels of Table 5 gives a summary of the locations.IntroductionIn addition to the reference meteorological data (continuous data from Cabauw and Loobos), measurements included standard meteorological measurements at different heights (wind speed and direction, temperature, humidity), sensible heat flux measured with a scintillometer, eddy covariance measurements of heat, water and carbon dioxide transport, contact temperatures of vegetation and soil, soil heat flux, soil moisture content and soil temperature.Measurements were carried out in and near the 44 m tall tower at the Speulderbos site between 7 and 22 June 2006.A mobile LAS system was installed at a grassland site next to the Cabauw tower and operated from 13 June in the afternoon till 20 June 2006 in the morning.

Table 2 .
Summary of spectrometric measurement objectives.

Table 5 .
List of datasets sampled with the Leica RTK-DGPS.

Table 6 .
Meteorological instrumentation Speulderbos.Instruments in italic are owned by Wageningen University, others by ITC.