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JECAM | Joint Experiment for Crop Assessment and Monitoring

Spain - Barrax / Albacete

Project Overview

Project Objectives:

Crop identification and Crop Area Estimation: Developing methods for crop identification and crop area estimation from HR. 2 maps/ year (winter/summer).
Crop biophysical variables: Estimation of Biophysical variables (LAI, FAPAR, cover fraction). Seasonal monitoring of selected crops (continuous acquisitions). Intensive campaigns (multitemporal) and up-scaling with high resolution imagery.
Mapping biophysical variables from EO data, either from empirical relationship or physically-based methods. 


Project Reports

2017 Site Progress Report

2016 Site Progress Report

Publications:

ImagineS Technical report:

  1. C. Latorre, Camacho, F., Piñó, M.C, de la Cruz, F. (2015). Vegetation Field Data and Production of Ground-Based Maps: Las Tiesas - Barrax site, Spain. May to July, 2015. http://fp7-imagines.eu/media/Documents/ImagineS_RP7.5_FieldCampaign_Barrax2015_I1.00.pdf
     
  2. C. Latorre, Camacho, F., de la Cruz, F., Atienzar, F.  (2014). Vegetation Field Data and Production of Ground-Based Maps: Las Tiesas - Barrax site, Spain. 29th - 30th May, 2014. http://fp7-imagines.eu/media/Documents/ImagineS_RP7.5_FieldCampaign_Barrax2014_I1.10.pdf

Presentations and Proceedings:

  1. C. Latorre, F. Camacho, F.de la Cruz, R. Lacaze, F. Baret, M. Weiss (2014). Seasonal monitoring of FAPAR over the Barrax cropland site in Spain in support of the validation of PROBA-V products at 333 m. 4th International Symposium on Recent Advances in Quantitative Remote Sensing, Torrent, Spain, 22-26 September 2014, (Publ. Univ. Valencia: Valencia), in press.
     
  2. F. Camacho, Lacaze, R., Latorre, C., Baret. F, De la Cruz, F., Demarez, V., Di Bella, C. et al (2015). Collection of Ground Biophysical Measurements in support of Copernicus Global Land Product Validation: The ImagineS database. 12 EGU2015-2209. EGU General Assembly, Vienna, Austria. 12-17 April, 2015
     
  3. F. Camacho, J. Sanchez, C. Latorre, R. Lacaze, M. Weiss, F. Baret, A. Verger, B. Smets (2016). Collection of Ground Biophysical Measurements and Production of High Resolution Ground-based Maps in support of Copernicus Global Land Product Validation: The ImagineS database. ESA living planet Symposium and PROBA-V Symposium. 

Implementation Plans

In situ Data Collection:

Two field campaigns were carried out on 29th March and 12th July, 2016, where two main activities were conducted: a) for crop type identification, and b) for biophysical variables measurements.

Field works were deployed according to the protocol delivered as a result of the FP7 ImagineS Project1 (Camacho et al, 20162). This protocol is in accordance with other scientific developments, as the VALERI project3 the CEOS Land Product Validation group4, and shows the main elements and tasks to perform field campaigns, focused on ground data acquisitions.

 

Since there are two growing seasons, winter and summer, two sampling were conducted, one on 29th March, 2016 and the other on 12th July, 2016, with 92 and 146 crop type plots identified respectively. Figure 3 shows the location of the identified crop type for both campaigns.


Figure 3. Points sampled for crop identification and biophysical parameters on 29 March and 12 July, 2016 in Las Tiesas-Barrax, Spain.

 

In March 2016, biophysical variables (LAI, LAIeff, FAPAR and FCOVER) were measured in 24 Elementary Sampling Units (ESUs) (Fig.3) using digital hemispherical photographs (DHP).  Afterwards, the obtained data was processed with the CAN‐EYE software to provide LAI, LAIeff, FAPAR and FCOVER.  In July, 51 ESUs were sampled (Fig.3), using DHP and including measurements with LAI 2200C plant canopy analizer and Accupar LP80 devices.  These devices were used to measure LAIeff: DHP, AccuparLP80-Ceptometer and LAI 2200C, meanwhile LAI was measured by DHP, FAPAR was measured by DHP and AccuparLP80 and FCOVER was estimated by DHP. Figure 4 shows digital hemispheric photographs acquired at Las Tiesas-Barrax site during the field campaign carried out in July, 2016.


Figure 4. Examples of Digital Hemispheric Photographs (DHP) samples over different surfaces in Las Tiesas-Barrax site on 12th July, 2016.

 

In figure 5, the left shows measurements with LAI2200C over an alfalfa field, the operator is Beatríz Fuster. The right shows measurements with DHP over an alfalfa field; the operator is David Vinué. 

     
Figure 5. Team involved in the field campaign of Las Tiesas site, Barrax (Spain).

 

 

 

Plans for Next Growing Season:


Site Description

Locations

Spain Barrax / Albacete
Site Extent   Centroid: 39.054, -2.100
Top left: 39.167, -2.244 Bottom Right: 38.942, -1.954

Location:
The study area is located in the experimental farm “Las Tiesas” in Barrax (Albacete, Spain), managed by ITAP (Instituto study area is located Técnico Agronómico Provincial, S.A.). Barrax test site is situated within La Mancha, a plateau 700 m above sea level. The centre of the area of study is located at 39.0544, -2.1007.
 

Topography:
This area is characterized by a flat morphology and large uniform land‐use units, surrounded by large areas of cereals. Differences in elevation range up to 2m.
Soils: Moderately well drained. The soil is classified as Petrocalcic Calcixerepts, with a silty‐clayloam texture (13.4% sand, 48.9% silt, and 37.7% clay)

Drainage class/irrigation:
Irrigation infrastructure: sprinklers and pivots. Soil drainage class: moderately well drained

Crop calendar:
Winter and summer crops
 

Field size:
Between 15 and 100 hectares
 

Climate and weather:
Climatic conditions adjust with typical Mediterranean features: high precipitation in spring and autumn and a minimum in summer. The annual rainfall average is around 400 mm. The region has high thermal oscillations during all seasons. La Mancha represents one of the driest regions of Europe consisting of approximately 65% dry land and 35% irrigated land with different agricultural fields. Figure 1 shows examples of landscapes taken in July, 2016 in the study area.

 


Figure 1. Example of landscapes taken in July, 2016 in Las Tiesas Site (Barrax, Spain)

 


Specific Project Objectives & Deliverables

Results

Figure 6 shows the distribution of vegetation types sampled during the field campaigns (data collected over 92 plots on 29th March and 146 plots on 12th July). Also shows that the around 50% of the identified crops correspond to barley fields and bare soil, in March, and bare soil and corn fields in the case of July. The other 50% correspond to a variety of crops, including alfalfa, corn, tree plantation (fruits), onion, sunflower, chickpeas, pappaver, garlic.


Figure 6. Variety and distribution of the identified crops for both campaigns, 29th March and 12th July, 2016.

 

Because of the intense agricultural activity, frequencies of the observations have a great dissimilarity, including the variance due short-term and long-term crops, harvested areas and type of crops. As an example, figure 7 shows LAI frequency distribution for both campaigns.  


Figure 7. LAI frequency distribution in March and July, 2016 field campaigns.

 


Figure 9. Quality Flag (QF) maps based on the convex-hull test over 20 x 20 km2 areas in Barrax, Spain.

 

Transfer functions have been derived by multiple robust regressions between ESU reflectance and the biophysical variables (Martinez et al., 20094). Because the scene presents many senescent and harvested fields, we have selected the NDVI as input for the transfer function (an exponential relationship with LAIeff and LAI, and a linear relationship with FAPAR and FCOVER). NDVI assures good consistency of the maps over the whole area. The biophysical variable maps are available in geographic (UTM 30 North projection WGS‐84) coordinates at 10 m resolution. Figure 10 shows the ground-based LAI maps derived from Sentinel-2A imagery in March and July after transfer function was applied. Figure 10 also shows the difference between LAI values over both seasons, where the scene of July (Fig. 10 right), corresponding to the summer season, showed the lowest LAI values.


Figure 10. Ground-based maps (20x20 km2) retieved at the Barrax site (Sentinel-2 images)

 

The Root Mean Square Errors (RMSE) values for the several transfer function estimated are showed in Table 1.  Results showed acceptable values of the Root Mean Square Error (RMSE) for all the variables undergoing study. Results also showed lower error values in July, maybe because the scene presented many senescent and harvested fields than March scene, i.e. values of the biophysical variables close to 0.


Table 1. Root Mean Square Errors (RMSE) obtained for the LAIeff, LAI, FAPAR and FCOVER in both campaigns for Sentinel-2A images.

Methodology applied to Sentinel-2 was demonstrated as reliable. As NDVI was applied by transfer functions in an exponential and a linear mode for LAI and FAPAR, respectively, final data in biophysical maps is related as in figure 11.


Figure 11. Scatter plots LAI vs FAPAR for the two campaigns at the Barrax Site on 12th March, 2016 (left) and 23rd July, 2016 (right)

 


Figure 12. Correlation between the Sentinel-2 NDVI and Landsat-8 NDVI in the ESUs (12th March, 2016) (right), and random points over the study area (23rd - 18th July, 2016 for Sentinel-2A and Landsat 8, respectively) (left)

 

For the same date, and applying the same methodology to Landat 8 imagery, the visual analysis showed equivalent results, as shown in the figure 13, which confirms a good interoperability of both sensors for mapping biophysical parameters and monitoring its evolution from empirical approaches.  


Figure 13. Ground-based maps (20x20 km2) retrieved at the Barrax Site with Landsat-8 and Sentinel-2 images.

A statistical analysis was performed over the central area of the image (Table 2), focused of the experimental site (5x5Km). Results showed a slight overestimation of Sentinel-2 for each of the variables under study in July 2016, mainly in the estimation of LAI, where the difference between both results is close to 0.6.

Table 2: NDVI, LAI, FAPAR values over a 5x5 km site Las Tiesas(Barrax), 12th March, 2016


Table 3: NDVI, LAI, FAPAR values over 5x5 km site Las Tiesas(Barrax), 18th - 23rd July, 2016

Additionally, 28 random points representing all the NDVI range were compared around the whole image, for both analysis based on transfer functions with Sentinel-2A and Landsat-8 imagery, as shown in figures 14-15 for LAI and FAPAR for March and July images, respectively. Results showed similar FAPAR values for both sensors (Figs. 14-15-b), unlike the results obtained for LAI, where Landsat-8 showed higher values for high LAI values, especially in March, 2016 (figure 14-a). 


Figure 14. Ground-based a) LAI maps and b) FAPAR maps from Sentinel-2A and Landsat-8 versus NDVI map from Sentinel-2 at Barrax site, Spain (12th March, 2016).

 


Figure 15. Ground-based a) LAI maps and b) FAPAR maps from Sentinel-2A (23th July, 2016) and Landsat-8 (18th July, 2016) versus NDVI map from Sentinel-2 at Barrax site, Spain

 

We have accomplished most of our initial objectives, including the performing of ground acquisition and up-scaling of biophysical measurements. We are currently working on analysing methodologies for mapping biophysical variables from physically based and empirically based methods, per crop type and general.

Our guidelines for collecting LAI and FAPAR, as well as for upscaling and producing ground-based maps can be called “best practices”. It has been applied in the FP7 ImagineS to 50 field campaigns. As well to several ESA campaigns (e.g. SEN3EXP, VALSE2), and previously to many of the VALERI sites, showing good performances. It is also included as best practices in the CEOS LPV protocol for global validation of LAI products. 


In Situ Observations

  1. Parameter: Phenological variables
    Data Collection Protocol:

    Since there are two growing seasons, winter and summer, two sampling were conducted, one on 29th March, 2016 and the other on 12th July, 2016, with 92 and 146 crop type plots identified respectively. 

    Frequency: twice a year
  2. Parameter: Biophysical variables
    Data Collection Protocol:

    In March 2016, biophysical variables (LAI, LAIeff, FAPAR and FCOVER) were measured in 24 Elementary Sampling Units (ESUs) (Fig.3) using digital hemispherical photographs (DHP).  Afterwards, the obtained data was processed with the CAN‐EYE software to provide LAI, LAIeff, FAPAR and FCOVER.  In July, 51 ESUs were sampled (Fig.3), using DHP and including measurements with LAI 2200C plant canopy analizer and Accupar LP80 devices.  These devices were used to measure LAIeff: DHP, AccuparLP80-Ceptometer and LAI 2200C, meanwhile LAI was measured by DHP, FAPAR was measured by DHP and AccuparLP80 and FCOVER was estimated by DHP. Figure 4 shows digital hemispheric photographs acquired at Las Tiesas-Barrax site during the field campaign carried out in July, 2016.

    Frequency:

EO Data Requirements

Approximate Start Date of Acquisition: February / March 1
Approximate End Date of Acquisition: September / October
Spatial Resolution: 5-30 m
Temporal Frequency: Every 10 days
Latency of Data Delivery: Every 10 days
Wavelengths Required: G, R, NIR, SWIR
Across Swath: 25km
Along Track: 25km

SAR Data Requirements

Approximate Start Date of Acquisition:
Approximate End Date of Acquisition:
Spatial Resolution:
Temporal Frequency:
Latency of Data Delivery:
Wavelengths Required:
Polarization
Incidence Angle Restrictions:
Across Track:
Along Track:

Locations

Spain Barrax / Albacete

Centroid
Latitude: 39.054
Longitude: -2.100

Site Extent
Top left
Latitude: 39.167
Longitude: -2.100
Bottom Right
Latitude: 38.942
Longitude: -1.954


Optical Sensors

Landsat-8
Imaging Mode: muitlspectral
Spatial Resolution: 30m
Acquisition Frequency: 7-9 days
Pre-Processing Level: L1T Radiance, calibrated /geometrically corrected
Application: Estimation of the high resolution biophysical maps, Atmospheric correction (MODTRAN)

Sentinel-2
Imaging Mode: multispectral
Spatial Resolution: 10-20 m
Acquisition Frequency: 5 days
Pre-Processing Level: L1C orthoimage products, L1T Radiance, calibrated /geometrically corrected
Application: Estimation of the high resolution biophysical maps, Atmospheric correction (MODTRAN)

JECAM | Joint Experiment for Crop Assessment and Monitoring | Group on Earth Observation

©2013 Joint Experiment for Crop Assessment and Monitoring © HER MAJESTY THE QUEEN IN RIGHT OF CANADA SA MAJESTE LA REINE DU CHEF DU CANADA (2012)