(document prepared by Giovanni Schiavon; last update: 22 May 2001)

Table of content

• European RAdar-Optical Research Assemblage (ERA-ORA)
• Content of the Database
• Guidelines
• Database structure

ERA-ORA is a Concerted Action funded by the European Commission within the RTD Programme on Environment and Climate (Fourth Framework Programme) in the field of space techniques applied to environmental monitoring and research.

Institutions from eight European Countries and one international organisation take part in the project:

partner	key person	partner code
CESBIO/Université Paul Sabatier, Toulouse, France	T. Le Toan	upst
DLR, Oberpfaffenhofen, Germany	C. Schmullius,  D. Hounam	dlr
ESA/ESTEC, Noordwijk, Netherlands	M. Borgeaud	esae
Gamma A.G., Muri, Switzerland	T. Strozzi	gamma
Landbouwuniversiteit Wageningen, Netherlands	D. Hoekman	uaw
Universitat de Valencia, Spain	J. Moreno	uval
Università Tor Vergata, Roma, Italy (coordinator)	D. Solimini	urtv
Université Catholique de Louvain, Belgium	A. Guissard	ucl
University of Sheffield, Great Britain	S. Quegan	usfd

Content of the Database

The database includes radar data taken over several land sites in Europe, including bare soil, crops, forest and snow-covered terrain.

For some sites, also simultaneous optical/IR reflectances are available.

Radar signatures and optical reflectances are accompanied by significant ground data (soil moisture and roughness, vegetation biomass, leaf area index, snow water equivalent, etc.).

The database also assembles theoretical models for backscattering simulation.
 

Guidelines

The database has been filled following the guidelines listed below. These have to be considered as indications: in some cases slight modifications have been applied. In any case, the data formats have been reported in "description" files included where needed.

Sections:

1. Ground data for bare soil
2. Ground data for crops
3. Ground data for forests
4. Ground data for snow-covered terrains
5. Scatterometer data
6. Non-polarimetric SAR data
7. Polarimetric SAR data
8. Interferometric SAR data
9. Optical data
10. Directory structure

Notes:

• Each data set is associated with a "homogeneous polygon";
• Radar data are provided with a concurrent ground data set;
• Optical data are provided if concurrent with a radar data set;
• Two data sets are considered "concurrent" if the time difference between the two acquisitions is sufficiently small to make variations of surface properties negligible;
• SAR data are considered polarimetric if HH-VV phase information is available;
• Corrections for eventual slope effects should have been carried out before storing the radar data;
• 8 polygon types are defined:

bsa: bare soil with detailed ground data;
bsb: bare soil with coarse ground data;
cra: crop with detailed ground data;
crb: crop with coarse ground data;
foa: forest with detailed ground data;
fob: forest with coarse ground data;
sna: snow with detailed ground data;
snb: snow with coarse ground data.
A ground data format is defined for each available polygon type.
The definition is given in a file, in the same directory in which ground data are stored. The file also indicates the number of samples per field and the number of measurements per sample. Sections 1-4 contain lists typical of detailed ground data. The experimenter may have stored also coarse ground data, if useful for some applications.

1. Ground data for bare soil

 
• Date and time of measurements;
• Soil type;
• Tillage technique;
• Direction of eventual periodic structures or soil tracks (degrees vs. NS);
• Bulk density (kg/m^3);
• For the available layers:
• Depth of upper layer limit (m);
• Depth of lower layer limit (m);
• Gravimetric moisture (%, average);
• Gravimetric moisture (%, st.dev. or range);
• Profilometer type;
• Profilometer length;
• Profilometer direction (degrees vs. NS);
• Surface height st. dev. (m, average);
• Surface height st. dev. (m, st. dev. or range);
• Correlation length (m, average);
• Correlation length (m, st. dev. or range);
• Profiles data:
• distance between samples,
• number of samples,
• a list containing heights for each sample;
• Available information about stones;
• Available weather information.

 
2. Ground data for crops

 
• Date and time of measurements;
• Crop type and variety;
• Sowing date;
• Phenological state;
• Cover fraction;
• Row direction angle (degrees vs. NS);
• Row separation distance (m);
• Plant separation distance (m);
• Average and st.dev (or range) for the following variables:
• Total height (m);
• Fresh and dry biomass, possibly subdivided among components (kg/m^2);
• Gravimetric moisture (%);
• Stem density (m^-2);
• main stem diameter (m);
• main stem height (m);
• LAI;
• n. of leaves per stem;
• leaf width, length and thickness (m);
• All available data (even if qualitative) on secondary stems, petioles and (in case of wheat or barley) ears, including orientation and non-regularity;
• Available data on canopy stratification;
• The same soil data provided for bare soils, excluding the list of profile data;
• Available weather information.

 
3. Ground data for forests

 
• Date and time of measurements;
• Forest type; species, percentage of species if mixed;
• Age (years);
• Average values and st.dev. (or ranges) for the following variables:
• Row direction vs. NS (degrees);
• Row separation distance (m);
• Tree separation (within row) distance (m);
• Total height (m);
• Dominant tree height (m);
• Canopy height (m);
• Fresh and dry total biomass (kg/m^2);
• Fresh and dry stem biomass (kg/m^2);
• Wood density (kg/m^3) (if available);
• Stem density (m^-2);
• Stem dbh (m);
• Stem height (m);
• LAI;
• Leaf width, length and thickness (m);
• Leaf density (m^-1);
• Leaf orientation distribution;
• Gravimetric moisture content and/or dielectric constant of stem, branches and leaves
• All available branch data (in particular density, branch/stem volume ratio, orientation distribution, dimensions distribution, length/diameter ratio);
• All available understory data (e.g. biomass, typical stem dimensions);
• The same soil data provided for bare soils, excluding the list of profile data;
• Available weather information.

 
4. Ground data for snow-covered terrains

 
• Date and time of measurements;
• Average and st.dev. (or ranges) for:
• Snow thickness (m);
• Snow density (kg/m^3);
• Volumetric liquid content;
• Temperature;
• Permittivity;
• Information on layers;
• Information on grain types;
• % of liquid water;
• The same soil data provided for bare soils, excluding the list of profile data;
• Eventual information on crop type;
• Available information on snow-free terrain.
• Available weather information.

 
5. Scatterometer data

 
• Polygon (field) identification;
• Date and time of acquisition;
• Radar name;
• Frequency (GHz);
• Polarization;
• Off-nadir angle (degrees);
• Azimuth angle (degrees vs. NS);
• Average backscatter coefficient (dB);
• Information to ensure calibration quality.

 
6. Non-polarimetric SAR data

 
• Polygon identification;
• Date and time of acquisition;
• Radar name;
• Frequency (GHz);
• Polarization;
• Off-nadir angle (degrees);
• Azimuth angle (degrees vs. NS);
• N. of pixels;
• N. of looks;
• Average backscatter coefficient (dB);
• Intensity standard deviation;
• Intensity histogram (n. of samles to be selected by the experimenter);
• Autocorrelation function (optional);
• Information to ensure calibration quality.

 
7. Polarimetric SAR data

 
• Polygon identification;
• Date and time of acquisition;
• Radar name;
• Frequency (GHz);
• Off-nadir angle (degrees);
• Azimuth angle (degrees vs. NS);
• N. of pixels;
• N. of looks;
• For the backscatter coefficients in HH, HV, VV and for elements 13, 12, 32 (i.e. HH VV*, HH HV* and VV HV*) of covariance matrix:
• Average value (dB);
• Intensity standard deviation;
• For the polarizations HH, HV and VV:
• Intensity histogram (n. of samples to be selected by the experimenter);
• Autocorrelation function (optional);
• Average value of HH-VV phase;
• Histograms of HH-VV phase (n. of samples to be selected by the experimenter);
• Information on calibration (adopted techniques, eventual problems, etc.).

 
8. Interferometric SAR data

 
• Polygon identification;
• First date and time of acquisition;
• Second date and time of acquisition;
• Radar name;
• Frequency (GHz);
• Polarization;
• Off-nadir angle (degrees);
• Azimuth angle (degrees vs. NS);
• Angle (degrees);
• N. of pixels;
• N. of looks;
• Average backscatter coefficient 1 (dB);
• Intensity standard deviation 1;
• Average backscatter coefficient 2 (dB);
• Intensity standard deviation 2;
• Window size;
• Average degree of coherence;
• Standard deviation of degree of coherence;
• Interferometric baseline (m);
• Information to ensure calibration quality and eventual problems related to the use of two overpasses.

 
9. Optical data

 
• Polygon identification;
• Date and time of acquisition;
• Instrument name;
• N. of pixels;
• For each band:
• Wavelength;
• Average reflectance;
• Reflectance standard deviation;
• Reflectance histogram (n. of samples to be selected by the experimenter);
• Reflectance autocorrelation function (optional);
• Techniques used to consider sun irradiation and correct atmospheric effects.
 
10. Directory structure

/eraora/yourname/data/site/sensor/date (radar/optical data)
/eraora/yourname/data/site/g-data/date (ground data)

where

yourname: partner code
sensor:   ers1, ers2, airsar, ...
site:     choose a 4 characters abbreviation
date:     in the format YYMMDD (YYMMDD_YYMMDD for interferometric data)


file names should be of the type:

sensor data: yourname_sensor_site_date_nnn_typ
ground data: yourname_site_date_nnn_typ

where

• nnn is a progressive file number (nnn for sensor data file is the same as the corresponding ground data file);
• typ is the polygon type (bsa, bsb, cra, crb, foa, fob, sna, snb).

Each file contains ground data or sensor data for a polygon and a date (2 dates for interferometric data). When multifrequency and/or multipolarization and/or multiangle data are available, the same polygon file contains data for all the frequencies and/or polarizations and/or angles, in sequence.

Files are ASCII with one datum per line

each directory with files must contain:

• 1 file with the list of files in the directory
• files describing formats for those available among the 8 types of data.
1 README file in top directory describing directory structure and directory index, and giving references for more detailed information.

Database structure

The database is organized as a tree of directories, starting from the eraora root directory. One subdirectory tree, filled with data and possibly simulation programs, pertains to each partner, according to the following scheme:
 

eraora/	dlr/
	esae/
	gamma/
	uaw/
	ucl/
	upst/
	urtv/
	usfd/
	uval/

The following list describes the tree structure of the ERAORA database. Only non-empty directories are listed together with the names of files containing information on data formats. These names are linked to the files themselves which, therefore, are directly accessible.

eraora/	dlr/	data/	Altmuehltal/	ERS/	readme
				g-data/	readme
			Elbe/	ESAR/	readme
				g-data/	readme
			lechfeld/	daedalus/	readme
				g-data/	readme
			terradew/	ESAR/	readme_ESAR
					140600_a/
					140600_b/
					140600_c/
					160600_a/
					160600_b/
					160600_c/
				g-data/	readme_g-data

eraora/	esae/	data/	readme
			ERS/	Flevoland/	descriptor
					1993/
					1994/
					1995/
					1996/
			g-data/	Flevoland/	1991/
					1992/
					1993/
					1994/
					1995/

eraora/	gamma/	data/	readme.txt
			Bern/	ERS/	descriptor
					950604_950605/
					950709_950710/
					950813_950814/
					951022_951023/
					951126_951127/
					951231_960101/
					960310_960311/
					960414_960415/
				g-data/	descriptor_fo2
					descriptor_sn2
					950604_950605/
					950709_950710/
					950813_950814/
					951022_951023/
					951126_951127/
					951231_960101/
					960310_960311/
					960414_960415/
			CentralPlain/	Rasam/	descriptor
					840705/
					840706/
					840709/
					840710/
					840712/
					840724/
					840727/
					840730/
					840731/
					840904/
					840905/
					840907/
					840911/
					840912/
					840914/
					850501/
					850510/
					850513/
					850611/
					850614/
					850618/
					850628/
					850703/
					850710/
					850814/
					850819/
					850913/
					850917/
					850919/
					851010/
					851031/
					860610/
					860611/
					860814/
					860815/
					871214/
					871218/
					871221/
					871222/
					880105/
					880112/
					880118/
					880126/
					880215/
					880217/
					880218/
					880219/
					880322/
					880411/
					880412/
					880415/
					880426/
					880502/
					880506/
					880511/
					880518/
					880519/
					880524/
					880530/
					880603/
					880607/
					880610/
					880614/
					880615/
					880623/
					880628/
					880704/
					880711/
					880718/
					880811/
					880816/
					880824/
					880909/
					880912/
					880919/
					881005/
					881011/
					881017/
					881024/
					881027/
					881028/
					881124/
					881201/
					881206/
					881213/
					881221/
					890131/
					890201/
					890208/
					890211/
					890212/
					890213/
					890323/
					890410/
					890420/
					890424/
					890501/
					890530/
					890606/
					890612/
					890620/
					890627/
					890706/
					890711/
					890713/
					890719/
					890721/
					890724/
					890726/
					890802/
					890810/
					890816/
					890824/
					890907/
					900510/
					900802/
					901018/
					901019/
					910409/
					910410/
				g-data/	descriptor_bs1
					descriptor_cr1
					840705/
					840706/
					840709/
					840710/
					840712/
					840724/
					840727/
					840730/
					840731/
					840904/
					840905/
					840907/
					840911/
					840912/
					840914/
					850501/
					850510/
					850513/
					850611/
					850614/
					850618/
					850628/
					850703/
					850710/
					850814/
					850819/
					850913/
					850917/
					850919/
					851010/
					851031/
					860610/
					860611/
					860814/
					860815/
					871214/
					871218/
					871221/
					871222/
					880105/
					880112/
					880118/
					880126/
					880215/
					880217/
					880218/
					880219/
					880322/
					880411/
					880412/
					880415/
					880426/
					880502/
					880506/
					880511/
					880518/
					880519/
					880524/
					880530/
					880603/
					880607/
					880610/
					880614/
					880615/
					880623/
					880628/
					880704/
					880711/
					880718/
					880811/
					880816/
					880824/
					880909/
					880912/
					880919/
					881005/
					881011/
					881017/
					881024/
					881027/
					881028/
					881124/
					881201/
					881206/
					881213/
					881221/
					890131/
					890201/
					890208/
					890211/
					890212/
					890213/
					890323/
					890410/
					890420/
					890424/
					890501/
					890530/
					890606/
					890612/
					890620/
					890627/
					890706/
					890711/
					890713/
					890719/
					890721/
					890724/
					890726/
					890802/
					890810/
					890816/
					890824/
					890907/
					900510/
					900802/
					901018/
					901019/
					910409/
					910410/
			Davos/	na-sca/	descriptor
					5-GHz/
					35-GHz/
				g-data/	descriptor_sn1
					5-GHz/
					35-GHz/
			Flevoland91a/	ERS-1/	descriptor
					910904_910910/
					910919_911004/
					911004_911019/
					911019_911109/
				g-data/	descriptor_cr1
			Flevoland91b/	ERS-1/	descriptor
					910904_910910/
					910919_911004/
					911004_911019/
					911019_911109/
				g-data/	descriptor_cr2
			Flevoland95/	ERS/	descriptor
					950629_950630/
					950803_950804/
					950907_950907/
					951012_951013/
				g-data/	descriptor_cr2
			Uecht/	na-sca/	descriptor
					5-GHz/
					35-GHz/
				g-data/	descriptor_sn1
					5-GHz/
					35-GHz/
			Zeeland/	ERS-1/	descriptor
					940106_940115/
					940115_940127/
					940127_940205/
					940205_940211/
					940211_940214/
					940214_940217/
					940217_940220/
					940223_940226/
					940226_940304/
					940304_940313/
					940313_940322/
					940322_940328/
				g-data/	descriptor_bs1
					940106_940115/
					940115_940127/
					940127_940205/
					940205_940211/
					940211_940214/
					940214_940217/
					940217_940220/
					940223_940226/
					940226_940304/
					940304_940313/
					940313_940322/
					940322_940328/

eraora/	uaw/	data/	descriptor
			flev/	airsar/	890816/	descriptor
					910615/	descriptor
					910703/	descriptor
					910712/	descriptor
					910728/	descriptor
				g-data/	890816/	descriptor_bso
						descriptor_cor
						descriptor_pot
						descriptor_sbt
						descriptor_whe
					910615/	descriptor_cor
						descriptor_pot
						descriptor_sbt
						descriptor_whe
					910703/	descriptor_cor
						descriptor_pot
						descriptor_sbt
						descriptor_whe
					910712/	descriptor_cor
						descriptor_pot
						descriptor_sbt
						descriptor_whe
					910728/	descriptor_cor
						descriptor_pot
						descriptor_sbt
						descriptor_whe

eraora/	ucl/	data/	agro.html
		progs/	Example.read
			info_web
			readme
			softman.ps
			index.html

eraora/	upst/	data/	MZeeland/	ers/	descriptor
					010394/
					020294/
					040394/
					050294/
					070394/
					080294/
					100394/
					110294/
					150194/
					240194/
					260294/
					270194/
					300194/
				g-data/	descriptor_bsa
					010394/
					020294/
					040394/
					050294/
					070394/
					080294/
					100394/
					110294/
					150194/
					240194/
					260294/
					270194/
					300194/
			lozere/	ers/	descriptor
				j-ers/	descriptor
				sirc/	descriptor
				g-data/	descriptor
		progs/	vrt/	Donnees/
				bin/
				sources/

eraora/	urtv/	data/	readme
			DESCRIPTION
			mosp/	airsar/	910622/	descriptor
					910629/	descriptor
					910714/	descriptor
				tms/	910701/	descriptor
					910719/	descriptor
				g-data/	910622/	descriptor_bsa
						descriptor_cra
						descriptor_crb
						descriptor_fob
					910629/	descriptor_bsa
						descriptor_cra
						descriptor_crb
						descriptor_fob
					910714/	descriptor_bsa
						descriptor_cra
						descriptor_crb
						descriptor_fob
		progs/	COPYING-2.0
			crop1.f
		washita_cdrom/	Readme.txt
			washita/	readme.txt

eraora/	usfd/	data/	driffield/	readme.txt
				Modelpar.doc
				Trip_1/	descriptor_bsi
					descriptor_cai
					descriptor_cmi
					descriptor_msi
					sensor/	descriptor_msi
					g-data/	descriptor_bsi
						descriptor_cai
						descriptor_cmi
					param/	descriptor
				Trip_2/	descriptor_bsi
					descriptor_cai
					descriptor_cmi
					descriptor_msi
					sensor/	descriptor_msi
					g-data/	descriptor_bsi
						descriptor_cai
						descriptor_cmi
					param/	descriptor
				Trip_3/	descriptor_bsi
					descriptor_cai
					descriptor_cmi
					descriptor_msi
					sensor/	descriptor_msi
					g-data/	descriptor_bsi
						descriptor_cai
						descriptor_cmi
					param/	descriptor
				Trip_4/	descriptor_bsi
					descriptor_cai
					descriptor_cmi
					descriptor_msi
					sensor/	descriptor_msi
					g-data/	descriptor_bsi
						descriptor_cai
						descriptor_cmi
					param/	descriptor
				Trip_5/	descriptor_bsi
					descriptor_cai
					descriptor_cmi
					descriptor_msi
					sensor/	descriptor_msi
					g-data/	descriptor_bsi
						descriptor_cai
						descriptor_cmi
					param/	descriptor
				Trip_6/	descriptor_bsi
					descriptor_cai
					descriptor_cmi
					descriptor_msi
					sensor/	descriptor_msi
					g-data/	descriptor_bsi
						descriptor_cai
						descriptor_cmi
					param/	descriptor
				Trip_7/	descriptor_bsi
					descriptor_cai
					descriptor_cmi
					descriptor_msi
					sensor/	descriptor_msi
					g-data/	descriptor_bsi
						descriptor_cai
						descriptor_cmi
					param/	descriptor
			feltwell/	090-1A/	readme
					c/
					l/
					p/
					ps/

eraora/	uval/	data/	readme.txt
			Descriptor.txt
			Barr/	AVIRIS/	910629/	descriptor.txt
					910715/	descriptor.txt
				Airsar/	910619/	descriptor.txt
					910714/	descriptor.txt
				g-data/	descriptor_bsa.txt
					descriptor_cra.txt
					910612/
					910619/
					910628/
					910714/
					910715/