Advances in SIGRID-based formats: Toward a new archive standard

With input from the

GDSIDB Ad-hoc Format Subgroup:H. Andersen (DMI)

C. Bertoia (NIC)

R. Chagnon (CIS)

F. Fetterer (NSIDC)

M. Manore (CIS)

B. Ramsey (CIS)

V. Smolyanitsky (AARI)

F. Fetterer1, H. Andersen, V. Smolyanitsky2, J. Shcherbakov, S. Nauman

1 GDSIDB at the National Snow and Ice Data Center 2 GDSIDB at the Arctic and Antarctic Research Institute

• Vision: All ice services submitting ice chart data regularly and in a standard format to the WMO Global Digital Sea Ice Data Bank (GDSIDB) at AARI and NSIDC

• Goal of this session: Endorsement by IICWG of new archiving format for ice chart data. Format details to be developed by working group of center designates.

SIGRID1 - the current archive format• Developed in 1981 as standard way to digitize international

ice chart data for World Climate Programme, adopted by the WMO CMM Global Digital Sea Ice Data Bank project

• Combination of grid (with min. spacing of 15’) and text encoding of ice chart information

SIGRID: CT46CA309399CB209199CC018799CF1999CN95CD81

Fully Utilized Egg Code: 4-6/3200/7./4.1.7/1/~9 CC/CaCbCc/So/SaSbSc/Sd/

FpFp

• Allows encoding of all egg code information - a plus

• Simplified version (SIGRID II) adopted 1994.

• Vector standard (CONTOUR-2 ) proposed as addition in 1997

1 SIGRID = Sea Ice Grid

SIGRID Reference:Thomas Thompson. 1981. Proposed Format for Gridded Sea Ice Information (SIGRID). Unpublished report prepared for the World Climate Programme.

Some SIGRID characteristics...

Disadvantages of SIGRID

• Ice centers have no easy way to output SIGRID files as part of chart production

• Result - only one service out of 10 GDSIDB participants continues to regularly contribute data to GDSIDB

• Loss of accuracy and resolution from original charts

• Research community must reformat before using SIGRID files

FIRST-YEAR ICE CONCENTRATION

SIGRIDINF:RFAA:099:A7680002400:B0410213:C0015:D06CTCACBCCCNCD SIGRID01:E98201049999:F001=K002:L021163:M0213:R19CT92CA808799CB208499:R02LL …...

SIGRID to EASE-Grid conversion project at NSIDC

EASE-Grid: A grid and projection combination used at NSIDC and elsewhere for satellite and other data of wide spatial extent. The gridded, raster format is favored by most research users of sea ice data.

Regridding SIGRID

Data loss and replication

Data smearing or relocation

(…an argument for archiving vector, not raster, data)

SIGRID has outlived its usefulness as an archive format

for ice chart data

Toward a new format...

• How are ice centers creating charts now?

- GIS• How do ice centers exchange data?

- GIS export

So, look at archiving a GIS output format

Some definitions...• ERDAS Imagine: one commercial GIS software package

• ESRI ARC/INFO: another commercial GIS software package

• ESRI ArcView: desktop GIS software, less complete than ARC/INFO

--- several ice centers are now using one or more of the above• Feature: a representation of a geographic object that has both a spatial

representation (a “shape”) and a set of attributes: in an ice chart, an ice area feature is a polygon described by an egg code.

• Vector: a coordinate-based (x,y) data structure used to represent geographic features using one or more vertices. Attributes are associated with the feature. Contrasted with raster, where attributes are associated with a grid cell.

• Topology: the spatial relationship between connecting or adjacent features.

• Shapefile: An open ESRI spatial data format, does not include topology Create using ESRI or custom software

– 3 main parts: main file (“icechart.shp”, each record is a list of vertices) , index file (“icechart.shx”), and dBASE table(“icechart.dbf”, with feature attributes)

• E00 file: a proprietary ESRI export format, does include topology and projection information

-- e00 files are used as a data exchange format by some ice centers

Both e00 files and shape files can represent ice charts as features (polygons) with associated attributes (a SIGRID encoding of the egg code information).

(NIC egg chart example)

(NIC ice code example)

(NIC shape file example)

Toward a new archive format...

• Vector files can be re-projected or re-scaled without loss of information

• Vector files are easier for most ice centers to produce

• Conversion to raster (at grid size of choice) can take place at archive center

• Shapefiles are an open format

• Centers not using ESRI software can still produce shapefiles, will require programming

• But no projection info

The case for vector over raster files

The case for shapefiles

over e00 files

What can the archive centers be expected to do?

• Ad-hoc format group is experimenting in data formats

• AARI GDSIDB web site shows browser, several format options

• NIC-2-NSIDC proof of concept for conversion of E00 files

AARI and NSIDC can reformat data submitted to the archive in practically any format. BUT resource constraints make it imperative to decide on a standard - work with ice services to find acceptable archive standard

Ad-hoc format group experiments in data formats

Centers to attempt point to grid extraction using supplied grid

”Lon","Lat","Id","Area_id","Ct","Ca","Cb","Cc","Sa","Sb","Sc","Fa","Fb","Fc","So","Sd","Fp","Fs"-19.920000, 69.380000, 383149, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-19.630000, 69.420000, 383150, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-19.330000, 69.460000, 383151, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-19.030000, 69.500000, 383152, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-18.730000, 69.530000, 383153, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-18.430000, 69.570000, 383154, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-18.130000, 69.610000, 383155, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-17.820000, 69.640000, 383156, 902, 45, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, 19, -99-17.520000, 69.680000, 383157, 902, 45, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, 19, -99

”Lon","Lat","Id","Area_id","Ct","Ca","Cb","Cc","Sa","Sb","Sc","Fa","Fb","Fc","So","Sd","Fp","Fs"-19.920000, 69.380000, 383149, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-19.630000, 69.420000, 383150, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-19.330000, 69.460000, 383151, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-19.030000, 69.500000, 383152, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-18.730000, 69.530000, 383153, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-18.430000, 69.570000, 383154, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-18.130000, 69.610000, 383155, 803, 68, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, -99, -99-17.820000, 69.640000, 383156, 902, 45, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, 19, -99-17.520000, 69.680000, 383157, 902, 45, -99, -99, -99, 95, 86, -99, 5, 4, 3, -99, -99, 19, -99

Centers to provide sample shape or e00 file

"000051412_000_ia.e00

EXP 0 /priv_1/siku_data/export/2000051412_000_ia.e00 ARC 2 1 1 3 4 1 2 5 2.8115882E+06 3.7192962E+06 2.8136155E+06 3.7192962E+06 2.8309135E+06 3.7192962E+06 2.8482118E+06 3.7192962E+06 2.8504712E+06 3.7192962E+06 2 1 5 1 1 2 2 2.8719920E+06 3.7192962E+06 2.8826462E+06 3.7193332E+06

"000051412_000_ia.e00

EXP 0 /priv_1/siku_data/export/2000051412_000_ia.e00 ARC 2 1 1 3 4 1 2 5 2.8115882E+06 3.7192962E+06 2.8136155E+06 3.7192962E+06 2.8309135E+06 3.7192962E+06 2.8482118E+06 3.7192962E+06 2.8504712E+06 3.7192962E+06 2 1 5 1 1 2 2 2.8719920E+06 3.7192962E+06 2.8826462E+06 3.7193332E+06

EASE-Grid

EASE-Grid

AARI GDSIDB web site

http://www.aari.nw.ru/gdsidb/gdsidb_2.html

JAVA browser for SIGRID, EASE-Grid formats available forAARI data NIC dataJMA dataBaltic Sea Ice Meeting data

JAVA browser for SIGRID for CIS data

NIC-2-NSIDC

Goal: Convert regional NIC ice charts from regional e00 to arctic-wide EASE-Grid format data files of total concentration.

Result: •Concept demonstrated. •Successful conversion of total concentration. •If project continues, will work with NIC on QC issues (e.g., region “seams” on arctic-wide chart)

Other regions

E00 file

EASE-Grid

Strawman Proposal1. Those ice centers using GIS software for ice chart production will submit files to the GDSIDB data bank in ESRI Shapefile format, with metadata file.

2. Ice attributes attached to individual polygons will be encoded using SIGRID. Additional fields and codes may be defined as appropriate. (Attributes can differ from center to center)

3. A metadata file will be used to describe the content of the shapefile: source of information, dates covered, etc. (Metadata should be standard across centers)

4. The format for the attributes and metadata will be decided by a format working group.

5. The projection will be azimuthal equal area

Item 1: None ?!

Item 2: Currently CIS, NIC, and AARI use different formats of SIGRID ice codes as polygon attributes. Standardize? If no agreement, archive center can adapt.

Item 3: What metadata should be standard? Working group issue

Item 5: If no agreement on projection, or if ice centers do not have resources to reproject from operational projection, archive center can reproject. ARC/INFO has reprojection software bug - need to work with ESRI for fix.

Issues

Next steps

• Need centers using GIS to agree to submit data in shapefiles

• Need POC from each center to work issues

Proposed:AARI -- V. Smolyanitsky, J. ShcherbakovCIS -- R. Chagnon DMI -- H. Andersen NIC -- S. NaumanNSIDC -- F. FettererNorway? (ESRI sw) Finland?(Icemap sw)