dVoy Grid Description Format Considerations

ARC ASCIIGRID refers to a specific interchange format developed for ARC/INFO rasters. The format consists of a header that specifies the geographic domain and resolution, followed by the actual grid cell values. It looks like this:

ncols 157nrows 171xllcorner -156.08749650000yllcorner 18.870890200000cellsize 0.008333000 0 1 1 1 2 3 3 5 6 8 9 12 14 18 21 25 30 35 41 47 5359 66 73 79 86 92 97 102 106 109 112 113 113 113 111 109 106103 98 94 89 83 78 72 67 61 56 51 46 41 37 32 29 25 22 19etc... 

ESRI ASCII Raster

Note: Only allows square grid cells

GeoTiFFProvides information for georeferencing TiFF images.

Geotiff_Information: Version: 1 Key_Revision: 0.1 Tagged_Information: ModelTiepointTag (2,3): 0 0 0 576496.823 4660453.59 0 ModelPixelScaleTag (1,3): 25.400001 25.400001 0 End_Of_Tags. Keyed_Information: GTModelTypeGeoKey (Short,1): ModelTypeProjected GTRasterTypeGeoKey (Short,1): RasterPixelIsArea ProjectedCSTypeGeoKey (Short,1): PCS_WGS84_UTM_zone_17N PCSCitationGeoKey (Ascii,25): "UTM Zone 17 N with WGS84" End_Of_Keys. End_Of_Geotiff.

PCS = 32617 (WGS 84 / UTM zone 17N)Projection = 16017 (UTM zone 17N)Projection Method: CT_TransverseMercator ProjNatOriginLatGeoKey: 0.000000 ( 0d 0' 0.00"N) ProjNatOriginLongGeoKey: -81.000000 ( 81d 0' 0.00"W) ProjScaleAtNatOriginGeoKey: 0.999600 ProjFalseEastingGeoKey: 500000.000000 ProjFalseNorthingGeoKey: 0.000000GCS: 4326/WGS 84Datum: 6326/World Geodetic System 1984Ellipsoid: 7030/WGS 84 (6378137.00,6356752.31)Prime Meridian: 8901/Greenwich (0.000000/ 0d 0' 0.00"E)Projection Linear Units: 9001/meter (1.000000m)

Corner Coordinates:Upper Left ( 576496.823,4660453.588) ( 80d 4'29.95"W, 42d 5'32.78"N)Lower Left ( 576496.823,4518391.383) ( 80d 5'34.76"W, 40d48'46.70"N)Upper Right ( 759427.631,4660453.588) ( 77d51'54.10"W, 42d 3'11.98"N)Lower Right ( 759427.631,4518391.383) ( 77d55'33.34"W, 40d46'32.06"N)

http://remotesensing.org/geotiff/geotiff.html

Adds TiFF compliant tags for projection and coordinate system

GeoTiFF .NET

http://www.positionintegrity.com/geotiff.jsp

OGC Coverage Specification

OGC Grid Coverages are based on GeoTiff but support other formats such as HDF-EOS

Includes interfaces for

• Grid Analysis (histograms and coverage statistics)

• Grid Processing (filtering, smoothing, etc.)

Provides interfaces for getting values from data sets based on location

http://www.opengis.org/techno/specs/01-004.pdf

GML Coverages

Grid Location

Data Value

0 0 3,101.2

1 0 5,101.3

2 0 7,101.4

3 0 11,101.5

0 1 13,101.6

1 1 17,101.7

2 1 19,101.7

3 1 23,101.8

0 2 29,101.9

1 2 31,102.0

2 2 37,102.1

3 2 41,102.2

0 3 43,102.3

1 3 47,102.4

2 3 53,102.5

3 3 59,102.6

OGC’s Geography Markup Language supports Grid Coverages in ASCII and Binary formats

Example for a 3X3 grid with values of temperature and pressure

<AverageTempPressure xmlns="http://www.opengis.net/app" xmlns:gml="http://www.opengis.net/gml" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.opengis.net/app CoverageExamples.xsd"> <gml:domainSet> <gml:Grid dimension="2"> <gml:limits> <gml:GridEnvelope> <gml:low>0 0</gml:low> <gml:high>3 3</gml:high> </gml:GridEnvelope> </gml:limits> <gml:axisName>x</gml:axisName> <gml:axisName>y</gml:axisName> </gml:Grid> </gml:domainSet> <gml:rangeSet> <gml:DataBlock> <gml:rangeParameters> <gml:CompositeValue> <gml:valueComponent> <my:Temperature uom="#C"/> </gml:valueComponent> <gml:valueComponent> <my:Pressure uom="#kPa"/> </gml:valueComponent> </gml:CompositeValue> </gml:rangeParameters> <gml:tupleList>3,101.2 5,101.3 7,101.4 11,101.5 13,101.6 17,101.7 19,101.7 23,101.8 29,101.9 31,102.0 37,102.1 41,102.2 43,102.3 47,102.4 53,102.5 59,102.6</gml:tupleList> </gml:DataBlock> </gml:rangeSet> <gml:coverageFunction/> </AverageTempPressure>

http://www.opengis.org/techno/documents/02-023r4.pdf

Uses ‘envelope’ for bounding rectangle

temp, pres

GML Coverages Example #2

A 15*25 grid of points spaced 12m along the x-axis and 8m along y, with the origin at (600,800) could be encoded:

<map:PointArray gml:srsName="#local" ... > <map:origin> <map:PointArray> <map:origin> <gml:Point> <gml:coord> <gml:X>600</gml:X> <gml:Y>800</gml:Y> </gml:coord> </gml:Point> </map:origin> <map:offset osf:count="15"> <osf:Vector osf:uom="units.xml#m"> <osf:component osf:axis="1"> <osf:Quant>12</osf:Quant> </osf:component> <osf:component osf:axis="2"> <osf:Quant>0.0</osf:Quant> </osf:component> </osf:Vector> </map:offset> </map:PointArray> </map:origin> <map:offset osf:count="25"> <osf:Vector osf:uom="units.xml#m"> <osf:component osf:axis="1"> <osf:Quant>0.0</osf:Quant> </osf:component> <osf:component osf:axis="2"> <osf:Quant>8</osf:Quant> </osf:component> </osf:Vector> </map:offset></map:PointArray>

http://www.ned.dem.csiro.au/XMML/issues/coverage.html

HDF-EOS

Based on HDF 5

Contains Grid/Point/Swath/ZA Interfaces

Metadata includes:

Dimensions

Projection

HDF 5 XML project:

http://hdf.ncsa.uiuc.edu/HDF5/

http://hdfeos.gsfc.nasa.gov/hdfeos/index.cfm

I couldn’t find anything newer than 2 years old

(they have a HDF DTD Schema)

Earth Science Markup Language (ESML)

• Led by the Information Technology and Systems Centerat University of Alabama in Huntsville and NASA

• Specialized markup language for Earth Science information based on XML

• Extends traditional metadata to include both structural and semantic information needed to effect a practical runtime interpretation of a data set

Existing products:

ESML Schema

ESML C++ Library

ESML Java Library

ESML Editor

ESML Data Browser

http://esml.itsc.uah.edu/index2.html

ESML Content Metadata

• Content metadata are mainly used for human knowledge and web-searching

• Content metadata in ESML are derived from FGDC and ECS metadata sets

• Tools are planned for converting existing ECS metadata into ESML

Syntactic Metadata - ASCII Data

ESML supports descriptions of the structures of data files in two basic data formats, Binary and ASCII

Syntactic Metadata - Binary Data

ESML supports descriptions of the structures of data files in two basic data formats, Binary and ASCII

Syntactic Metadata - HDF-EOS

• Self-Describing Formats:–Descriptions of the structures of self-describing data files

through their internal metadata• HDF, HDF-EOS, CDF, netCDF, etc

• Additional data formats can be added as necessary

Writing an ESML File (1)

<a:ESML> <SyntacticMetaData> <Ascii> <AsciiStructure geoInfo="NoGeoInfo" instances="1"> <Field name="SizeX" format="%d">

<Attribute/></Field><Field name="SizeY" format="%d"> <Attribute/></Field><Array occurs="5"> <Array occurs="5"> <Field name="BrightnessTemp"

format="%f"> <Data unit="Degrees Kelvin"/> </Field> </Array></Array>

</AsciiStructure> </Ascii> </SyntacticMetaData></a:ESML>

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

SIMPLE ASCIIDATA FILE

ESML MARKUPFOR THE DATA FILE

<a:ESML> <SyntacticMetaData>

Writing an ESML File (2)

ONLY THESTRUCTURE

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

SIMPLE ASCIIDATA FILE

Writing an ESML File (3)

DESCRIBE THEFORMAT

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

SIMPLE ASCII DATA FILE

<a:ESML> <SyntacticMetaData> <Ascii>

Writing an ESML File (4)

ENTIRE FILE CONTENTSINTO 1 LOGICAL

STRUCTURE

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

SIMPLE ASCII DATA FILE

<a:ESML> <SyntacticMetaData> <Ascii> <AsciiStructure geoInfo="NoGeoInfo" instances="1">

Writing an ESML File (5)

DEFINE THE FIRST FIELD IN THE FILE:

HEADER INFORMATION

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

SIMPLE ASCII DATA FILE

<a:ESML> <SyntacticMetaData> <Ascii> <AsciiStructure geoInfo="NoGeoInfo" instances="1"> <Field name="SizeX" format="%d">

<Attribute/></Field>

Writing an ESML File (6)

DEFINE THE SECOND FIELD IN THE FILE:

HEADER INFORMATION

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

SIMPLE ASCII DATA FILE

<a:ESML> <SyntacticMetaData> <Ascii> <AsciiStructure geoInfo="NoGeoInfo" instances="1"> <Field name="SizeX" format="%d">

<Attribute/></Field>

<Field name="SizeY" format="%d"> <Attribute/></Field>

Writing an ESML File (7)

DEFINE THE DATA FIELD IN THE FILE:PROVIDE SIZE AND

FORMAT INFORMATION

SIMPLE ASCII DATA FILE

<a:ESML> <SyntacticMetaData> <Ascii> <AsciiStructure geoInfo="NoGeoInfo" instances="1"> <Field name="SizeX" format="%d">

<Attribute/></Field>

<Field name="SizeY" format="%d"> <Attribute/></Field>

<Array occurs="5"> <Array occurs="5"> <Field name="BrightnessTemp"

format="%d"> <Data unit="Degrees Kelvin"/> </Field> </Array></Array>

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

Writing an ESML File (8)

CLOSE ALL THETAGS: ESML FILE

IS READY

5 5 1 2 3 4 5 6 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25

SIMPLE ASCII DATA FILE

<a:ESML> <SyntacticMetaData> <Ascii> <AsciiStructure geoInfo="NoGeoInfo" instances="1"> <Field name="SizeX" format="%d">

<Attribute/></Field><Field name="SizeY" format="%d"> <Attribute/></Field><Array occurs="5"> <Array occurs="5"> <Field name="BrightnessTemp"

format="%d"> <Data unit="Degrees Kelvin"/> </Field> </Array></Array>

</AsciiStructure> </Ascii> </SyntacticMetaData></a:ESML>

dVoy Grid Data Type ?

Dimensions

x, y, bounding rectangle

Projection

Projection Type and parameters

Coordinate System (Datum)

Extend the CAPITA HDF layer structure?