ESRI ArcGIS Data Interoperability Extension Readers/Writers

1414 Pages·2011·7.56 MB·English

FME® Readers and Writers
® ®
(formats supported by the Esri ArcGIS  Data Interoperability
extension)
About Quick Facts Tables
Eachformat’schapteroverviewincludeshigh-levelinformationabouttheformat’scharacteristics:
Format Type Identifier
EveryformatsupportedbyFMEisuniquelyidentifiedbyanuppercasealphanumericstring.Thisrowliststheunique
identifierforthisformat.Forexample,theidentifierforIGDSDesignisIGDS.Theformattypeidentifierisusedin
mappingfilesonREADER_TYPEandWRITER_TYPElinestodefinethereaderandwritertobeusedfortrans-
lation.InFMEObjects,whenareaderorwriteriscreated,theformattypeidentifierisusedtospecifyitstype.
Reader/Writer
FMEtypicallyallowsreadingfromandwritingtoasupporteddataformat.However,someformatssupporteitherread-
ingorwriting,butnotboth.Thisrowspecifieswhetherreadingonly,writingonly,orreadingandwritingisavailable
forthisformat.
LicensingLevel
SomeFME-supportedformatsrequirespecificlicensing.Forexample,certainformatsarenotsupportedinFMEBase
Edition.Thisrowliststheminimumlicensinglevelrequiredtoreadfromorwritetotheformat.
Dependencies
Someformatsrequiretheinstallationoftheapplicationassociatedwiththeformat,ormayrequireanextra-costplug-
in.
Dataset Type
FMEreadsfeaturesfromdatasetsandwritesfeaturestodatasets.Thedefinitionofadatasetvariesbetweendifferent
readersandwriters,dependingnatureoftheformat.Thisrowspecifiesthetypeofdatasetusedbythisformat.
FileDataset:Themostbasictypeofdatasetisthefiledataset:asinglefilewhoseextensionisincludedinthelistof
supportedfileextensions.Afiledatasetreaderopensthespecifiedfileandreadsitsfeatures.Afiledatasetwriter
createsthespecifiedfileifitdoesn'texistandwritesfeaturesintoit.Ingeneral,filedatasetwritersoverwriteexisting
files,butsomecanappendtoexistingfiles.
Directory Dataset:Adirectorydatasetconsistsofadirectoryspecification.Adirectorydatasetreaderexaminesthe
nameofallthefilesinthespecifieddirectoryandreadsthosefileswhoseextensionsareincludedinthelistofsup-
portedfileextensions.Theorderinwhichfilesarereadisnotdocumented.Manydirectorydatasetreadersprovide
anoptiontoexplicitlynameasubsetofthedirectory'sfilesthataretoberead.Adirectorydatasetwritercreatesthe
specifieddirectoryifitdoesnotexist.Ingeneral,ifthedirectorydoesexist,anyfilesinthedirectorythatmatchthe
nameofoutputfileswillbeoverwritten;however,somedirectorydatasetwriterscanappendtoexistingfiles.
DatabaseDataset:Adatabasedatasetconsistsofasetofinformationneededtoconnecttoadatabaseschema.A
databasedatasetreaderreadsallthetablesinthespecifieddatabaseschema.Theorderinwhichtablesarereadis
notdocumented.Manydatabasedatasetreadersprovideanoptiontoexplicitlynameasubsetoftheschema'stables
thataretoberead.Anytablesinthespecifieddatabasethatmatchthenameofoutputtableswillbeoverwritten.
URL Dataset:AURLdatasetconsistsofauniformresourcelocator.AURLdatasetreaderconnectsoveranetworkto
aremoteserverandretrievesthedataprovidedbythatresource.
Typical File Extensions
Mostfiledatasetreaderswillreaddatafromanylegally-namedfile,independentofextension.
Mostformatsareassociatedwithoneormorefileextensions.Thisrowliststhefileextensionstypicallyassociated
withthisformat.Whenaformatusesseveralfileswiththesamebasenamebutdifferentextensions,theprimary
extensionislistedfirstandtheancillaryonesarelistedinparentheses.
Automated Translation Support
TheFMEtypicallyallowsautomatedtranslationtoandfromasupporteddataformat.However,someformatssupport
eitherautomatedreadingorautomatedwriting,butnotboth.Thisrowspecifieswhetherthisformatsupportsauto-
matedreading,writing,orboth.Whenautomatedtranslationisnotavailable,acustommappingfilemustbeused.
Feature Type
EveryformatsupportedbyFMEidentifiesthefeaturesinitsdatasetsaccordingtoawell-defineddataclassification
scheme.Thisprimaryclassificationisknownasthefeature'stype,whichservesasthemainhandletoafeature.This
rowdescribestheformat’sclassificationscheme.Forexample,asimpleclassificationschemeistoidentifyfeatures
accordingtothefileortabletheyresidein(thefeature'stypeisthefilebasenameortablename,respectively).For
level-basedformats,featuresaretypicallygroupedbylevel(thefeature'stypeisthelevelinwhichitresides).
Anothercommonclassificationistogroupfeaturesaccordingtothethematiclayertowhichtheybelong–forexam-
ple,roads,railways,andrivers.Althoughthesearethemostcommonclassificationschemes,thelistofpossible
schemesisquitebroadbecausetheclassificationchosenisindividualtotheformat.
User-Defined Attributes
AnFMEfeatureconsistsofgeometryandattributes.Whilemanyofafeature'sattributesarepredefinedbyFMEand
thefeature'sformat(suchattributesareconstantfromonedatasettoanother),someformatsallowuserstodefine
customattributes.Theseuser-definedattributesgivetheformatflexibilitytostorearbitraryamountsofdomain-spe-
cificinformationinadditiontogeometry.Thisrowspecifieswhetherthisformatsupportsuser-definedattributes.
Coordinate System Support
Thisrowindicateswhetherdatasetsofthisformatcanstorecoordinatesysteminformation,andifso,whetherthe
readerextractsthisinformation.
Generic Color Support
Thefme_colorandfme_fill_colorfeatureattributesrepresentthered,green,andblueintensitiesofafea-
ture.Intensitiescaneachvarybetween0.0and1.0,andarecalculatedbytakingthecolorintensityanddividingitby
thetotalintensityrange.Thisrowindicateswhetherornottheformatsupportsthegenericfme_colorandfme_
fill_colorattributes.
Ifaformathasgenericcolorsupport,thereaderwilladdboththegenericFMEcolorattributesandtheformat-spe-
cificcolorattributestofeatures.Writersthatsupportgenericcolorwillgiveprecedencetotheformat-specificcolor
attributesiftheyarepresentinadditiontothegenericattributes.
SincebothgenericFMEattributesandformat-specificattributesexistonworkspacefeatures,itisimportanttonote
thattheco-existenceofthetwotypesofattributescansometimescauseaconflict,andtheformat-specificattrib-
utewillbedeleted.Formoreinformation,seeFormat-SpecificAttributesandGenericFMEAttributesinWorkbench.
Spatial Index
Thisrowappliesonlytoreaders:itindicateswhetherornotthenativereadersupportsspatialindexing.Thepossible
valuesare:
Never:Thisreaderneverprovidesaspatialindex.
Optional:Thisreadermayormaynotprovideaspatialindex,dependingonwhetherornotoneisavailableforthe
specificdatasetbeingread.
Always:Thisreaderalwaysprovidesaspatialindex.
Schema Required
Thisrowappliesonlytowriters.Formappingfiles,itindicateswhetherornotDEFlinesarerequired.ForFME
Objectsapplications,itindicateswhetherornotschemafeaturesneedtobeprovidedtothewriterbeforedatafea-
turescanbewrittentoadataset.
Encoding Support
Thisrowindicateswhetheraformatsupportscharacterencodingschemesforattributevalues.Userswhoneedto
translatetheirinternationaldatawillbenefitfromthisenhancedsupportastheywillnolongerneedtosettheir
defaultsystemlanguage(onWindows,thisissetthroughthe"RegionalandLanguageOptions"dialog)tomatchthe
encodingofthedata.Dependingontheformat,thecharacterencodingmayneedtobespecifiedbytheuser.
Transaction Support
Thisrowappliesonlytoreaders:itindicateswhetherornotthenativereadersupportstransactionprocessing.For
mappingfiles,itindicateswhetherornotthestartingtransactionnumberandthetransactionintervalcanbespec-
ified.ForFMEObjectsapplications,itindicateswhetherornottheuniversalwriterobjecthonorsthestart-
Transaction,commitTransaction,androllbackTransactionmethods.
Enhanced Geometry
Indicateswhetherthereader/writersupportstheenhancedgeometrymodel.Theadditionofenhancedgeometry
modelsupportallowslinesandpolygonscontainingarcstobemaintained,ratherthanstrokedorthegeometrysplit
upintomultiplesegments.Italsoprovidestheabilitytotrulyholdmeasures.
Gotohttp://www.fmepedia.com/index.php/Geometry_Modelformoreinformation.
Formoreinformationontheglobaldirectivethatsetstheusageofenhancedgeometryinreadersandwriters(aswell
asfunctions,factoriesandtransformers),seetheFMEFundamentalson-linehelp,inFMEConfiguration>Geometry
Handling.(TheFMEFundamentalshelpisavailableasalinkfromanyhelpmenu.)
Geometry Type Attribute
Thenameofthefeatureattributethatcontainsthefeature'sformat-specificgeometrytype.
Supported Geometry
Thistableindicateswhichgeometrytypestheformatsupports.
Geometry Support
Geometry Supported? Geometry Supported?
aggregate yes/no point yes/no
circles yes/no polygon yes/no
circular arc yes/no raster yes/no
donutpolygon yes/no solid yes/no
elliptical arc yes/no surface yes/no
ellipses yes/no text yes/no
line yes/no z values yes/no
none yes/no
Raster-Specific Information
Inanyrasterformat,thistableprovidesadditionalraster-specificinformation.SeeAboutFMERastersformoreinfor-
mationoneachentry.
BandInterpretations Red8, Green8, Blue8
Palette Key Interpretations notapplicable
Palette Value Interpretations notapplicable
Nodata Value 0,0,0
Cell Origin(x, y) 0.5, 0.5
RotationSupport No
GCPSupport No
WorldFile Support No
TABFile Support Yes
About Feature Attributes
Featureattributesarecategorizedintooneofthefollowingthreegroups:
1. format-specificattributes
2. userattributes
3. genericFMEattributes
Afeaturemayhaveoneormoreassociatedformatattributes.Aformatattributerepresentsanattributethatisspe-
cifictoaformat.Someexamplesare:autocad_block_nameandsde30_justification.
Afeatureisalsoassociatedwithoneormoreassociateduserattributes,whichrepresentcustomattributesthathold
domaininformationaboutafeature,suchas:parcel_identifier,owner_name,date_surveyed,etc.
GenericFMEattributenamesareprefixedbyfme_.Thebenefitofusinggenericattributesoverformat-specificattrib-
utesisthattheyhavethesamemeaninginallthereadersandwritersthatsupportthem.Forexample,thefme_
colorandfme_fill_colorfeatureattributesrepresentthered,green,andblueintensitiesofafeature.Ifafor-
mathasgenericcolorsupport,thereaderwilladdboththegenericFMEcolorattributesandtheformat-specificcolor
attributestofeatures.Writersthatsupportgenericcolorwillgiveprecedencetotheformat-specificcolorattributesif
theyarepresentinadditiontothegenericattributes.
Themostimportantgenericattributesarefme_typeandfme_geometry.Bothoftheserelatetothegeometryof
afeature.TheGeometryclassrepresentsafeature’spositionalinformation.Featuregeometrymayconsistofpoints,
lines,orareas.Featuresthatcontainmultiplegeometricpartsaresaidtohaveanaggregategeometry.Featureswith
nogeometryarealsosupported.
Thedistinctionbetweenfme_typeandfme_geometryisanimportantone:fme_geometryindicatesthe
geometrytypeoftheactualcoordinates,whereasfme_typespecifieshowthatgeometryistobeinterpreted.For
example,apointgeometrytypecanbeinterpretedasoneofthefollowingFMEtypes:point,arc,ellipse,ortext.The
validcombinationsoffme_typeandfme_geometryareshowninthetablebelow:
fme_
fme_ fme_ fme_ fme_ fme_ fme_
no_
geometry point line polygon donut aggregate
geom
fme_type
fme_point X X
fme_arc X
fme_ellipse X
fme_text X
fme_line X X
fme_area X X X
fme_undefined X
Format-Specific Attributes and Generic FME Attributes in Workbench
SincebothgenericFMEattributesandformat-specificattributesexistonworkspacefeatures,itisimportanttonote
thattheco-existenceofthetwotypesofattributescansometimescauseaconflict.Ifthishappensbetweenareader
andawriter,thegenericfmeattributewilltakeprecedence.
Forexample,ifafeaturecontainsaformat-specificcolorspecification,andtheoptionalfme_colorattributeis
changedbetweenthereaderandthewriter,fme_colorwilltakeprecedenceandtheformat-specificcolorspec-
ificationwillbedeletedfromtheworkspace.(However,ifafeaturewithinawritercontainsaformat-specificcolor
specification,thenthatwillsupersedefme_color.Seethesectiononfme_colorintheFMEFundamentalsmanual.)
Thispossibleconflictalsoappliesifyoualterafeature’sgeometryinaworkspacethathasthesamesourceanddes-
tinationformat.Ifyoualterthegeometryfromthereadertothewriter,thenthegenericfme_typewillbeused,and
theformat-specificgeometrytypewillbedeleted.
SeetheListof Format-Specific Attributes andCorrespondingFMEGeneric Attributes.
List of Format-Specific Attributes and Corresponding FME Generic Attributes
TheapplicableformatattributesandcorrespondingFMEattributesarelistedbelow.Anychange(includingdeletion)
tothefme_*attributebetweenareaderandwriterwillcausetheformat-specificattributetobedeleted.
CorrespondingGeneric
Format Format-SpecificAttribute
FMEAttribute
AutoCAD fme_color
CGDEF cgdef_color.red fme_color
cgdef_color.green
cgdef_color.blue
Design(v7andv8) igds_color fme_color
igds_color.red
igds_color.green
igds_color.blue
igds_fill_color fme_fill_color
igds_fill_color.red igds_fill_color
igds_fill_color.green
igds_fill_color.blue
PenMetrics GRD grd_pen_color fme_color
grd_layers_pen_color
grd_blocks_pen_color
grd_brush_color fme_fill_color
grd_layers_brush_color
grd_blocks_brush_color
IDEX idex_database_color fme_color
idex_database_hatch_color fme_fill_color
MapInfoNative format mapinfo_brush_foreground fme_fill_color
(MAPINFOandMITAB)
mapinfo_pen_color fme_color
mapinfo_symbol_color
mapinfo_text_fontfgcolor
CorrespondingGeneric
Format Format-SpecificAttribute
FMEAttribute
MIF/MID(MapInfoData mapinfo_brush_foreground fme_fill_color
Interchange Format)
mapinfo_pen_color fme_color
mapinfo_symbol_color
mapinfo_text_fontfgcolor
StruMap strumap_red fme_color
strumap_green
strumap_blue
strumap_color
Simple Geometries
Simplegeometriesaregeometriesthatarenotcomposedofothergeometries,anddonothaveassociatedgeneric
FMEattributesthataffecttheirpositionalrepresentation.Moreconcretely,featureswithsimplegeometriesarethose
withthefollowingcombinationsoffme_geometryandfme_type:{fme_line, fme_line}, {fme_
point, fme_point}, {fme_polygon, fme_area}.
Arc and Ellipsoid Geometries
Featureswithellipsoidgeometryarethosewithfme_geometryequaltofme_pointandfme_typeequalto
fme_ellipse.
Donut Geometries
DonutGeometriesareusedtorepresentareafeatureswithholes,suchalakeswithislands.AproperDonutGeometry
containsonlypolygonsthatdonotoverlapeachotherorsharecommonedges;alloftheinnerpolygonsaredisjoint
andfullycontainedwithintheouterpolygon.However,FMEdoesnotguaranteethatallfeatureswithdonutgeometry
followtheserules.Forexample,whendataisreadfromadatasourcethatsupportsdonutgeometriesbutdonot
enforcenon-intersectingandnon-overlappingdonuts,FMEwillrespecttheoriginalgeometry.Thefigurebelow
showsanexampledonutgeometry.
Featureswithdonutgeometryarethosewithanfme_geometryequaltofme_donutandanfme_typevalue
equaltofme_area.
Aggregate Geometries
Afeaturewithaggregategeometryhasanfme_geometryvalueequaltofme_aggregateandanfme_type
valueequaltoeitherfme_point,fme_line,orfme_area.FMEusesaggregatestorepresentfeatureswith
multi-partgeometries:geometriesthatarecomposedofseveraldisjointpieces.Inmostsituations,thecomponents
ofanaggregatearehomogeneous.Thatis,iffme_typeisfme_point,thentheaggregatecontainspointgeom-
etries;iffme_typeisfme_linethentheaggregatecontainslinegeometries;andsoon.However,yourappli-
cationshouldbedesignedtohandlenon-homogeneousaggregatesgracefullysinceitispossiblethatsomedata
sourcesmaycontainsuchfeatures.Non-homogeneousaggregateshavenovalueforfme_type.
OpenGIS Geometries
TheOpenGISConsortiumdefinesaWell-KnownText(WKT)representationforfeaturegeometries.TheFME-
OFeatureobjectallowsyourapplicationtoimportageometryfromWKTandexportageometrytoWKTusingthe
importGeometryFromOGCWKTandexportGeometryFromOGCWKTmethodsrespectively.
About FME Rasters
Overview
RasterdatainFMEisrepresentedbyfeatureswithrastergeometry.Rasterdatadiffersinseveralkeywaysfromvec-
tordata,andishandleduniquelyinFME.Arastercanbeconsideredasagridofvaluesorganizedintorowsandcol-
umns,withtherelativesizeofitscellsdeterminingitsresolution,orlevelofdetail.Eachrowandcolumnintersection
inrastergridiscalledacellorpixel.Vectorpointgeometriescanoftenbethoughtofasanalogoustocells,whilelin-
eargeometrieslikeroadsarerepresentedascontiguouscells.Vectorfeaturestendtobemoremeaningfulwhen
takentogetherasagroup,whileasinglerasterfeaturecanconveythesamespatialinformationinanon-modular
fashion.
Oftenarasterservesasabackdropforoverlayingspecificvectorinformation.Forexample,youcanplacevectorlines
andpolygonsthatrepresentstreetsandbuildingsonarasterimagethatisanaerialphotographofacity.Conversely
rastermaybeusedasabackdropforcreatingvectormaps.Forexample,onemightusesatelliteoraerialimageryto
mapparticularfeaturesofanurbanenvironmentforcityplanningorgeologicstructuresforlocatingnatural
resources.
Rasterscanberepresentedaseitherimageornumericdata.Imagesarecommonlyderivedfromsatellitedataorpho-
tography,whilenumericdataoftenrepresentselevations,temperatures,andotherquantitativeinformation.
Rasterdataisstoredinoneormorebandswhosepropertiesmayormaynotbehomogeneous.Imagerydataoften
containsseveralbandsofdata.ThisdatamaycomefromeitherOpticalorSAR(SyntheticApertureRADAR)typesen-
sorsandmaycontainanynumberofimagebandsofdatarelatingtoawiderangeofspectralbandsorpolarizations.
Thoughabandmayhaveitsownspecificbandproperties,allbandsonarastermustshareacommonsetofraster
propertiessuchasthenumberofrowsandcolumns,thecellsizeandthegroundextents.
Abandmayoptionallyhaveoneormorepalettes,alsocalledcolormapsorLook-UpTables(LUTs),associatedwithit.
Apaletteisessentiallyalookuptableofdiscretekeystocolororstringvalues.Theserastersareoftenreferredtoas
classifiedbecauseofthediscretedataranges.Classifiedrastersoftenservethepurposeofprovidingavisualrep-
resentationorprovidingadditionaldescriptiveinformationforspecificareasofaraster.
About FME Rasters
Overview
RasterdatainFMEisrepresentedbyfeatureswithrastergeometry.Rasterdatadiffersinseveralkeywaysfromvec-
tordata,andishandleduniquelyinFME.Arastercanbeconsideredasagridofvaluesorganizedintorowsandcol-
umns,withtherelativesizeofitscellsdeterminingitsresolution,orlevelofdetail.Eachrowandcolumnintersection
inrastergridiscalledacellorpixel.Vectorpointgeometriescanoftenbethoughtofasanalogoustocells,whilelin-
eargeometrieslikeroadsarerepresentedascontiguouscells.Vectorfeaturestendtobemoremeaningfulwhen
takentogetherasagroup,whileasinglerasterfeaturecanconveythesamespatialinformationinanon-modular
fashion.
Oftenarasterservesasabackdropforoverlayingspecificvectorinformation.Forexample,youcanplacevectorlines
andpolygonsthatrepresentstreetsandbuildingsonarasterimagethatisanaerialphotographofacity.Conversely
rastermaybeusedasabackdropforcreatingvectormaps.Forexample,onemightusesatelliteoraerialimageryto
mapparticularfeaturesofanurbanenvironmentforcityplanningorgeologicstructuresforlocatingnatural
resources.
Rasterscanberepresentedaseitherimageornumericdata.Imagesarecommonlyderivedfromsatellitedataorpho-
tography,whilenumericdataoftenrepresentselevations,temperatures,andotherquantitativeinformation.
Rasterdataisstoredinoneormorebandswhosepropertiesmayormaynotbehomogeneous.Imagerydataoften
containsseveralbandsofdata.ThisdatamaycomefromeitherOpticalorSAR(SyntheticApertureRADAR)typesen-
sorsandmaycontainanynumberofimagebandsofdatarelatingtoawiderangeofspectralbandsorpolarizations.
Thoughabandmayhaveitsownspecificbandproperties,allbandsonarastermustshareacommonsetofraster
propertiessuchasthenumberofrowsandcolumns,thecellsizeandthegroundextents.
Abandmayoptionallyhaveoneormorepalettes,alsocalledcolormapsorLook-UpTables(LUTs),associatedwithit.
Apaletteisessentiallyalookuptableofdiscretekeystocolororstringvalues.Theserastersareoftenreferredtoas
classifiedbecauseofthediscretedataranges.Classifiedrastersoftenservethepurposeofprovidingavisualrep-
resentationorprovidingadditionaldescriptiveinformationforspecificareasofaraster.
Raster Properties
Rasterscontainasetofmetadatathatdefinesthepropertiesfortherasterasawhole.Thesepropertiesinclude
l numberofbands(channelsorlayers)
l numberofrowsandcolumns(linesandpixels)
l cellsize(spacing)
l cellorigin
l extents
l rotation
l GroundControlPoint(GCPs)
Acellistherectangularareacreatedinthexandydimensionsbythespacingofpixelsfromtherasterorigin.
Spacingorcellsizeisthefixeddistanceinthexandydimensionsbetweeneachpixelintheraster.Someformats
storeonlyonespacingvalue,meaningthatitmustbethesameforboththexandydimensions–thisisoften
referredtoassquarecells.
Therasteroriginisthelowerleftxandyoftherasteratwhichthecoverageofthedatasamplebegins.Itcontainsthe
minimalxandminimalyvaluesfortheraster.InFME,therasteroriginisthelowerleftcornerofthelowestandleft-
mostcellintheraster.
Celloriginisthepointwithineachcellofarasterfromwhichthepixelforthatcellisderived.Thelowerleftcornerof
thecellinthexorydimensionis0.0,whiletheupperrightcorneris1.0.Acelloriginof0.5inxand0.5inywould
putthedatapointforeachcellinthecenterofthecell,whichisthedefaultrepresentationinFME.
Extentsorboundsforarasterarerepresentedbythelowerleftgroundcoordinateandtheupperrightcoordinatecov-
eredbytherasterdata.Thisissometimesreferredtoascellbounded.Theminimumxandmaximumyvaluesthat
comprisetheupperleftcorneroftherasterextentsareequivalenttotherasterorigin.
RotationisameasureoftheangleinradiansoftheCCWrotationoftherasterfromthepositivexaxis.Therotation
pointisthetopleftcornerofthetopleftcelloftheimage.Notethatcurrentlytherotationisnotappliedduringfactory
orfunctionrelatedprocessingbutismerelybeingstoredatthispoint.Rotationdoesnotaffecttheextentvaluesand
isconsideredaseparateproperty.
GroundControlPoints,orGCPs,mayalsobepresentinthegeometryofaraster.Ifpresent,theserefertoasetof
pointsusedtogeoreferenceimageorelevationdata,witheachpoint'tying'arowandcolumnlocationintherasterto
anx,ylocationontheearth.AcoordinatesystemwillalsobepresentinthepropertiesofarastercontainingGCPs,as
opposedtobeingstoredonthefeatureitself.GCPscaneitherbeappliedtotherasterresultingintheimagebeinggeo-
referencedandtaggedwiththeGCPcoordinatesystem,ortheGCPscanbeextractedandstoredontheresultingdata
fileforthoseformatssupportingunreferenceddataandGCPstorage.
Band Properties
Rasterscontainasetofmetadatathatdefinesthepropertiesforeachband.Thesepropertiesincludethebandname,
numberofpalettes,interpretation,bitdepth,'nodata'value,andpropertiesrelatingtothepreferredmethodofdata
access.
Theinterpretationofabanddescribesthetypeofdatastoredateachcellintherasterandnumberofbitsusedfor
thattype.Aninterpretationalsoimpliesanunderlyingfundamentaldatatypeusedtostorethedata.Forexample,an
interpretation'Gray8'impliesthattheactualdatatypeisFME_UInt8andthatthesizeofeachcellis8bits.Possible
interpretationvaluesareInt8,Int16,Int32,Int64,UInt8,UInt16,UInt32,UInt64,Real32,Real64,Gray8,Gray16,
Red8,Red16,Green8,Green16,Blue8,Blue16,Alpha8,Alpha16.