Today’s theme: Join (Import data file into ArcMap)Why do you need to import external data file into GIS software?• Map files have only geographic information, not other meaningful information, such as income, population, household size... etc.• In order to create thematic maps and analyze them, you need to import those data into GIS.Each geographic feature have an unique identifier.Muninci-palitiesNameMuninci-palitiesNameSubway name/ colorSubway name/ colorRoute numberRoute numberID# for each muni.ID# for each muni.You can import an external data/file into GIS using an unique identifier as a key for association.Muninci-palitiesNameMuninci-palitiesNameRoute numberRoute numberNAME MEDINCMMedford 62409Malden 55557Everett 49876... ...1999medincome.dbfRtNo Traffic1 52,1352A 35,1183 125,721... ...trnsp.dbfFIPS Popu25017010 42,38925017035 24,19425017610 101,355... ...popu2.dbfID# for each muni.ID# for each muni.Finding an unique matching identifier...On ArcMap (GIS): See “Attribute Table”On the raw data side... use Excel or AccessBe sure to remember the field names.They can be different for GIS and the dataIn this case, join by:TOWN (ArcMap) and NAME (.dbf)In this case, join by:TOWN (ArcMap) and NAME (.dbf)How to import...: JOINDifferent field names can be used in different files, even if they contain a same set of identifiers!After you join (import) the data, you can create thematic maps based on the external data.Data missing in the dbf file1999 Median Household
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