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School of Geography FACULTY OF ENVIRONMENT Working with Tables 1.

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Presentation on theme: "School of Geography FACULTY OF ENVIRONMENT Working with Tables 1."— Presentation transcript:

1 School of Geography FACULTY OF ENVIRONMENT Working with Tables 1

2 Viewing Attribute Data attribute data are organised in database tables ArcMap Right click a data layer in the data frame Open Attribute Table OR create a report or graph ArcCatalog Click on a layer and preview the table 2

3 Table Window Rows (Records) + Columns (Fields) Features or standalone table Dynamic contents – move fields, change fonts, freeze Columns (Fields) Rows (Records) Unique ID 3

4 Tabular Data Field Types Different field types store different kinds of values Choose the right field type for the right value Field types vary according to table format Text, date, short, long, BLOB (graphics), double CNTRY_NAME: Russia – text POP_CNTRY: 151,827,600 – long COLOR_MAP: 3 – short SHAPE_AREA: 321294461992.126 – double Layer Properties Field tab 4

5 Navigating Tables Show All or Show Selected features Highlight records within show selected view Show selected and show all views Navigate rows 5

6 Table Window Menus Menus for row, columns and cells – right-click 6

7 Options Menu Options menu is drop down 7

8 Row Context Menu - Identify 8

9 ArcToolbox Access this through the ArcToolbox icon: Contains a variety of geoprocessing tools Functions in ArcToolbox can sometimes be carried out in context menus (right- clicking) Extensions will also appear Will be looking at some of the Analysis Tools tomorrow 9

10 Creating A New Field Suppose you want to calculate a value in a table based on existing data Need to add a new field Can add a field through the Data Management Tool Can add a new field through the Options menu in the table 10

11 Calculations in a New Field Can do this either through ArcToolbox or the Column Context Menu (right-click on column name) Both present you with a Field Calculator Can also delete the field if you are not happy with it = permanent! 11

12 Editing Data in the Table Enable the Editing Toolbar (View Toolbars Editor) Open the attribute table you want to edit Start Editing – headings of the table will go white Make changes Stop Editing and choose whether you want to save 12

13 Working with Tables Hands-on Exercise #5 13

14 Basic Statistics on a Field You can generate basic statistics on any field in the table Click on the name and right-click to select Statistics Does NOT work on text fields 14

15 Statistics Summary Can move between fields using the drop down box Will only see fields that are numerical 15

16 Statistics on a Selection 16

17 Summarise by a Field Might want to sum up occurrences of an event in an area Might want to find out the min or max value of an event in an area E.g. summarise the number of pupils by LEA 17

18 Calculations with Tables Hands-on Exercise #6 18

19 Mapping Spatial Data from External Sources Added by user with editing tools (tomorrow) Postcode data convert to Easting, Northing Data from a GPS receiver Depends on the GPS, e.g. the GPS might come with a facility to export a route to a shapefile Excellent source of information: 19

20 Bringing Data into ArcMap Can load Excel files directly into ArcGIS Use the Add Data button and select the sheet where the data are located (sheets are given a $) Excel files are read only and can only be viewed Need to conform to basic conventions: One header line No spaces in header names Do not start headers with a number Dont format cells as % KISS principle One Line Header No extra data over here 20

21 How to Map the Data - Points Geocode your data – turn your postcodes into X,Y coordinates Put these values into Excel – two columns with a single header For version 9.1, create a.csv,.txt or.dbf file Create X,Y data for points Tools Add X,Y Data 21

22 Mapping Attribute Data from Another Table Target table (map) + Source table (which you want to map) Joins 1 to 1 Many to 1 Relates Above plus: 1 to Many + Many to Many Relationship Classes 22

23 Example of a Relational Database 23

24 Attribute Join Physical connection between two tables Appends the attributes of the two tables Assumes a 1-to-1 or many[target]-to-1 relationship 24

25 Attribute Join Options Keep all rows – defaults Keep only matching rows 25

26 Connecting Tables with Relates Defines relationship between two tables Tables remain independent Can also have 1-to-many and many-to-many relationships Make selection and then open related table Discovers any related rows 26

27 Relate vs Relationship Class Relate Across different database tables Created on the fly in ArcMap, saved in.MXD and.LYR files Relationship Class (managed by the geodatabase) Permanent relate Within the same geodatabase Only exists in a geodatabase 27

28 Steps on How to Map the Data Join the data to a map file so that you can plot it Create the file in Excel (and export to.dbf,.csv or.txt if 9.1) Follow these basic rules: Have a single line header, one name per column Avoid spaces or strange characters in the header line Avoid formatting as percentages Avoid having any extra data outside of the rows and columns of your data Avoid starting headings with a number 28

29 Steps on How to Map the Data In ArcMap, open the file to which you want to add the data You can open the.dbf/.csv/.txt file in ArcMap or browse Right-click on the layer Joins and Relates Choose the column for joining on from the map file that matches the one in the.dbf/.csv/.txt file Select or browse for the.dbf/.csv/.txt file Select the column in the.dbf/.csv/.txt file that is in common with the map file and then join Save the map if you want the join to become permanent (right-click Data Export Data) 29

30 Troubleshooting values – can occur if there are features in the map that did not occur in your.dbf/.csv/.txt file – become 0 when join is made permanent values across the board – join was not successful Check that you have chosen the correct columns on which to do the join Make sure there are no spaces in the name/ids in one column but not the other (hidden spaces) 30

31 Bringing Data into ArcMap Hands-on Exercise #7 31

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