GIS 1 GIS Lecture 4 Geodatabases Copyright – Kristen S. Kurland, Carnegie Mellon University

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GIS Lecture 4Geodatabases

Copyright – Kristen S. Kurland, Carnegie Mellon University

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Outline

•Administrative Data Example•Data Tables•Data Joins•Common Datasets•Spatial Joins•ArcCatalog Overview•Geodatabases•Editing Tables•Excel Tips


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Administrative Data Example

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Administrative Data

Mission • What does the organization do?• Transaction event (who, what, where, when)-must have spatial component

What data is available? • Databases• Spreadsheets


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Example

County Property Assessments•Assesses the value of each land parcel and its structures

•Sets a property tax rate•Sends property tax bill = assessed value * tax rate


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Allegheny County Assessment WEB Site

http://www.county.allegheny.pa.us


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Westmoreland County Assessment WEB Site

http://207.140.67.68/westmoreland/viewer.htm


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Data Tables

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Property Table

Property Data• Owner• Address• Sale Date and Price• Map Lot Block Number


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Parcels GIS Layer

• Smallest geographic element is a deeded land parcel


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Data Joins

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Join Property Table to Parcels•Join on common attribute value•Values must be the same


Must remove dashes!

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Import Property Table to ArcMap

•Save Excel file as a comma separated file .CSV File or DBF (DBASE IV) file


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Add Table as Data Layer


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Join Table to Map•A common field joins or links tables•Records with the same value are matched•Some cleaning necessary (dashes removed)


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Join Table to Parcels


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Resultant Parcels Table•Property fields are appended to parcels table•Source files remain separate•Joins can be removed•Maps can be created from values in the new fields


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Resulting Assessment Map

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Resulting Assessment Map


Central Oakland Land Parcels

2003 Assessment

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Problems with Joins

•Saving .DBF and .CSV files in Excel•Avoid special formats•Keep it simple•Use Access as a “middle man”

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Common Datasets

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Common Datasets U.S. Census Maps and U.S. Census Tables


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Common Datasets•Zip Codes-Use with U.S. Census data or Geocoding


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Place Geocodes: FIPS Codes

Federal Information Processing Standards Codes

Developed by the National Institute of Standards and Technology

Codes for Place Names Throughout the World•countries•states/provinces•counties•metropolitan statistical areas (MSA’s)•cities•places - indian reservations, airports, and post offices in the US


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Place Geocodes: Hierarchy

Country: US

FIPS CODES

County: 003 (Allegheny)

State: 42 (Pennsylvania)

Tract: 0501

Block: 12 (US420030501312)

Block Group: 3CENSUS CODES

Minor Civil Division: 85188 (Wilkinsburg)

Parcel (Block & Lot#)


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Locating Data

•Contact agencies•Obtain data on-line


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Spatial Joins

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Spatial Joins•Spatially count points within polygons•Join tables using Shape field•Join points to polygons or polygons to points

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Spatial Joins•Join municipality name to points spatially


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Spatial Joins•Resultant point layer (food points) now contains municipality information


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Aggregate Data

• Summarize on spatial join- Counts the number of points (records) for each

municipality


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Aggregate Data

• Resultant Table- Count of points (food stores) in each polygon

(municipality)


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Join Summary Table• Join summary table of counts (based on municipality name from sum table) back to municipalities for labeling


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Label Counts•Label the count of stores from the summary join


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Label Counts•Show counts as a Choropleth Map


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Map with Points


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Map without Points


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ArcCatalog

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ArcCatalog


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Metadata


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Metadata


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Metadata


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Metadata


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Metadata


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Geodatabases

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Geodatabase

•‘geographic database’ •represents geographic features and attributes as objects and is hosted inside a relational database management system

•managing your coverages, grids, and shapefiles inside a database management system, or DBMS


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Enterprise Geodatabases

•require a ‘host’ DBMS -SQL Server, Oracle, or IBM DB2


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Personal Geodatabases

•based on the Microsoft JET engine -appear as an .mdb file (Microsoft’s JET engine is also used by Microsoft Access).


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Geodatabase Advantages

•Provide a uniform and IT compliant repository for geographic data.

•Many users can edit geographic data simultaneously.


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Geodatabases


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Importing Shapefiles into Geodatabases


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Importing Tables into Geodatabases


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dBASE and Tables

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dBASE Tables


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Editing Tables•Field definitions edited in ArcCatalog•Layers cannot be in use elsewhere

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Calculator Functions


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Calculator Functions


• Not just for numeric fields

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Excel Tips and Tricks

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FIPS Code Reminder

Country: US

FIPS CODES

County: 003 (Allegheny)

State: 42 (Pennsylvania)

Tract: 0501

Block: 12 (US420030501312)

Block Group: 3CENSUS CODES

Minor Civil Division: 85188 (Wilkinsburg)

Parcel (Block & Lot#)


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Formatting and Replace

•Delete any Excel formatting (e.g. borders, patterns, etc.)

•Delete unwanted text (e.g. word “tract”)-Find and replace

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Transpose Data

•Transpose data-Some census data saves data as rows instead of columns

-You need transpose the data so that tracts will be a column-Select your data in excel and go to Edit menu and select copy-Click on a cell outside of your selected data and go to edit menu to select paste special…

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Now you see the data transposed in the right way. All you need to do is to delete the original rows and save your file.

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Concatenate Strings

Sometimes you need add certain string before or after a value, and sometimes you want to combine two values. The excel CONCATENATE function makes that happen for you.

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If you have the below dataset, and want to combine the state ID and county ID together as another variable and you want to make sure the new StateCountyID has the length of 5

For example, you want to add a “0” to State IDs that are only 1 character long, and you want add “00” to county IDs that that is 1 character long and “0” to those that are 2 characters.

Concatenate Strings

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Start by adding a new column right to StateID, and enter:

=IF(LEN(A2)=1,CONCATENATE(0,A2),A2)

What you tell excel is: if the length of the cell A2 is 1, add 0 before the original value, otherwise, keep the original value

Concatenate Strings

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After that, you copy and paste the formula to the rest of the column, and you will see the following result

Concatenate Strings

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Now let’s solve the problem for county ID. In the cell next to C2, you enter:

=IF(LEN(C2)=1,CONCATENATE("00",C2),IF(LEN(C2)=2,CONCATENATE("0",C2),C2))

What this tells excel is if the length of county ID is 1, add “00” before it, if the length is 2, add “0” before it, if the length is 3, keep the original

Concatenate Strings

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Now you copy and paste the formula to the rest of the column and you get the above result

Concatenate Strings

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Next, you create a new column called StateCountyID, and enter is the cell E2:

=concatenate(B2,D2)

By this, you are telling Excel to combine the two new columns that you created in the previous steps

Concatenate Strings

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Now you just need to copy and paste the formula to the rest of the column and you finally get what you want.

Concatenate Strings

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Mid Function

Sometimes, a simple replace won’t do for you to substring a column. In this case, you can use Excel’s mid function to get a subset of a value.For example, if you have the following data want extract two letters in the middle, say 12 from the first row, and 13 from the second row, and so on, the Excel MID function is your choice.

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Mid Function

You enter: =mid(A1,4,2) in the cell next to A1. What you tell excel to do is: From cell A1, extract 2 characters starting from the 4th character from left.

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Mid Function

Then you copy and paste the formula from B1 to the rest of the column and you get what you need.

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Excel Tips and Tricks

•Formatting•Find and Replace•Transpose•MID Function•Concatenate


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Other Excel Functions

You might want to learn some other excel functions that could help you clean the data, such as:• Right()• Left()• Exact()


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Conclusion

•Administrative Data Example•Data Tables•Data Joins•Common Datasets•Spatial Joins•ArcCatalog Overview•Geodatabases•Editing Tables•Excel Tips


Documents

GIS 1 GIS Lecture 4 Geodatabases Copyright – Kristen S. Kurland, Carnegie Mellon University