GIS DATA GIS DATA SOURCESSOURCES

Getting maps into Getting maps into the Computerthe Computer

Adding Data from Adding Data from existing tablesexisting tables

Tables....Tables....

The ‘data base’ part of GIS as a The ‘data base’ part of GIS as a relational database management relational database management systemsystem

A spreadsheet is how most people A spreadsheet is how most people see a table... And indeed Excel (the see a table... And indeed Excel (the most common spreadsheet program) most common spreadsheet program) can easily provide data to the ArcGIS can easily provide data to the ArcGIS or ArcViewor ArcView

Sample of tabular data...the database for a TIGER roads file

Combining tabular data with Combining tabular data with Spatial DataSpatial Data

There are incredible amounts of attribute There are incredible amounts of attribute data available in digital format.data available in digital format.

Virtually any tabular data can be used in Virtually any tabular data can be used in conjunction with the GIS.conjunction with the GIS.

Some sort of spatial ‘hook’ is required:Some sort of spatial ‘hook’ is required:- a street address- a street address- XY coordinates (Lat/Long)- XY coordinates (Lat/Long) - a country/state/county/tract identification- a country/state/county/tract identification

Many data sets are not developed to be Many data sets are not developed to be ‘spatial’… but the spatial component can be ‘spatial’… but the spatial component can be very enlightening….very enlightening….

A classic example of spatial patterns derived from data that is commonly considered “non-spatial”

http://www.usatoday.com/news/vote2000/cbc/map.htm

2004 Election Results

http://www.usatoday.com/news/politicselections/vote2004/countymap.htm

Even years later, the RED-BLUE designations persist in the American political lexicon

Red or Blue—Which Are You?Red or Blue—Which Are You?By Anne E. Kornblut, Slate Magazine 2004By Anne E. Kornblut, Slate Magazine 2004

““... Red and blue are states of mind, ... Red and blue are states of mind, not actual states. ... It's not as simple not actual states. ... It's not as simple as liberal vs. conservative, elite vs. as liberal vs. conservative, elite vs. populist, urban vs. rural, religious vs. populist, urban vs. rural, religious vs. nonreligious, educated vs. nonreligious, educated vs. uneducated, rich vs. poor—if it were, uneducated, rich vs. poor—if it were, the terms "red" and "blue" wouldn't the terms "red" and "blue" wouldn't have taken off as the have taken off as the best shorthand best shorthand for a divided Americafor a divided America....”....”

http://slate.msn.com/id/2103764/http://slate.msn.com/id/2103764/

Sources of Data …Sources of Data …

Virtually endless… even if the data Virtually endless… even if the data are not ‘available’ in digital form… are not ‘available’ in digital form… the use of copy/paste can be used to the use of copy/paste can be used to grab the data…grab the data…

US Census US Census (virtually everything about the US (virtually everything about the US population!)population!)

USDA USDA (Agricultural stats for the US)(Agricultural stats for the US)

UN-FAO UN-FAO (forestry/agriculture/population)(forestry/agriculture/population)

U.S. Census Bureau U.S. Census Bureau http://www.census.gov/main/www/cen2000.htmlhttp://www.census.gov/main/www/cen2000.html

(can be a difficult site to navigate)(can be a difficult site to navigate)

http://apps.fao.org/default.htm

Problems?Problems?

Often the data are of a different ‘type’: Often the data are of a different ‘type’: while the join tool in Arcview is fairly while the join tool in Arcview is fairly robust, the items to be joined must be robust, the items to be joined must be of the same type. e.g. number vs. text of the same type. e.g. number vs. text items. items.

Number items are Number items are rightright justified, text justified, text items are items are leftleft justified. Even though a justified. Even though a ‘number’ can appear as 2034, it may ‘number’ can appear as 2034, it may be a ‘text string’ rather than a number.be a ‘text string’ rather than a number.

Number items

Same field as ‘text’

Fixing the mixed type problem:Fixing the mixed type problem:

Within a spreadsheet program, such Within a spreadsheet program, such as Excel, convert the data typeas Excel, convert the data type

Within Arcview, add a new field to a Within Arcview, add a new field to a table and use the ‘calculate’ function table and use the ‘calculate’ function to convert to a number field.to convert to a number field.

In Arcview, add a new field. ‘calculate’ that field to be the old field with using an operator that converts the text string to a number field.

Note: the field type can be number or a character string

IF you need decimal places, specify them here,

the default value is 0

ArcGIS Field typesArcGIS Field types

Creating ‘new’ data in a tableCreating ‘new’ data in a table

ArcGIS (and Arcview) can be used to ArcGIS (and Arcview) can be used to manipulate the data in a table to manipulate the data in a table to create ‘new’ data relationshipscreate ‘new’ data relationships

e.g. population changee.g. population change

If asked to calculate the change in If asked to calculate the change in population, it is fairly simple to add a population, it is fairly simple to add a new field and calculate the value for new field and calculate the value for this ‘new’ informationthis ‘new’ information

Under the options pulldown you will find the option to create a new data field

Name the new field and choose its properties

Make sure the field is long enough to store the data...

For example: You cannot go back and change a text field that you set to hold 6 characters to change and hold ‘MISSISSIPPI’

Right click on the name of the new field, choose calculate new values.

The field will equal whatever expression you create in the box

In this example, I have calculated the % population change between 1990 and 1999

Make sure the number of () is correct for the expression

And the map based on these ‘new’ data...

To review :

calculating a field value....

The ADVANCED Button allows you to enter a VB (visual basic)

expression

Cardinality: these relationships allow data tables to be joined (a single table is created)

One to many: this situation requires a relate rather than joining tables. When tables are related, the related items of a selected item (in another table) are highlighted (the tables remain separate)

XY ‘events’...Data from the GPSXY ‘events’...Data from the GPS Adding x,y coordinate data to a mapAdding x,y coordinate data to a map

Click the Click the Tools menuTools menu and click and click Add XY DataAdd XY Data. . Click the table dropdown arrow and click a table that Click the table dropdown arrow and click a table that

contains x,y coordinate data. If the table is not on the map, contains x,y coordinate data. If the table is not on the map, click the Browse button to access it from disk. click the Browse button to access it from disk.

Click the X Field dropdown arrow and click the field Click the X Field dropdown arrow and click the field containing x-coordinate values. containing x-coordinate values.

Click the Y Field dropdown arrow and click the field Click the Y Field dropdown arrow and click the field containing y-coordinate values. containing y-coordinate values.

Click Edit to define the coordinate system and units Click Edit to define the coordinate system and units represented in the x and y fields. represented in the x and y fields.

The x,y coordinates will be automatically transformed to The x,y coordinates will be automatically transformed to match the coordinate system of the data frame. match the coordinate system of the data frame.

TipTip To add x,y data, your coordinates need to be in the To add x,y data, your coordinates need to be in the

projected units or decimal degrees. projected units or decimal degrees.

Getting GPS data into the GIS..... My favorite tool works with Garmin GPS devices . It is a free tool developed by the Minnesota Dept. of Natural Resources.http://www.dnr.state.mn.us/mis/gis/tools/arcview/extensions/DNRGarmin/DNRGarmin.html

It is an Arcview extension, that has a standalone VB program that will allow you to download the data from a Garmin GPS to a table format.