ATLAS*GIS and METAPONTO Exercise 2

These materials were developed by Shannon Crum and Kenneth E. Foote, Department of Geography, University of Texas at Austin, 1994. These materials may be used for study, research, and education in not-for-profit applications. If you link to or cite these materials, please credit the authors, Shannon Crum and Kenneth E. Foote, The Geographer's Craft Project, Department of Geography, The University of Colorado at Boulder. These materials may not be copied to or issued from another Web server without the authors' express permission. Copyright 1994. All commercial rights are reserved. If you have comments or suggestions, please contact the authors or Kenneth E. Foote at k.foote@colorado.edu.


This page is available in a framed version.  For convenience, a Full Table of Contents is provided.

Introduction

In this exercise you will continue with your analysis of the Metaponto dataset. Since AtlasGIS continually updates the Geo files, you might want to start with a new floppy and freshly unzipped Metaponto files. To begin, start Atlas GIS and load both your Geo files and Attribute tables from your diskette. These are the LAGO files. Load using File | Open. When loading the Attribute table, indicate that you want to link the table to the Allsites layer of the Geo file. Note: Please take a look at the last page of this exercise first. The "What to hand in" section may influence your approach to it.

1. Creating Additional Attribute Data Fields

Let's say you would like to create a new variable so that you can recode some of the information in the Attribute table. In this case, you would like to create a variable called PHASE that will recode the fifteen AGE codes to five PHASE codes for further analysis.

Choose Table | Define Columns. Hint: This command is also available on the Button Bar. This will open the Tables dialog box, where you only have one table linked to Geo file by the Allsites layer. Selecting this will open the Define Columns dialog box, wherein a spreadsheet appears showing the present database structure. Here, the columns of your database are the rows on the left hand side. Examine the various columns. While a new column can be added anywhere in the spreadsheet using the Insert button to the right of the dialog box, this time you will use the mouse to move to the last column (row) at the bottom of the spreadsheet. AtlasGIS has already started the column, you need to provide a name and alter the other information, as necessary. Now, to define a column for PHASE, fill in the fields as follows:

Note: Clicking on the Type field will bring up a list of options. The above settings create a new column in the Attribute table named PHASE, which will contain a single one-digit number. No decimal points will be included. The number will be visible in the Attribute table, and will be anchored so that it always appears on the screen no matter where you scroll in the spreadsheet. The width specifies the number of columns Atlas*GIS will use to display the variable in the table. Seven columns will permit us to read the variable name, PHASE, with space to spare. The description will appear on the top left of the screen when the data field is highlighted.

Click on OK when finished with this form. When asked whether to restructure the database, click on OK. Choose Window | New Table Window , then in the Window Layer dialog box, select Allsites to see the new field. Hint: Button Bar. Your new field will appear as a new column heading without data below it.

2. Recoding Data by Expression

After creating a column in the spreadsheet for a new variable, you will wish to fill it with new values, by row, for each site. In this case, AtlasGIS can do the dirty work for you by using a mathematical expression. Go to Table | Calculate Column. A Calculate Column dialog box appears. Fill this in as follows: When you select the Expression field, the Expression Builder dialog box appears. You have used this before to select variable type. Now, you can select from the listings of Functions and Operators to help insert the above expression. Some of the expression must be typed in. The whole expression may be typed in, but be careful about the spaces. This version of the software is sensitive to them, and the expression builder properly inserts them. When you are finished, you can click on the Verify button to have the program check to see if it is a valid expression.

Click OK when you are finished. IIF is a "function" that evaluates an "expression" (in this case AGE=l). If the expression is true, Atlas*GIS places the value "1" in the new column of the spreadsheet under PHASE. If the expression is false, Atlas*GIS keeps the original value of PHASE in the column.

You have recoded only one value of AGE. Now you must repeat the previous step four more times, each time with a different IIF statement. Again, go to Table | Calculate Column. This time, fill this in as follows:

This expression can be read as follows: "if the value of AGE is greater than 1 and less than 7 (i.e. 2-6) then make the variable PHASE=2, otherwise leave the value of PHASE unchanged." Click OK.

Now, repeat this step for each of the following expressions to complete the remainder of the recoding: IIF(AGE > 6 .AND. AGE < 11,3,PHASE), IIF(AGE > 10 .AND. AGE < 15,4,PHASE), and IIF(AGE = 15,5,PHASE).

3. Creating a Thematic Map of PHASE

Now you will create a thematic map of PHASE using the steps outlined in the previous Metaponto exercise. Indeed, this new map should be identical to the one you plotted for the last exercise. When you go into the Map | Layers and Themes menus, choose Allsites as the layer, PHASE as the variable expression. You will want to use the Ranged Symbol method of symbolization with a "List of Values" and five categories. Pick symbol styles so that pre-Greek and post-Greek settlements use the same color by different symbols, and so the three phases of Greek settlement use the same symbol, but in three different colors.

4. Examining Tombs by PHASE

Now that we have recoded AGE into the PHASE variable, let's consider the number and distribution of tombs by this new variable. Let's go about this analysis in three steps, one for each phase of Greek settlement. We'll ignore pre- Greek and post-Greek periods.

First, Query | Select by Value. In the Select by Value dialog box that appears, highlight Allsites in the Layer subpanel, select the Replace Selected option in Selection Results subpanel, and select the By Expression option in the Select subpanel. Click on Expression in the subpanel and the Expression Builder dialog box appears. Specify: PHASE = 2 .AND. TYPE = 2. This condition will search for tombs (TYPE=2) in the first period of Greek settlement (PHASE=2). Click on OK, then click OK again to leave the Expression Builder. Click on OK one more time to see the highlighted results.

Once you have examined this map, click outside the map area to clear your selections. (You don't want these selections to interfere with your subsequent searches.)

Second, Query | Select by Value. Select Allsites as the layer, but this time specify the Expression as: PHASE = 3 .AND. TYPE = 2. Examine the results.

Once you have examined this map, deselect the features.

Third, Query | Select by Value. Select Allsite as the layer, but specify the Expression as: PHASE = 4 .AND. TYPE = 2. Examine the results.

Is there a trend in the number of tombs by settlement phase? After you have considered this issue, deselect the features.

5. PHASE and TYPE: A Bivariate Relationship

Let's use Atlas*GIS to consider a couple of bivariate relationships, first between PHASE and TYPE. That is, we wish to examine the relationship between settlement phase and the distribution of farms and tombs.

Choose Map | Layers and Themes. Make sure that the Allsites layer is chosen, and the Theme option is selected. This time, however, click on the Two Variable box to turn it On. For Variable 1, click on Expression and choose PHASE as the variable, and select Ranged Symbol as Map Type. For the Variable 2, pick TYPE as the variable, and Ranged Symbol as the Map Type.

In the Variable 1 subpanel, click on Ranges. In the Ranged Symbol subpanel, specify the method as List of Values and 5 as the Number of Ranges. Then, Calculate. Move down to the spreadsheet and edit the Values to 1, 2, 3, 4, 5, respectively, for the five Ranges of PHASE. After Calculate, click on OK. We wish to ignore pre-Greek and post-Greek sites. Do this by indicating the Blank symbol for a pattern for both pre-Greek and post-Greek sites, then assign a different symbol shape to each of the three phases of Greek settlement (Values 2, 3, 4), say an open triangle, an open circle, and an open square. After clicking OK, click on the Ranges button in the Variable 2 subpanel.

In regard to the Ranging Method, for TYPE you should specify List of Values and 5 for the Number of Ranges. Calculate, then move down to the spreadsheet to edit the Values menu to 0, 1, 2, 3, 4. We wish to ignore all sites that aren't either farms (TYPE=1) or tombs (TYPE=2). Do this by choosing the Clear color, which is the box with an X in the Color Dialog box, for the 0, 3, 4, Out of Range, and Missing ranges. For farms (value 1), choose red as the color. For tombs (value 2), choose black as the color. Use 10 as the symbol size for both farms and tombs. Now, go back and view your map.

Remember, you'll have to edit the page elements to produce an acceptable map. Remember the steps you used in Exercise 1 to move, resize, and edit page elements. Be sure to turn on the Thematic Legend-2 (and turn off the Layer Legend) and edit the Thematic-Legend-2 (including the legend descriptions).

Interpret the map. What does it demonstrate about the relationship of farms and tombs during the three phases of Greek settlement? If you can improve the readability of the symbols, go back to the previous menus and make adjustments of shape, size, and color.

Create a Project file here so that you can return to this step later for further work and for plotting the map.

6. PHASE and ELEV (Elevation): Another Bivariate Relationship

Now consider the relationship between PHASE and site elevation (ELEV) in the same way. We are interested with whether the farms moved up-slope or downslope during the three phases of Greek settlement. Use the same procedure for creating a bivariate map that you used in the previous step. For PHASE you can use the same settings you employed in the previous map. However, for the Ranging Method of the ELEV variable, use Continuous and 2 Number of Ranges. Set 0 and 88 as the Min and Max values for Range 1. Set 89 and 122 as the Min and Max values for Range 2. These values are taken from the Statistics subpanel. The Maximum Elevation of a site in the Allsites layer is 122 and the Average Elevation is 87.69, which we are using as a breakpoint between the two ranges.

Remember, you'll have to edit the map elements to produce an acceptable map. Remember the steps you used in Exercise 1 to move, resize, and edit map elements. Be sure to turn on the Thematic Legend-2 (and turn off the Layer Legend) and edit the Thematic-Legend-2 (including the legend descriptions).

Create a Project file here so that you can return to this step later for further work and for plotting the map.

7. Creating New Layers by PHASE

Now let's create separate map layers for sites of each PHASE. That is, let's divide the sites recorded in the Allsites layer by PHASE and then copy them into three separate layers for further independent analysis. In this procedure, a separate database table will also be created and attached their respective layers for following steps in this exercise.

First, Query | Select by Value. In the Select by Value subpanel, pick Allsites as the layer, By Value in the Selectsubpanel, and Replace Selected in the Selection Results subpanel. Then, select PHASE as the Column and 2 as the Value. When you are finished, highlighted on the map are all the sites of PHASE=2.

Now let's copy them to their own layer, to be called PHASE2. Go to Map | Combine | By Value. In the Combine By Value dialog box, under the Combine Feature From subpanel, choose Allsites as the Layer and ID as the Grouping Expression. Turn the Combine Non-Touching button Off and the Use Selected button On. In the Copy Results To subpanel, hit on the New Layer button. Select Point for Layer Type, Lago.agf for the File Name, then enter PHASE2 for the name of the New Layer, and Phase 2 sites for the Layer Description. Click on OK. Then click on OK again. A warning will appear stating "The Output Layer has no Database Table", at which time you should just click on OK. When this step is finished processing, you won't see a change on the screen since the newly copied features are right on top of their counterparts in the Allsites layer, but you can change this later.

Now, you will remedy the warning you just received. Each layer in a map can have a database table attached to it and, up to this point, only the Allsites layer has one. Using the Query and Map | Combine commands creates a subset of the geographic elements, which were copied to another layer, but during this process a subset of the database table was also created. Now, you will save this subset down as a separate database table and attach it to the PHASE2 layer. Go to File | Save As. When the Save As dialog box appears, make sure the A: drive is selected and the File To Save is set to the LAGO.dbf. This may be somewhat confusing, but you are not going to save this down to the LAGO.dbf, you will save it as PHASE2.dbf which you will indicate under File Name. Set the Selected Features or Rows Only to On and Use New File to Off. Click on OK. Now, go to File | Open and select PHASE2.dbf, which will bring up the Table Link dialog box. Choose Links To Geo, PHASE2 as the layer, and ID as the Key Column. Click on OK.

Second, repeat the procedure for PHASE 3 sites. Query | Select by Value. In the Select by Value subpanel, pick Allsites as the layer, By Value in the Select subpanel, and Replace Selected in the Selection Results subpanel. Then, select PHASE as the Column and 3 as the Value. When you are finished, displayed on the screen are all the sites of PHASE=3.

Copy them to their own layer, to be called PHASE3. Go to Map | Combine | By Value. In the Combine By Value dialog box, under the Combine Feature From subpanel, choose Allsites as the Layer and ID as the Grouping Expression. Turn the Combine Non-Touching button Off and the Use Selected button On. In the Copy Results To subpanel, hit on the New Layer button. Select Point for Layer Type, Lago.agf for the File Name, then enter PHASE3 for the name of the New Layer, and Phase 3 sites for the Layer Description. Click on OK. Then click on OK again. A warning will appear stating "The Output Layer has no Database Table", click on OK.

Again, you will save down the subset of the database table and attach it to the PHASE3 layer. Go to File | Save As. When the Save As dialog box appears, make sure the A: drive is selected and the File To Save is set to the LAGO.dbf. This may be somewhat confusing, but you are not going to save this down to the LAGO.dbf, you will save it as PHASE3.dbf which you will indicate under File Name. Set the Selected Features or Rows Only to On and Use New File to Off. Click on OK. Now, go to File | Open and select PHASE3.dbf, which will bring up the Table Link dialog box. Choose Links To Geo, PHASE3 as the layer, and ID as the Key Column. Click on OK.

Third, repeat the procedure for PHASE 4 sites. Query | Select by Value. In the Select by Value subpanel, pick Allsites as the layer, By Value in the Select subpanel, and Replace Selected in the Selection Results subpanel. Then, select PHASE as the Column and 4 as the Value. When you are finished, displayed on the screen are all the sites of PHASE=4.

Now let's copy them to their own layer, to be called PHASE4. Go to Map | Combine | By Value. In the Combine By Value dialog box, under the Combine Feature From subpanel, choose Allsites as the Layer and ID as the Grouping Expression. Turn the Combine Non-Touching button Off and the Use Selected button On. In the Copy Results To subpanel, hit on the New Layer button. Select Point for Layer Type, Lago.agf for the File Name, then enter Phase4 for the name of the New Layer, and Phase 4 sites for the Layer Description. Click on OK. Then click on OK again. A warning will appear stating "The Output Layer has no Database Table", click on OK.

Finally, save the subset down as a separate database table and attach it to the PHASE4 layer. Go to File | Save As. When the Save As dialog box appears, make sure the A: drive is selected and the File To Save is set to the LAGO.dbf. This may be somewhat confusing, but you are not going to save this down to the LAGO.dbf, you will save it as PHASE4.dbf which you will indicate under File Name. Set the Selected Features or Rows Only to On and Use New File to Off. then click on OK. Now, go to File | Open and select PHASE4.dbf, which will bring up the Table Link dialog box. Choose Links To Geo, PHASE4 as the layer, and ID as the Key Column. Click on OK.

You have now created three new layers in your geographic file with their own separate database tables. You can't see them well since they overlay the Allsites features. Go to Map | Layers & Themes and turn "Off' Allsites. Then turn "On" each of the new layers one at the time and return to the map after each change to see what each layer looks like. Use the Window | New Table Window command to see the individual database tables.

8. Proximity to Streams by PHASE

Now that we have separated the sites by PHASE, we wish to consider their proximity to streams in the three periods of Greek settlement. That is, through time, were the sites established closer or further away from the streams? There may or may not be any significant relationship between streams and settlement locations at the time when these settlements were occupied. The tools used in this part of the exercise, however, could be used to examine all sorts of proximity relationships, such as the numbers of sites within some distance of sites presumed to be economically, politically, or religiously important. Again, we will move through this analysis in three identical steps, one step for each phase.

First, let's consider this proximity relationship for PHASE=2. Go to Map | Layers & Themes and turn off Allsites, PHASE3, and PHASE4. Turn on PHASE2. Redraw. Then go to Query | Select by Location | Near. The Select by Location - Near dialog box appears. In the Select Features From subpanel, choose PHASE2. In the Selection Options subpanel, choose Select Features Closer Than and enter 100 meters, and turn Off the Use Distance to Region Centroid. In the Located Near Features From subpanel, select Streams and turn Off the Selected Features Only option and the Deselect When Done option. In the Selection Results subpanel, choose Replace Selected. OK. Note: If the entire map seems to have been selected, return to Query | Select by Location | Near and check to see if both the PHASE2 and Transect layers have been selected. If so, then click on the Transect layer to deselect it, then continue. To see the database information of the selected features, go to Window | New Statistics Window and select PHASE2. Record the Count information.

Now, Query | Select by Layer. Choose PHASE2 as the Layer Name. and select the Toggle option. Then click on OK. The "toggle" option inverts your selections for a given layer. The first map showed sites within 100 meters of streams. This second map shows sites beyond 100 meters of streams. Window | New Statistics Window to find out how many sites are beyond 100 meters of streams. Compare the numbers you have recorded for sites within 100 meters of streams to calculate the proportion of sites with 100 meters of streams.

Second, consider proximity in relationship to PHASE=3. Go to Map | Layers & Themes and turn off PHASE2. Turn on PHASE3. Redraw. Then go to Query | Select by Location | Near. The Select by Location - Near dialog box appears. In the Select Features From subpanel, choose PHASE3. In the Selection Options subpanel, choose Select Features Closer Than and enter 100 meters, and turn Off the Use Distance to Region Centroid. In the Located Near Features From subpanel, select Streams and turn Off the Selected Features Only option and the Deselect When Done option. In the Selection Results subpanel, choose Replace Selected. Redraw, if necessary. To see the database information of the selected features, go to Window | New Statistics Window and select PHASE3. This time instead of recording the information, click on the Freeze button. This will freeze this information, so that you may select other features and compare the information without writing it down.

Now, Query | Select by Layer. Choose PHASE3 as the Layer Name. and select the Toggle option, OK. Again, the first map showed sites within 100 meters of streams. This second map shows sites beyond 100 meters of streams. Window | New Statistics Window to find out how many sites are beyond 100 meters of streams. Compare the numbers with those for sites within 100 meters of streams to calculate the proportion of sites with 100 meters of streams.

Finally, consider proximity in relationship to PHASE=4. Go to Map | Layers & Themes and turn off PHASE3. Turn on PHASE4. Redraw. Query | Select by Location | Near. Choose PHASE4, 100 meters, Off, Streams, Off, Off, Replace Selected. Redraw, if necessary. Go to Window | New Statistics Window and select PHASE4. Click on the Freeze button.

Then, Query | Select by Layer. Choose PHASE4 as the Layer Name. and select the Toggle option, OK. Go to Window | New Statistics Window to find out how many sites are beyond 100 meters of streams. Compare the numbers with those for sites within 100 meters of streams to calculate the proportion of sites with 100 meters of streams.

9. Using Buffers to Measure Proximity to Division Lines

The division lines in your file may be the remains of a very early land survey system that may have been used by the settlers to align roads and plat farms. It would be interesting to investigate the association of division lines with the archeological finds by PHASE. This time we will use a different method to assess proximity, by means of "buffers" around the division lines. Two steps are involved in making a comparision of this kind: 1) create buffer zones adjacent to all division lines in the study area; and 2) use this zone to select sites in each PHASE layer.

To create the buffer, go to Map | Create Buffers. In the Create Buffer dialog box, use the following values:

Create Buffers Around Features In subpanel:

Buffer Options subpanel: Copy Buffers To subpanel: The New Layer dialog box will appear, then use the following values: Click on OK, then OK again.

The buffering operation takes a few moments. You have now created 100-meter wide zones around all division lines in the study area. The zones are stored in their own layer, which you created and named DBuffer5O. Now we want to use these zones to pick out sites that are close to division lines in each of the PHASE layers.

To accomplish this task for PHASE2, go to Map | Layers & Themes, turn off Allsites and turn on PHASE2. OK. Next, go to Query | Select by Location | Touching. This allows you to select features touching other features, in this case sites touched by the division line buffer zones. The settings in the dialog box should be set as follows:

Select Features From subpanel:

Select Options subpanel: Touching Features From subpanel: Selection Results subpanel: Click on OK. How many sites were selected?

Now Query | Select by Layer and specify PHASE2, then Toggle. Bring up a New Statistics Window to count the number of PHASE2 sites that are not touching the division line buffers. What is the proportion of touching to non-touching sites in PHASE2.

Note: If the entire map seems to have been selected, return to Query | Select by Location | Near and check to see if both the PHASE2 and Transect layers have been selected. If so, then click on the Transect layer to deselect it, then continue.

For PHASE3, go to Map | Layers & Legends, turn off PHASE2 and turn on PHASE3. Redraw. Go to Query | Select by Location | Touching. This allows you to select features touching other features, in this case sites touched by the division line buffer zones. The settings in the dialog box should be set as was done previously, except that you should indicate PHASE3 as the layer to Select Features From.

Again, Query | Select by Layer, specify PHASE3, then Toggle. Bring up a New Statistics Window to count the number of PHASE3 sites that are not touching the division line buffers. What is the proportion of touching to non-touching sites in PHASE3.

For PHASE4, go to Map | Layers & Legends, turn off PHASE3 and turn on PHASE4. Redraw. Go to Query | Select by Location | Touching. This allows you to select features touching other features, in this case sites touched by the division line buffer zones. The settings in the dialog box should be set as was done previously, except that you should indicate PHASE4 as the layer to Select Features From.

Again, Query | Select by Layer, specify PHASE4, then Toggle. Bring up a New Statistics Window to count the number of PHASE4 sites that are not touching the division line buffers. What is the proportion of touching to non-touching sites in PHASE4.

Does there appear to be a clear relationships between division lines and sites in any of the three periods of Greek settlement?

10. Tombs and Division Lines

Perhaps it would be better to refine the previous analysis. Considering the relationship of division lines to all archeological remains in the study area may be too coarse a method of analysis. Any possible relationship between, say, farms and division lines or tombs and division lines might be lost by including all TYPES of site in analysis.

Refine your analysis to consider the relationship between division lines and farms and division lines and tombs in the Allsites, PHASE2, PHASE3, and PHASE4 layers. Use the techniques previously introduced to develop your own analytical strategy.

11. Clean-up

Before you leave Atlas*GIS, always make sure you have created mapfiles as needed so you can return to the different parts of your work. Be sure to close your Geo and Attribute Table files.

12. What to Hand In

For this exercise, please hand in:

  1. A complete, plotted map of the relationship between PHASE and TYPE.
  2. A complete, plotted map of the relationship between ELEVATION and PHASE.
  3. A brief written analysis (which may include maps) of the relationships of PHASEand TYPE, ELEV and PHASE, and of the relationship of division lines to farms and tombs.


Last Revised 4/1/00.LNC.