Geography 476 Lab 3

Geography 476 - Lab 3
Overlay

Assigned - February 17/18, 2010
Due end of day February 24/25.
Deliverable instructions

Syllabus Lectures Labs Software
Reading:

Chrisman Ch5
Data flow diagrams with Dia

Learning objectives. After completing this lab and readings you should be able to:

Describe the characteristics of the geometry phase and attribute phase of overlay operations.
Export selected features to a new shapefile.
Overlay vector polygons (overlay, operations overview, union, intersect, identity)
Use raster calculator to overlay raster data
Summarize attribute fields
Create and apply boolean query equations to perform overlays.
Adjust the Spatial Analyst analysis environment settings to suit analysis needs.

Extra credit with data flow diagrams

Part 1: Session preparation

Use Windows Explorer to Tools menu > Map Network Drive Y: to \\oasis\gis
Verify that Z: is mapped to geo/classes
Enable Spatial Analyst and display the spatial analyst toolbar
Use Windows Explorer to create a new folder: Z:\Geog476\username\Lab3
Save your ArcMAP project as Z:\Geog476\username\Lab3\Lab3.mxd

Part 2: Data preparation - select and export:
Overlay operations on layers with many features take a very long time to process. It is good practice to limit the features for analysis to just the analysis region. Exporting selected features is an alternative to the clip operation and takes less time to process.

Add data:

Z:\Geog476-Materials\NWI\WI_wetlands.gdb\CONUS_wetlands
Y:\portage\shapefile\pc_soil_ssurgo.shp
Y:\portage\shapefile\pc_quads.shp

This is the metadata document for the fields in the SSURGO soils layer and related attribute tables. 'MUSYM' is a soil identification key field used to join the the related attribute tables to this base polygon layer.
Open the attribute table for CONUS_wet_poly and note how many features are in the layer. Close the table.
Open the 'Select by attributes' dialog: Selection menu > Select by attributes

Set the 'Layer' to 'pc_quads'
Enter this equation in the SELECT FROM WHERE window: "QUADNAME" = 'Rocky Run'. Correct use of double and single quotes is important in SQL expressions.
Click 'Ok'

The boundary for the Amherst quadrangle should be shown with a blue selection outline. If you open the attribute table you will see that the record for Rocky Run is selected in blue.
Open the ‘Select by Location’ dialog: Selection menu > Select by location

Check the boxes next to CONUS_wet_poly and pc_soil_ssurgo.shp
Also check ‘use selected features’ if it is not already; to the right it should indicate that there is one record selected in ctyppoly.
The dialog should look like this.
Click ‘Ok’

Export the selected records in CONUS_wet_poly and pc_soil_ssurgo.shp:

Right-click on CONUS_wet_poly > Data > Export data. Name the file Z:Geog476\username\Lab3\NWI_rockyrun.shp
Right-click on pc_soil_ssurgo.shp > Data > Export data. Name the file Z:Geog476\username\Lab3\ssurgo_rockyrun.shp

Question 1:Explain why the 'select by location' and 'export data' sequence is or is not an overlay operation? Consider the geometric and attribute phases of overlay to justify your answer.

Part 3: Intersect soils and wetlands:

Show the ArcToolbox window
Open the intersect dialog: ArcToolbox window > Analysis tools > Overlay > Intersect (double-click)

Select these layers to intersect.

Z:Geog476\username\Lab3\NWI_rockyrun.shp
Z:Geog476\username\Lab3\ssurgo_rockyrun.shp

Set the output file to be: Z:Geog476\username\Lab3\NWI_ssurgo.shp
The dialog should look like this. Click 'Ok'.
Add the data to the data frame when the operation is complete.

Calculate polygon area for NWI_ssurgo.shp:

Review Lab 2 Part 3 for instructions about how to add a field and calculate area.
Add field named 'ovl_area' type double precision 12 scale 6
Calculate the area in square meters.

Calculate the percentages of the soils in each wetland in NWI_ssurgo.shp.

Add field named 'pct_area' type double precision 12 scale 6
Right-click on 'pct_area' > Field calculator and enter this equation: [ovl_area]/([acres]* 4046.856)

Question 2: What are the units and level of measurement of the 'acres' field? What attribute operation(s) has been performed with [ovl_area]/([acres]* 4046.856)? Do the pct_area values represent an increase or decrease in information?
Summarize for the maximum single soil area of each watershed
Right-click on OBJECTID > Summarize
Open the pct_area and check 'Maximum'
Set the output table to Z:\Geog476\username\Lab3\pct_max_area.dbf
Click 'Ok'
Add the data to your project when prompted after the summary is complete.

Open the summary table. If you don't see it in the table of contents click the 'Source' tab at the bottom of the Table of Contents.
Question 3: What is the OBJECTID of the wetland(s) with the greatest number of soil types present? What SQL attribute query will select the records of wetlands located on only one soil type?

Join pct_max_area.dbf to the attribute table of NWI_ssurgo.shp using OBJECTID as the key field.
Question 4:Once the tables are joined what SQL equation will select the largest soil polygon/soil type in each wetland? Which measurement framework (Table 2-6) best describes the overlay analysis to measure this soil property of wetlands? Which attribute combination method (Table 5-1) best describes the attribute phase of this overlay?

Part 4: Line overlay points

Add data

Y:\portage\shapefile\pc_GreenCircle.shp
Y:\portage\shapefile\pc_roads.shp

Open the intersect dialog: ArcToolbox window > Analysis tools > Overlay > Intersect (double-click)
Use these parameters for the intersection.
Open the attribute table for pc_roads.shp and perform a Summarize operation on the field 'FID_pc_Gre' to measure the number of times roads cross each SEGMENT.
Question 5: What is the average number of road crossings on the Green Circle Trail's segments?

Part 5: Convert polygons to raster

Add data:

Z:\Geog476-Materials\SRTM\wi_srtm_500
Y:\wisconsin\dnr\orig_veg_cover\orig_veg_cover\orig_veg_cover.shp

Adjust the Spatial Analyst analysis environment options:
Open the options dialog: Spatial analyst toolbar button > Options
In the 'General' tab set the Working Directory to Z:\Geog476\username\Lab3. Spatial Analyst will write temporary output files to the working directory.
In the 'Extent' tab set the 'Analysis extent' to be the 'Same as layer wi_srtm_500'.
In the 'Cell size' tab set the 'Analysis cell size' to 'Same as layer wi_srtm_500'.
Click 'Ok'

Open the 'Polygon to raster' tool: ArcToolbox > Conversion tools > to Raster > Polygon to raster
Use these parameters to convert orig_veg_cover.shp to raster.
Inspect the output grid and compare it with the input polygons.
Question 6: Which measurement framework was applied to implement the conversion of polygons to raster cells? What is the output cell size?

Part 6: Combine land cover.

Open the Single Output Map Algebra dialog: ArcToolbox > Spatial Analyst tools > Map Algebra > Single Output Map Algebra
Read the ESRI help files on Combine and How combine works to better understand how the operation works and the nature of the output file
Use these parameters: COMBINE (Z:\Geog476\username\lab3_prep\orig_veg_500, Z:\Geog476-Materials\Crop_data\NASS_WI\cdl_awifs_r_wi_2008.tif)
Output file: Z:\Geog476\username\lab3_prep\combine_veg
Open the attribute table for combine_veg and sort the COUNT field in descending order.
Question 7: What attribute map combination method (Table 5-1) is applied with the combine operation?
Question 8: What are the five biggest area changes measured with the combine operation? This question is about change, not what has remained the same. Check the cdl_awifs_r_wi_2008.tif's attribute table for the meaning of the cell values there. The metadata for orig_veg_cover has definitions of the land type categories.
Question 9: What are the cell sizes for each input grid and the output grid? How might this difference affect the output from the combine operation?

Version of Feb 17, 2010

Geography 476 - Lab 3 Overlay Assigned - February 17/18, 2010 Due end of day February 24/25. Deliverable instructions	Syllabus Lectures Labs Software Reading: Chrisman Ch5 Data flow diagrams with Dia
Learning objectives. After completing this lab and readings you should be able to: Describe the characteristics of the geometry phase and attribute phase of overlay operations. Export selected features to a new shapefile. Overlay vector polygons (overlay, operations overview, union, intersect, identity) Use raster calculator to overlay raster data Summarize attribute fields Create and apply boolean query equations to perform overlays. Adjust the Spatial Analyst analysis environment settings to suit analysis needs.
Extra credit with data flow diagrams
Part 1: Session preparation Use Windows Explorer to Tools menu > Map Network Drive Y: to \\oasis\gis Verify that Z: is mapped to geo/classes Enable Spatial Analyst and display the spatial analyst toolbar Use Windows Explorer to create a new folder: Z:\Geog476\username\Lab3 Save your ArcMAP project as Z:\Geog476\username\Lab3\Lab3.mxd
Part 2: Data preparation - select and export: Overlay operations on layers with many features take a very long time to process. It is good practice to limit the features for analysis to just the analysis region. Exporting selected features is an alternative to the clip operation and takes less time to process. Add data: Z:\Geog476-Materials\NWI\WI_wetlands.gdb\CONUS_wetlands Y:\portage\shapefile\pc_soil_ssurgo.shp Y:\portage\shapefile\pc_quads.shp This is the metadata document for the fields in the SSURGO soils layer and related attribute tables. 'MUSYM' is a soil identification key field used to join the the related attribute tables to this base polygon layer. Open the attribute table for CONUS_wet_poly and note how many features are in the layer. Close the table. Open the 'Select by attributes' dialog: Selection menu > Select by attributes Set the 'Layer' to 'pc_quads' Enter this equation in the SELECT FROM WHERE window: "QUADNAME" = 'Rocky Run'. Correct use of double and single quotes is important in SQL expressions. Click 'Ok' The boundary for the Amherst quadrangle should be shown with a blue selection outline. If you open the attribute table you will see that the record for Rocky Run is selected in blue. Open the ‘Select by Location’ dialog: Selection menu > Select by location Check the boxes next to CONUS_wet_poly and pc_soil_ssurgo.shp Also check ‘use selected features’ if it is not already; to the right it should indicate that there is one record selected in ctyppoly. The dialog should look like this. Click ‘Ok’ Export the selected records in CONUS_wet_poly and pc_soil_ssurgo.shp: Right-click on CONUS_wet_poly > Data > Export data. Name the file Z:Geog476\username\Lab3\NWI_rockyrun.shp Right-click on pc_soil_ssurgo.shp > Data > Export data. Name the file Z:Geog476\username\Lab3\ssurgo_rockyrun.shp Question 1:Explain why the 'select by location' and 'export data' sequence is or is not an overlay operation? Consider the geometric and attribute phases of overlay to justify your answer.
Part 3: Intersect soils and wetlands: Show the ArcToolbox window Open the intersect dialog: ArcToolbox window > Analysis tools > Overlay > Intersect (double-click) Select these layers to intersect. Z:Geog476\username\Lab3\NWI_rockyrun.shp Z:Geog476\username\Lab3\ssurgo_rockyrun.shp Set the output file to be: Z:Geog476\username\Lab3\NWI_ssurgo.shp The dialog should look like this. Click 'Ok'. Add the data to the data frame when the operation is complete. Calculate polygon area for NWI_ssurgo.shp: Review Lab 2 Part 3 for instructions about how to add a field and calculate area. Add field named 'ovl_area' type double precision 12 scale 6 Calculate the area in square meters. Calculate the percentages of the soils in each wetland in NWI_ssurgo.shp. Add field named 'pct_area' type double precision 12 scale 6 Right-click on 'pct_area' > Field calculator and enter this equation: [ovl_area]/([acres]* 4046.856) Question 2: What are the units and level of measurement of the 'acres' field? What attribute operation(s) has been performed with [ovl_area]/([acres]* 4046.856)? Do the pct_area values represent an increase or decrease in information? Summarize for the maximum single soil area of each watershed Right-click on OBJECTID > Summarize Open the pct_area and check 'Maximum' Set the output table to Z:\Geog476\username\Lab3\pct_max_area.dbf Click 'Ok' Add the data to your project when prompted after the summary is complete. Open the summary table. If you don't see it in the table of contents click the 'Source' tab at the bottom of the Table of Contents. Question 3: What is the OBJECTID of the wetland(s) with the greatest number of soil types present? What SQL attribute query will select the records of wetlands located on only one soil type? Join pct_max_area.dbf to the attribute table of NWI_ssurgo.shp using OBJECTID as the key field. Question 4:Once the tables are joined what SQL equation will select the largest soil polygon/soil type in each wetland? Which measurement framework (Table 2-6) best describes the overlay analysis to measure this soil property of wetlands? Which attribute combination method (Table 5-1) best describes the attribute phase of this overlay?
Part 4: Line overlay points Add data Y:\portage\shapefile\pc_GreenCircle.shp Y:\portage\shapefile\pc_roads.shp Open the intersect dialog: ArcToolbox window > Analysis tools > Overlay > Intersect (double-click) Use these parameters for the intersection. Open the attribute table for pc_roads.shp and perform a Summarize operation on the field 'FID_pc_Gre' to measure the number of times roads cross each SEGMENT. Question 5: What is the average number of road crossings on the Green Circle Trail's segments?
Part 5: Convert polygons to raster Add data: Z:\Geog476-Materials\SRTM\wi_srtm_500 Y:\wisconsin\dnr\orig_veg_cover\orig_veg_cover\orig_veg_cover.shp Adjust the Spatial Analyst analysis environment options: Open the options dialog: Spatial analyst toolbar button > Options In the 'General' tab set the Working Directory to Z:\Geog476\username\Lab3. Spatial Analyst will write temporary output files to the working directory. In the 'Extent' tab set the 'Analysis extent' to be the 'Same as layer wi_srtm_500'. In the 'Cell size' tab set the 'Analysis cell size' to 'Same as layer wi_srtm_500'. Click 'Ok' Open the 'Polygon to raster' tool: ArcToolbox > Conversion tools > to Raster > Polygon to raster Use these parameters to convert orig_veg_cover.shp to raster. Inspect the output grid and compare it with the input polygons. Question 6: Which measurement framework was applied to implement the conversion of polygons to raster cells? What is the output cell size?
Part 6: Combine land cover. Open the Single Output Map Algebra dialog: ArcToolbox > Spatial Analyst tools > Map Algebra > Single Output Map Algebra Read the ESRI help files on Combine and How combine works to better understand how the operation works and the nature of the output file Use these parameters: COMBINE (Z:\Geog476\username\lab3_prep\orig_veg_500, Z:\Geog476-Materials\Crop_data\NASS_WI\cdl_awifs_r_wi_2008.tif) Output file: Z:\Geog476\username\lab3_prep\combine_veg Open the attribute table for combine_veg and sort the COUNT field in descending order. Question 7: What attribute map combination method (Table 5-1) is applied with the combine operation? Question 8: What are the five biggest area changes measured with the combine operation? This question is about change, not what has remained the same. Check the cdl_awifs_r_wi_2008.tif's attribute table for the meaning of the cell values there. The metadata for orig_veg_cover has definitions of the land type categories. Question 9: What are the cell sizes for each input grid and the output grid? How might this difference affect the output from the combine operation?
Version of Feb 17, 2010