1. Spatial Analysis using Vector Data # 1 Francisco Olivera, Ph.D., P.E. Srikanth Koka Department of Civil Engineering Texas A&M University

2. Map Analysis Map analysis consists of inferring information – necessary for a given engineering/scientific task – from general information contained in digital spatial datasets. In this case, the map analysis will use vector data (i.e., features such as points, lines and polygons).

3. Sample Dataset Five feature classes are used to explain the analysis tools: A: polygon dataset B: polygon dataset C: line dataset D: point dataset E: point dataset

4. Sample Dataset In addition to geometric information (area, perimeter and length), the feature classes have the following fields: AConc: Mass of a certain fertilizer per unit area (kg/m 2 )(I) ATrees: Number of trees(E) BOwner: Land owner(I) CName: Road name (I) DRain: Annual precipitation depth (mm)(I) ERain: Annual precipitation depth (mm)(I)

5. Dissolve Creates a new feature class in which all features that have the same value for a given attribute are aggregated into a single record Applies to one dataset only User has the option of defining how attributes are recalculated

6. Dissolve Dissolving B so that all land that belongs to the same person is represented by a single polygon. Select the dataset you want to dissolve, select the key attribute which will be used to aggregate the features, and enter the path and name of the new feature class. Select how the attributes shall be calculated (more than one option is allowed). The key attribute is copied by default.

7. Dissolve After dissolving the feature class, boundaries between adjacent polygons that are aggregated disappear. If aggregated polygons are not next to each other the effect of dissolving will not be obvious in the map, but will be in the table. The figure shows only one record selected. The two polygons were two different records before dissolving.

8. Dissolve After dissolving the dataset, the key attribute (i.e., BOwner) is copied, and two new attributes are created: Count_BOWNER: number of polygons aggregated Sum_Area: sum of the previous attribute Area (as requested in previous window)

9. Append Appends features from input shapefiles/feature classes to a target shapefile/feature class. Attributes of the input are transferred to the target if the fields have the same definition.

10. Append The TEST option under Schema Type forces the input schema to be the same as the target schema; otherwise, the input is not appended. The NO_TEST option under Schema Type does not force the input schema to be the same as the target schema; however, only those fields with the same definition are transferred.

11. Append Appending D and E so that all precipitation stations are in a single feature class After appending the input, all points are features of a single feature class.

12. Append After appending the feature classes with the NO_TEST option, the resulting feature class attribute table has the attributes RecNo and DRain because those are the attributes of D (the target feature class). Attribute ERain of E is not transferred, while RecNo is transferred. If Recno refers to the record number, it would be advisable to update it.

13. Clip Creates a new feature class by clipping an input feature class with another clipping polygon feature class. The attributes of the input feature class are not altered (including the geometry). Applies to two feature classes

14. Clip Select the feature class you want to clip, select the polygon feature class you want to use to clip and enter the path and name of the new feature class.

15. Clip Clip out C with the selected polygons of BDisslv to identify the road segments that are in Kelly's, Mary's, and Melissa's property. After clipping out the C feature class, only those segments within the selected polygons of BDisslv are considered. Note that features in the resulting feature class are obtained by intersection of the input and the outline of the clipping feature class.

16. Clip After clipping, the attributes of the input feature class are copied but not updated. The length, area and perimeter need to be recalculated.

17. Intersect Creates a new feature class in which the features are the result of intersecting the features of input feature classes. Resulting features have attributes from all input feature classes. Applies to two or more datasets.

18. Intersect Select the input feature classes you want to intersect and enter the path and name of the new feature class. Select the type of output features you want under Output Type.

19. Intersect Intersecting A and B so that for each resulting polygon the mass of fertilizer per unit area and the owner are a unique combination of values. After intersecting the feature classes, the number of polygons significantly increases.

20. Intersect After intersecting, all attributes from both datasets are copied. The attributes Length, Area and Perimeter correspond to the original feature classes and have to be recalculated.

21. Union Creates a new feature class by combining the polygons of input feature classes. The resulting dataset has the extent of all input feature classes. Applies to two or more polygon feature classes. Union is very similar to Intersect, but in Union the parts of the polygons that do not intersect have zero for the non-defined attributes.

22. Union Select the input feature classes, and enter the path and name of the output feature class.

23. Union Union A and B so that for each resulting polygon the mass of fertilizer per unit area and the owner are a unique combination of values. After "unioning," the feature classes, the number of polygons significantly increases and the resulting dataset includes attribute data from both sources.

24. Union After "unioning," all attributes from both datasets are copied. Polygons that correspond to only one dataset get zero or blank for the attributes of the other dataset. The attributes Length, Area and Perimeter correspond to the original datasets, and have to be recalculated.