Lab #10

Geoprocessing- Geoprocessing takes an input dataset, performs an operation on that dataset and returns the result of the operation as an output dataset. Common actions are to include a geographic feature overlay, feature selection and analysis, topology processing, raster processing, or data conversion.

Model- One process or a sequence of connected processes in ModelBuilder.

Multipart polygon- A digital representation of a place or thing that has more than one part but is defined as one feature because it references one set of attributes. This can be a point, line, or polygon.

Discrete Data- Data that represents phenomena with distinct boundaries. Example include property lines and land-use areas.

Continuous Data- Data that varies without discrete steps such as temperature and elevation data.

Esri Grids- This is a way that Esri stores raster data that defines geographic space as an array of equally sized square cells arranged in rows and columns. When the grid is on the map, cells are assigned colors according to their numeric values and each grid is references by its x,y coordinate location.

No Data- The absence of recorded data in raster data. This does not equate to a value being 0. The measurement just has not been taken for this cell.

Neighborhood- User-defined are used to establish new output values. Neighborhood functions establish new values for locations use the values of other locations within the given area.

Intermediate Data- Any data in a process that did not exist before the process existed and that will not be maintained after the process is executed.

Reclassification- Process of taking input cell values and replacing them with a new output cell values. This is used to simplify or change the interpretation of raster by changing a single value to a new value or grouping ranges of values into single values.

1.      Explain how dissolve works.

a.       Dissolve merges polygons together to create a larger polygon that incorporates all of the areas data through specific common characteristics. For example, if there are over lapping layers, they would be merged into one single polygon rather than have polygons overlapping one another.

2.      Give one example of when to use dissolve and when to use clip

a.       You would use dissolve rather than clip when trying to merge data together. With dissolving you are incorporating the data that is related together. When clipping, it is like cutting out the data that you are not trying to focus on.

3.      Give two different applications for the buffer tool

a.       One application of buffers is for magnitude of earthquakes. The circles around origin of an earthquake radiating out are buffers because they are a constant distance around the feature. Another application of buffers could be for strength around a cell tower. There would be a constant distance around the cell tower.

4.      What is the difference between union, intersect, and merge?

a.       Union is when the polygons are joined together and new polygons are made where the first polygon does not overlap anything, the second polygon does not overlap anything, and the area of overlap between the two polygons. An intersect only shows the area of polygons where they intersect or overlap. A merge just combines the two polygons to create a new shape.

5.      Give an example of when you would use union over merge

a.       An example of when I would use union over merge would be if I am comparing two different events that happened in the same area. For example, if there was a fire that occurred on a hillslope and I was showing the extent of that with the incident of a slope failure. It would be helpful to see a union of the two separate events in order to see the extent of each rather than merging them together.

6.      Is the clip tool used for only vector, only raster, or both?

a.       The clipping tool can only be used for vector data. Arc GIS specifies that the data can be points, lines, or polygons which are vector data only.

7.      What might you use a mask for?

a.       I might use a mask when I have a lot of data but I only need a certain amount. The mask will take that portion of data that is needed and match the extent to other data that I am used for a specified area.

8.      How are environment settings use in arc map?

a.       The environment setting is used to match the ArcMap session and all the tools that I am currently using in the model.

9.      What might be an advantage of using model builder?

a.       An advantage to using model builder could be that it allows you to organize the inputs, tools, and outputs that will be used to perform the analysis.