GUS 0265: Applications in GIS
Spring 2007
The purpose of this lab is to teach basic terrain and hydrological analysis GIS operations.
Objectives
The objective of this lab is to characterize the terrain, hydrology, and 1992 land cover of Chester County,
Pennsylvania.
Data
The land cover data are available in the S:/GUS_0265/NLCD_1992 folder. The land cover grid is called
‘lc_1992’ and an associated metadata file in html is called ‘lc_1992_metadata.htm’.
The elevation data are available in the S:/GUS_0265/NED folder. The grid is called ‘elevation’ and an associated metadata file in html is called ‘elev_metadata.htm’.
County boundaries for southeast Pennsylvania, including Chester County, are encoded in the ‘counties’ shapefile in the S:/GUS_0265 folder.
Note: Both rasters are in Geographic Projection and NAD83.
Warning: These rasters are big and may exceed the limits of you portable media! Why not work off
C:/temp to clip the land cover and elevation data to Chester County and transform the land cover data to
UTM, then move the data to your portable media.
Deliverables
You should turn in a 2-3 page report in the style detailed on the Lab Information web page
(http://astro.temple.edu/~jmennis/Courses/GUS_0265/lab.htm). Remember, the report must include the following sections:

Introduction: the purpose of the report.

Methods: a brief description of the data and the methods (operations) you used to do the analysis.

Results: the results of the analysis.

Conclusion: an assessment of accuracy and sources of error in the analysis.
The report should also include:
1.
A shaded relief (hillshade) map of Chester County.
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2.
A table showing the mean elevation, mean percent slope, and dominant aspect (defined here as the most frequently occurring, or majority, cardinal direction – North, South, East, West) for each type of forest cover.
3.
A map that identifies the highest point in Chester County and shows the area that can be seen from that point.
4.
A map identifying the individual watersheds (basins) in Chester County.
5.
A map of the two highest Strahler order streams in the study region (use the threshold of 500 cells to define streams from the flow accumulation grid).
Helpful Information….
First, open ArcToolbox->Spatial Analyst Tools->Hydrology and review the specific tools available to your there. Then go to the ArcGIS Help Index and type in “hydrology” and double click “Hydrology
Tools”. Browse the Help on this section to learn about what each of these hydrology tools do and how they can be applied to a hydrological analysis.
1.
Clip (Extract by Mask) both grids to Chester County then project to UTM. Resample by Nearest and use a cell size of 30 m.
2.
For the hillshade, you decide the parameters that look good.
3.
To compute the dominant aspect, compute the aspect layer, then reclassify all grid cells to either
North, South, East, or West. For example, 135-225 degrees is South.
4.
Use Zonal Statistics as Table to compute the mean slope and dominant aspect for each forest cover.
5.
To find the highest elevation in Chester County and create a point shapefile that represents that location, use a reclass function to create a new grid that has a 1 for the very highest elevation and
NoData for all other elevations. Then convert that new grid from raster to a point shapefile.
6.
To identify the area that can be seen from the highest point, use the ArcToolbox->Spatial
Analyst->Surface->Viewshed function. Use the elevation grid as the input grid, the highest point shapefile as the observer point, and leave the remaining parameters as the default.
7.
To identify the individual watersheds (for all functions, leave default parameters): a.
Derive a flow direction grid from the elevation grid. b.
Derive a sink grid from the f low direction grid. c.
If sinks exits, derive a filled elevation grid from the elevation grid (takes a few minutes). d.
Derive a ‘filled’ flow direction grid from the filled elevation grid. e.
Derive a basin grid from the filled flow direction grid. f.
Convert raster basins layer to a polygon shapefile
8.
To identify the two highest Strahler order streams: a.
Derive a flow accumulation grid from the filled flow direction grid. b.
Derive a stream grid from the flow accumulation grid by reclassifying those cells that have at least 500 other cells flowing into it a value of ‘1’ and all other cells ‘NoData’. c.
Derive the Strahler order number grid (encoding the Strahler number for each stream link) from the stream grid and filled flow direction grid. d.
Derive a stream line shapefile from the Strahler order number grid and filled flow direction grid using the ArcToolbox->Spatial Analyst->Hydrology->Stream to Feature function (check Simplify). e.
Select those stream links with the highest two Strahler orders (in the Gridcode field), export them to a new shapefile, and map them.
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