Lesson Report 7: Introduction to Raster GIS Analysis

by Diana Jo Lau

Introduction

Ellieus Environmental analyzed the hydrology, elevation, land use, climate and soils of a small portion of

Napa Valley, CA to identify potential vineyard zones. This project will benefit grape farmers and

winemakers .

Lesson Objectives

- To convert vector data into raster data.

- To convert elevation data to hillshade and aspect layers.

- To use interpolation tool to interpolate a continous surface from sample points.

- To use the raster calculator tool to perform calculations in between raster layers.

- To create buffer zones from raster layers

- To perform distance calculations of rasters using Euclidean distance.

- To use the reclassify tool to create discrete data from continous surface grids.

- To know the definition of discrete and continous data.

Project Criteria

The potential vineyard site should follow the following criteria:

1. Land use must be agriculture or undeveloped.

2. The site must be outside of floodplain and more than 100 meters from a stream.

3. Slope orientation must be between 112-337 degrees or flat land.

4. Average minimum temperature more than 35 degrees.

5. Average maximum wind speed less than 25 mph.

6. Soil depth between 31 - 72 inches.

7. Soil drainage between 1.5 - 3 (medium to high).

Results and Discussion

The GIS data was downloaded from the link provided in Lesson 7. The data was already projected to

UTM-1927 projection Zone 10 (King, Walrath, & Zeiders, 1999-2013a). Additional data (ownership layer)

was downloaded from the Try This! section in Lesson 7. Once all layers were added in the data frame the

cell size was set to 10, the folder and work extent were specified in the Geoprocessing Environment

Setting. A cell size of 10 is equivalent of a square that is 10 meters each side with an area of 100 square

meters.

The land use polygon layer originally downloaded, included 80 records of land use types repeated. Using

the Dissolve Tool same land use types were combined resulting in four (4) records as shown in Figure 1.

The four records were reclassified to obtain only the land use as specified in the project criteria.

The elevation raster downloaded was converted to hillshade and aspect using Surface in the Spatial

Analyst Tools, refer to Figure 2. The aspect describes the slope orientation, the values created represent

the north (0 degrees), east (90 degrees), south (180 degrees) and west (270 degrees) direction of the

aspect, and flat areas are represented as -1 (King, Walrath, & Zeiders, 1999-2013b).

A buffer zone was created from the hydrology raster as shown in Figure 3. Floodplain map and

hydrology buffer were combined to identify the areas greater than 100 meters outside the flood plain.

Interpolation of soil depth, soil drainage, maximum wind speed and minimum temperature was

performed using the Spatial Analyst Tool, Interpolation. Figure 4 shows an example of the interpolation

results and reclassification of soil depth rasters.

Figure 5 depicts the potential vineyard zones after analyzing the hydrology, soils, floodplain, climate and

land use layers. A total area of 1,295 acres of suitable land was estimated. In Figure 6, a table of total

cells (counts) of suitable and unsuitable land is specified and a field called "acres" was created. The new

field depicts the total area in acres of unsuitable (value 0) and suitable (value 1) land; to obtain the area,

the count value was multiplied by 100 sq. m., the result was converted to sq. ft., then from sq. ft. to

acres. the following formula was input in field calculator (( [COUNT] *100) *10.6739)/43560.

The Try This! results are shown from Figures 7 through 9. A layer depicting public and private land was

added to the existing results. This polygon layer was converted to raster and reclassified using the value

public and private. The result shown in Figure 7 depicts the public and private land that is suitable for

vineyards. Since the project criteria specifies that only private land must be used, Figure 8 shows the

private land suitable for vineyards. An area of 739 acres of private land was found suitable for vineyards.

The suitable area eliminated was 556 acres of public land. The latter value was computed by subtracting

the suitable area in Figure 6 from the suitable area in Figure 9 (1,295 - 739 = 556).

Figure 1 Land Use Maps. Image "1. landuse_dslv" was created after using the Dissolve Tool to Dissolve Land Use polygon then create a raster. The raster was reclassified in two (2) categories, suitable land (1) and unsuitable land (0) as shown in "3. rc_lu_raster" layer in the table of contents.

Figure 2 Elevation Maps. The elevation raster provided was converted to hillshade to give a 3D effect of the terrain. The orientation of the terrain slopes is depicted in the aspect layer. The aspect layer was reclassified in two (2) categories, suitable land (1) and unsuitable land (0) as shown in "3. Aspect Reclassified" layer and "rc_aspect" in the table of contents.

Figure 3 Hydrology Maps. The hydrology layer was converted to raster. The hydrology raster was used to calculate the distance of each point to the hydrology line using the Euclidean Distance tool, the result was reclassified giving a buffer of 100 meters away of the water body. The hydrology buffer and flood zones were combined to create a map showing two (2) categories, suitable land (1) and unsuitable land (0) as shown in "2. Hydrology Buffer and Flood Zones" layer and " HydroBuffer_flood " in the table of contents.

Figure 4 Soil Depth Maps. The soils depth was interpolated using IDW to find the soil depth in all the map. The soil depth raster was created as a result of the interpolation, then the raster was reclassified in two (2) categories, suitable land (1) and unsuitable land (0) as shown in "2. Soil Depth Reclassified" layer and "rc_soildepth" in the table of contents.

Figure 5 Potential Vineyard Sites in Napa Valley, CA. The areas in yellow meet all the criteria of the project.

Figure 6 Snapshot of the table showing the total area of suitable and unsuitable sites. The total area of suitable sites is 1,295 acres.

Figure 7 Public and Private lands of suitable vineyard sites and floodzone areas.

Figure 8 Potential Vineyard Sites in Napa Valley, CA after removing public lands. The suitable sites are depicted in green.

Figure 9 Snapshot of the table showing the total area of suitable sites after removing public lands. The total area of suitable sites is 739 acres.

Conclusion

Ellieus Environmental concluded that 739 acres of land are suitable for vineyards a small portion of Napa

Valley, CA. A cell size 10m x 10m was used to create these maps, which was appropriate for this project.

Greater cell size will produce lower resolution and a generalized analysis; unlike lower cell size will allow

analysis of small areas such as small parcels. As studied in GEOG 482, satellites provide higher resolution

data, for example, the highest resolution of global topography and bathymetry data can be obtained

from ETOPO1 (1 arc-minute) (DiBiase and others, 2012). This project would be better analyzed with

higher resolution of topography data, this can help determine if isolated spots of suitable areas are

really suitable for vineyards.

References

DiBiase, D. and others. (2012). Nature of Geographic Information. The Pennsylvania State University.

Retrieved April 3, 2013 from http://natureofgeoinfo.org.

King, E., Walrath, D & Zeiders, M (1999-2013a). Problem-Solving with GIS, Lesson 7, /Part 1, Section b. The Pennsylvania State University World Campus Certificate/MGIS Programs in GIS. Retrieved April 10, 2013. King, E., Walrath, D & Zeiders, M (1999-2013b). Problem-Solving with GIS, Lesson 7/Part 2, Section a. The Pennsylvania State University World Campus Certificate/MGIS Programs in GIS. Retrieved April 10, 2013.

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offering of The Pennsylvania State University. The student, named above, retains all rights to the

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