Lab 7

 

For this lab I created a fire hazard map for the area in the region of the 2009 Station Fire in Los Angeles County. This map was created using a raster digital elevation model layer, a raster layer with fuel sources based on vegetation coverage, and a vector layer with a polygon outlining the greatest extent of the Station Fire.

First, I converted the DEM into a raster layer showing the slope of elevation. I then reclassified this into five different categories from very low slope to very high slope. Then, using the reclassification parameters described in the tutorial, I reclassified the fuel source layer again into five different categories from very low flammability to very high.

I now had one slope and one vegetation layer, each with five different risk categories. Using the raster calculator, I added these two layers. Again I reclassified the result into five categories ranging from very low risk to very high risk. Finally I put the vector polygon of the greatest extent of the Station Fire over this resulting layer. The final map now shows the fire risk in the area of the Station Fire based on slope and coverage type. I have also included a map of risk based just on slope and another just on coverage type. This lab was relatively straightforward and was completed with minimal difficulties. I believe I am becoming much more proficient at using ArcGIS. 

I spoke too soon - for some reason the layers in the first map I uploaded did not upload. Here is the correct and final map now.

Lab 6

First Arithmetic Model:

[Reclass of Coverclass] + [Reclass of sl_dist] + [Reclass of Slope of elevation] + [Reclass of Soildrain] + [Reclass of Stream Buffers]

First Weighted Model:

(([Reclass of Soildrain] * .3) + ([Reclass of Slope of elevation] * .3) + ([Reclass of Stream Buffers] * .2) + ([Reclass of Coverclass] * .1) + ([Reclass of sl_dist] * .1)) * 5

Data: Vegetation type, slope of elevation, soil drainage data, and stream buffers.
Purpose: Used as a landfill development suitability analysis for the area in concern. 
Cell Size: 1000, 1000
Measurement Units: Meters
Geographic Extent: Gallatin County, Montana
Date Run: 02/13/11
Model Run For: Yongwei Sheng/Kettleman City Officials

This lab was a raster data spatial analysis exercise. I learned how to create, convert, and do spatial analysis on raster cells. Such skills have enhanced my ability to use GIS as a valuable tool for problem solving and decision-making.

I began this exercise in spatial analysis by defining the vector layer outlining the fictional county as an ‘analysis mask’. This ensured that the suitability analysis would be calculated based only on data from the county in concern.

Next I derived a layer representing the slope of elevation from a DEM of the county. Such a layer is useful for determining an area’s suitability for excavation.

Another issue to consider may be proximity to other areas of concern. In regard to landfill development, it is important to consider a new site’s proximity to nearby streams and other already existing landfills. A buffer is the tool for solving this issue. Here I created a buffer layer with four one-kilometer rings surrounding the rivers in the county.

This vector layer was then converted to a raster grid for spatial analysis. The resulting grid was a floating point grid representing the continuous elevation data. For ease of analysis, I converted this from a floating grid to an integer grid.

To determine the location of nearby existing landfills, I selected from the attribute table all of the area’s landfills that are currently open. I then made a new raster layer with grid values representing meters from any given point to the nearest open landfill.

After adding two additional raster grids describing the area’s soil and vegetation type, my data consisted of 5 layers representing 5 concerns to consider in a landfill development suitability analysis:
1) slope of elevation, 2) proximity to streams, 3) proximity to already operating landfills, 4) soil drainage, and 5) vegetation type.

The raster data in each cell of these five grids was then reclassified to create five new layers, each with cell values based on a scale of only 1-5. Each of these grid layers was assigned a particular weight based on their relative importance to this suitability analysis.

Then, using the raster calculator, the weighted values of each cell of each layer were combined. The resulting layer was reclassified to produce a final suitability layer. Each cell of this final grid considers each of the five weighted criteria and has a value of 1-5, 1 being the least suitable and 5 being the most suitable site for a landfill.

I have used these techniques to show which parts of a fictional area of Montana are the most suitable for a new landfill. But these spatial analysis techniques could also be used to solve numerous other suitability issues in land use pertaining to private and commercial real estate development, business expansion and location, resource allocation, city planning, etc.

These same techniques could be used to help solve the debate over the expansion of a landfill in California’s Central Valley. In addition to determining which areas are most suitable for expanding the landfill, these tools could also help determine whether or not the existing landfill is the cause of several contaminations and heath issues.

A buffer around vector layers locating aquifers, wells, streams, springs and other sources of water would tell if areas of the landfill were already close enough to these sources to contaminate them. A slope of elevation raster grid would help determine how contaminates are expected to spread from the landfill. And a raster grid representing the area’s soil drainage data would help determine if contaminants are draining down to groundwater below.

By using these techniques, investigators would know how close the landfill is to sources of water, how the contaminants flow from the landfill, and whether or not contaminants are draining down into groundwater. This would help enable them to determine whether or not the existing landfill is responsible for the current heath issues.

Quiz

I am AGAINST this decision that medical marijuana dispensaries may not be within 1000 ft. of places where children congregate. This ordinance is impractical on many different levels. Firstly, it is discriminates against medical marijuana dispensaries. Other substances sold within the state of California, alcohol for example, are also illegal for children to consume but are not regulated like this ordinance will regulate medical marijuana. Also, areas where children congregate is such a broad term, including public areas such as schools, parks, libraries, and even private churches, theaters, and shopping malls. If all of these areas were to be banned, there would hardly be anywhere for medical marijuana dispensaries to operate.

One can see from this map of a small area within downtown Los Angeles that of the 8 dispensaries already in operation in this location, 7 fall within these ‘areas where children congregate’. Throughout the rest of the city of Los Angeles, similar results are found. Many dispensaries would have to close, and few new ones would be able to open.

Lab 4

This assignment was straightforward and a great exercise for learning how to digitize in ArcGIS. By this point, I’ve become much better at using ArcCatalog to create geodatabases and organize my data. Creating the new shapefiles and editing their attributes was not too difficult either. I was surprised at the simplicity of the whole process of digitizing by this method. However, I did face difficulties with the borders polygons and with the features’ labels.

The Cut Polygons Features tool was indispensable, but caused issues occasionally. Sometimes an error message would come up saying it could not distinguish between the right and left side. I am not sure why this happened, or what it meant, but got around the problem each time by adding a few more vertices along the shared border. I could not figure out the point of or how to use the Auto-Complete Polygon tool, but look forward to learning this week.

I didn’t have any issues with the Modify Feature option and it worked wonders in fixing the few minor errors I made initially. It made extending and shortening lines, adding and removing vertices, and modifying polygon shapes easy tasks. Snapping was also an indispensable tool. I set the setting to snap to the edges and end points of the Iraq polygon.