Week 10 - Spatial Analysis of Vector & Raster Data / Vector Analysis 2
In this week's lecture we furthermore learned about the astounding capabilities of ArcGIS geoprocessing tools and spatial analysis when working with vector and raster data formats. The goal of spatial analysis in GIS is to extract new data, derive new knowledge from it, and thus use it to provide better solutions and make wiser decisions for big problems.
For vector analysis, we covered topics on buffering on lines, points, and polygons, as well as the super awesome Overlay Tools: Point-in-Polygon, Line-in-Polygon, Intersection, Union, Symmetrical Difference, Identity, Clipping, Erasing, and Splitting (see diagram reference to the left).
For our lab assignment we gained experience using both buffer and overlay vector analysis toolsets to create a map depicting potential camp site locations in De Soto National Forest in Mississippi, as shown above. The final objective of our map deliverable was to showcase potential camp site locations that met these qualifications: within 300 meters of a road, within 150 meters of a lake, within 500 meters of a river, and outside of conservation areas.
To achieve these spatial qualifications, I first created a 'fixed distance buffer' layer from the 'Roads' feature class, then I created a 'variable distance buffer' layer from the 'Water' feature class. The 2 newly created buffer layers were then 'unionized' into one feature class using the Union Overlay Tool; and then I did a Selection where attributes were queried if both columns 'insd_rbuf' and 'insd_wbuf" (the 'inside buffer fields') equaled 1. I exported the selected data to its own feature class. At this point, I had met 3 of the required qualifications. The last step was to exclude conservation areas from the unionized campsite results. (Why is this important in real life? Campers are not allowed to disturb plants or animals located in conservation areas.) So, I ended up using the Erase Tool so that only those portions of the input features falling outside the boundaries of the erase features remained, to create the new feature class, 'Potential Camp Sites', as depicted in the legend in my map. Lastly, I exploded the features of Potential Camp Sites using the Multipart to Singlepart tool found under Data Management > Features.
In our lab assignments, we work with relatively small data, but in the real world, GIS users are required to run multiple tools on various layers (like how we just did), and within those layers there are literally sometimes thousands of features. That's why our Professor provided us with an introduction to ArcPy during this week's assignment. So what are the advantages of using ArcPy? Simply put, it allows users to run multiple processes and functions at once -- with a click of a button! Once a python script has been written, it can be copied and pasted over and over again, only to make small adjustments for big time-savings and big results. For our lab assignment, we experimented using ArcPy by running buffers on the aforementioned layers at 200, 250, and 300 meters.
For our lab assignment we gained experience using both buffer and overlay vector analysis toolsets to create a map depicting potential camp site locations in De Soto National Forest in Mississippi, as shown above. The final objective of our map deliverable was to showcase potential camp site locations that met these qualifications: within 300 meters of a road, within 150 meters of a lake, within 500 meters of a river, and outside of conservation areas.
To achieve these spatial qualifications, I first created a 'fixed distance buffer' layer from the 'Roads' feature class, then I created a 'variable distance buffer' layer from the 'Water' feature class. The 2 newly created buffer layers were then 'unionized' into one feature class using the Union Overlay Tool; and then I did a Selection where attributes were queried if both columns 'insd_rbuf' and 'insd_wbuf" (the 'inside buffer fields') equaled 1. I exported the selected data to its own feature class. At this point, I had met 3 of the required qualifications. The last step was to exclude conservation areas from the unionized campsite results. (Why is this important in real life? Campers are not allowed to disturb plants or animals located in conservation areas.) So, I ended up using the Erase Tool so that only those portions of the input features falling outside the boundaries of the erase features remained, to create the new feature class, 'Potential Camp Sites', as depicted in the legend in my map. Lastly, I exploded the features of Potential Camp Sites using the Multipart to Singlepart tool found under Data Management > Features.
In our lab assignments, we work with relatively small data, but in the real world, GIS users are required to run multiple tools on various layers (like how we just did), and within those layers there are literally sometimes thousands of features. That's why our Professor provided us with an introduction to ArcPy during this week's assignment. So what are the advantages of using ArcPy? Simply put, it allows users to run multiple processes and functions at once -- with a click of a button! Once a python script has been written, it can be copied and pasted over and over again, only to make small adjustments for big time-savings and big results. For our lab assignment, we experimented using ArcPy by running buffers on the aforementioned layers at 200, 250, and 300 meters.
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