Advanced Geoprocessing

Key Terms and Understandings

• Buffering:

Buffering in ArcPro and ArcPro allow you to create a set distance (or space) around whatever point, line or polygon you are trying to work with. This could be to mark ecological areas around rivers or streams, how many coffee shops are within a mile from your new job, so many things. You can also use buffers that overlap from two different areas of interest to find where something is in common for those.

• Select by Attribute:

Select by Attribute allows you to pick specific parts (features) of a shapefile, this could be polygons(like areas around a county), points (like trees in a forest), lines (like roads), etc. based on something they have in common. The attribute table tells you what fields a shapefile has that tell you something about it, like it's location or name. The attribute table could have a few fields or a ton depending on what information was put in from the data collected for that shapefile. You set a query which looks something like "I want all the objects from [your_shapefile] where the attribute in 'COUNTYNAME' (field) is equal to 'CACHE'(attribute you are interested in within field".

• Select by Location:

Select by location works similarly to 'Select by Attribute' except that instead of an attribute being your limiting factor, it is where those features are in relationship to another shapefile. So you tell ArcPro what shapefile you want to select the features from, what relationship you want them to have with your limiting shapefile. The relationship could be things like, 'completely within', 'intersecting', 'contains', etc. The query looks something like "I want to select all the features within [shapefile] that are [relationship] [limiting shape file]". So, I could say something like "I want to select all the features with 'Cities' (shapefile) that are 'completely within' (relationship) 'Cache' (other shapefile or feature selection from shapefile). This would give me all the cities within Cache County.

• Map Series:

A map series is a collection of map pages, sometimes called map sheets, that are map from a single layout that represents a geographic area. A spatial map series is where each map page displays a portion of the larger geographic area based on something like a road or point or area of interest. It basically takes a larger map and splits it up into more detailed bite-sized pieces to better understand what the map is saying as well as make it more useful.

Description:

In this lab, I was tasked with creating 50 random sites to collect vegetation data for the BLM within an area of interest. After loading up a base map within the proper coordinate system (NAD 1983 UTM Zone 12N), I created 1000 random points within the area of interest. This was to ensure that the points were not decided with a personal bias, therefore improving the accuracy of the data and resulting research conclusions.

I used the the "Create Random Points" tool in ArcPro, using my Area of Interest file (AOI) as the constraining feature class. This is to set the boundary in which these points would be generated. I set the minimum allowed distance to 50 meters so the points were generated were at least that far apart from one another. A new feature class was created by doing this that I named "initial points". I used the "Buffer" tool, choosing my "initial points" feature class and setting the distance to 10 meters. The buffer tool takes whatever value you put into distance and uses that as your radius around your shapefile, in this case points.

I needed by points to be completely within BLM land and within 500 meters of non-busy roads (those with a speed limit of under 35). First, I needed to make a layer of just BLM land. Using the 'Select by Attribute' I selected all the land ran by the BLM from my total state landowner file. When using 'Select by Attribute' you enter a query expression, basically asking a question and then selecting by the result of that question. There a lot of options you can use to ask about any field in the attribute table (in this case 'AGENCY') using statements like 'equal to', 'less than', etc. The query expression I entered was AGENCY (the attribute I was interested in) is 'equal to' 'BLM' (the specific agency I wanted). So, any row (area on map) in that column where it had the value 'BLM' was selected. I right-clicked the layer in the menu and selected 'Make Layer from Selected Features'. This makes a new feature layer with only the data that was selected.

By using the 'Select by Location' tool, I can select features from one feature class based on its location within another. For my parameters, I used the layer with my buffer points as my inputs (because that's what I wanted to be selected), the relationship to ' is completely within' and my selecting features to my BLM layer that I created in the last step. You could think of it as writing, "I only want the points within my buffer layer that are completely contained within my BLM layer. Kind of like the tool I used to create random points within the area of interest, this selects only the points within a boundary I specify. Once I had those points selected I created another new shapefile by right-clicking and selecting 'Make Layer from Selected Features'.

After uploading a shapefile for all the roads, I used 'Select by Attribute' to select all the roads with speed limits under 35 mph. Then I used 'Select by Location' to create a shapefile for the points within 500 meters of roads. I set my input to the sites within BLM land (the shapefile created in the previous step), my relationship to 'within a distance', used my roads shapefile as the selecting feature (or boundary) and the search distance to 500 meters. This creates a shapefile of all the points that are within BLM land within 500 meters and not near roads quicker than 35 mph. The selection for location only acted upon the files I already had selected from roads file.

At this point I'm still sitting at almost 400 points and the BLM only needs 50 sites to use, so I needed to narrow that down. Using the "Subset Features" tool I input the shapefile from above, (buffers, within 500 meters of a road less than 35 mph, and within BLM designation) and set my subset to a defined value of 50.

Now I have a map that has 50 points all within the parameters that the BLM needed. In order for this information to be used by those doing the data collection I decided to make a map book. This way there would a single point on each page, a zoomed in view of the point and a reference map zoomed out a bit from the map to see surrounding topography and landmarks, such as roads. I created a new layout for the map and inserted a data frame with an aerial basemap. In the layout tab, I went to the page setup group and chose 'Map Series", choosing to create a spatial series. I set the map extent to center on the point(s) at a reasonable scale. This created a page for each of my data points with the point nicely centered on the page. I then created another data frame to serve as the reference map in finding the point and set the scale to be more zoomed out than the other. I constrained it the other map frame's center so that the point was still centered, just seen from further away. I added a title, short description, data credits, scales, and a legend to make the map easier to read and understand.

To download a PDF of all 50 sites click here.