Working with ArcPro this week
This weeks lab is going to make use of ArcPro. ArcPro and QGIS are very similar in how they work and the layout of the software. As we are using a new piece of software this week, we will make use of this week’s lab time and next week’s tutorial time to complete the materials and questions.
Getting started with ArcPro
Starting the software is the same as others, under the ArcGIS menu launch ArcGIS Pro. Setup a workspace for this week’s lab:
- Click Map under the New column
- Create a new project and folder in your K:/geog204 folder called lab4 (very inventive)
- The project name is not important – as we will save our work as shapefiles again this week (see below)
Setting up folders for use in your project
Once ArcPro is open you should have a menus on to, a map in the middle, table of contents (layers panel) on the left and catalogue (browser) on the right.
Setup folder connections in the Catalogue panel by:
- Right click on Folders
- Add New folder connection
- Navigate to your k:\geog204 folder
- Repeat to add the L:\GEOG204 folder
Simple Query based on Attributes
In this lab, you will be exploring more functionality available in ArcGIS and learn basic analysis skills.
Add the following datasets from L:\GEOG204\lab4 folder
fcover, trails, lakes, wetlands
Finding the area with ‘spruce ‘as the leading species
- As with QGIS, right click on the fcover layer and open the attribute table
- Choose select by attribute in the top menu of the table panel
- Setup a new selection
- Select for SPEC_CD_1 equal to “S”
This follows the naming conventions for forest species:
Using the an operator as defined below:
Finding the areas that have Spruce as the leading species, stand age greater than 30 years and the leading species cover 70% of the area
Use the query builder or type in the following expression in the query box
(“SPEC_CD_1” = ‘S’) AND (“SPEC_PCT_1” > 70) AND (“STAND_AGE” > 30)
You will save your new selection to a shape file on your K: drive by repeating the selection in the export by:
- Right clicking on the fcover layer
- Data –> Export Feature
- Setup the export pane as below
- ENSURE you add the .shp to the name of output (this will provide a shapefile as a result)
Finding the distance from points to the nearest line features
In some cases, we want to know the spatial relationship between features. For example, with our sampling plots data, we want to know if a water source has a big impact on the growth of trees. In other words, we want to
know if the trees that are close to a water source, grow better than those that are further away.
Add the creeks and sample data to your project from the lab4 folder in the L:\GEOG204 folder (you may have to refresh the folder in catalogue).
Perform the selection by:
- Access the Analysis tab on the top or ArcPro
- Use the sample layer as the target
- creeks as the join
- Match option is Closets
- Set a field name for the distance (i.e. “distance”)
- Click the spatial join button and set the join up using the image below as a model
The resultant attribute table will have all the attributes of the nearest creek as well as the distance as the first of the new fields.
Try another query using the table selection to see how may sample points are within 5 metres of a creek.
Line-on-polygon and polygon-on-line selection
Sometimes we need to know which line feature overlays the polygons with specific attributes. For example, which creeks (water sources) pass through young to middle aged forest stands (polygons). Use the layer you created for spruce older than 70 years old and select the creeks that pass through these polgons.
Using the Toolbox
The Toolbox in ArcPro is much the same as the processing toolbox in QGIS. Hit red “Tools” button in the top menu of ArcPro and it will launch a geoprocessing window
Search: “select by location” in the search field of the toolbox panel and choose this tool from the list of options (it should be the first tool).
Fill in the panel to find the polygons that have creeks running through forest layer:
Test your skills by combining a selection
Now you know how to find creeks that intersect with your forest cover dataset, try a new selection with the following criteria:
- Load the bird_nest layer from the L:GEOG204\lab4 folder
- Use the orginal fcover layers (not your species and age forest cover layer)
- Find which forest cover polygons intersect with the bird_nests layer
- From this bird presence fcover selection, select which polygons have lakes in them
We are looking for fcover polygons that intersect with both bird_nests and lakes
Spatial overlay is a process whereby themes or datasets sharing the same spatial extent are compared with resultant layers produced. We are essentially comparing the simple feature locations of different layers.
In GIS, where lines intersect between one theme and another, vertices are created. Where lines or points share the same space as polygons, the lines and points inherit the attributes of the spatially corresponding polygons. New layers areformed which can take on the attributes or coordinate properties of input data sets. Some or all features from the input data sets are passed on to the output. Attribute values from both input data sets are passed on to the output data set. Overlay analysis is multi-layers analysis and the operations modify geometry and generate a new dataset
Differences between Select by Attribute/Location and overlay analysis are:
– Selection operations extract a subset of spatial features from one dataset using other layers as references. No modification on geometry to resulting dataset. So selection analysis is usually called single layer analysis
– Overlay operations perform multi-layers analysis and take the part of input features from multiple layers to the output dataset based on spatial relationship. Changes on geometry of the output dataset will be made
after the operation.
All the datasets required for this part lab are located at L:\GEOG204\lab4
bird_nests – Bird nest locations around Forests For the World
creeks – Creeeks
slopes – Slopes and aspect information of the terrain
fcover – Forest coverage data
trails – Trails system
lakes – Lakes
wetlands – Wetlands
bndy – UNBC map boundary
Start a new project
We will be starting a new project in ArcPro and saving our first map file. To start this use these steps:
- Click the “Project” tab on the top menu
- Click “Map” under the template column (as we did before)
- Create a new project in your lab4 folder called analysis
- You can save change to your project from above if you wish
- Right click on the map in the table of contents
- Save as map file
- Save to your lab4 folder and call the map file – analysis
- Add all the layers mentioned above
- Turn off the visibility of the slopes layer
- Resave your map – you can just hit the save button on the very top of ArcPro (ctrl-s)
The BUFFER tool creates a new output by generating buffer zones around input features. Input features can be polygons, lines, or points. Output features will always be polygons.
Assume that young birds often search for food within 50 meters of their nest while the older birds search for food within 100 or 150 meters of their nest. We can use the buffer function to determine the area where birds
are showing up frequently. We will create two buffer datasets on bird_nests.
Buffer bird_nests at 50 metres
- Activate the Analysis tab on the main menu
- Search out buffer in the geoprocessing tools
- Set up your analysis accordingly
You should now see some nice round polygons around your birds nests. You can zoom in by switching back to the Map tab and use the navigation tools
Buffering with multiple buffers – 50, 100, 150
- Find the Multi Ring Buffer tool
- Add in the values accordingly …
Examine the attribute table of each buffer dataset (ie. birds_buffer-50 and birds_buffer-30-100-150). The data field Distance is generated automatically for the multiple ring buffer dataset.
You can also style your new layers in a similar fashion as to QGIS. Right click –> symbology –> set up your colours
We are going to perform an operation to extract where the geometries of two layers intersect with each other. Check out ESRI’s description of intersect
Now we want to know the area that falls into the 50 meters buffer of bird
nest and with ‘Trembling Aspen’ (AT) as the primary spices. To solve this
problem we need to use INTERSECT.
The INTERSECT tool overlays two datasets to create a single output. Only those features that occupy the same spatial location in both datasets will be preserved in the output dataset. The features in the output dataset will
have all the attribute data from both input datasets.
Select by attribute
For the question mentioned above. You need to first perform a Selection by Attributes on fcover to get the areathat have ‘Trembling Aspen’ (AT) as the leading species. You did this for “spruce” before, just substitute for ‘AT’ the expression such as:
“SPEC_CD_1” = ‘AT’
- Select for trembling aspen in the fcover layers
- Find the intersect tool in the geoprocessing tools
- add both the layers in as inputs
If all went well, you should have the intersections of the selected fcover layer swith the buffered birds.
The intersection will provide attributes from both layers. This includes the old area and perimeter values. These values are no longer accurate and need to be updated. As with QGIS, this is easily accomplished:
- Open the attribute table of the layer
- Right click the AREA field –> Calculate Geometry
- Pick target fields of ‘AREA’ and ‘PERIMETER’
- Pick property of ‘area’ and ‘perimeter’
Clipping is an often used spatial overlay. It is similar to interesecting, but it is used to extract the features and attributes of one layer but using a second layer as a “cutter”. The result is a subset of the ‘input’ layer, wherby intersecting combines two layers in shared geometries. Check out the gis wiki explanation of clipping
In some cases, a dataset covers much larger area than we are interested in. In this case we can use CLIP tool to clip trails with the bndy polygon layer. The bndy polygon is the “cookie cutter” in this case.
Clipping trails with the study area
Clipping follows the same procedures as the above overlays:
- Find the clip tool in geoprocessing
- Tee input layer is trails
- The clip features is the bndy layer
Assignment 5 marks – Due the week of October 26.
You will be given an extra week to finish this assignment as we are working with new software. It will most likely not take the extra time provided, but
In this assignment, you are required to perform GIS analysis for the Forest For the World area:
- Identify the level of difficulty of trails based on slope degree
- Locate the potential campsites along the trails and lakes and must be in a relative flat area
The data needed for the assignment is:
ffw_bndy is the park boundary for the Forest For the World. As we are only interested in the Forest For the World area,
- clip lakes, trails, slopes with ffw_bndy as the cookie cutter and save them as lakes_ffw, trails_ffw, slopes_ffw respectively.
- Recalculate LENGTH and AREA for each features if necessary. Use the clipped features for analysis
1. Identify the level of difficulty of trails based on slope degree (1.5 marks)
- The level of difficulty of trails based on slope can be identified by intersecting the trails with slopes.
- Recalculate LENGTH
- Symbolize the resulting layer based slope (Degree_SLO) in graduated colour with 3 classes: 5, 15 and greater than 15
- Note down the total length for each trail class: slope <=5 (easy access), 5 15 (difficult) respectively.
2. Locate the potential campsites along the trails and lakes (1 mark)
The potential campsites need to meet the following criteria:
- Must be within 20 meters distance of trails and Shane Lake (the biggest lake)
- Should be in relatively flat area (slope <=5)
- Locate the 20 metres area along the trails with BUFFER tool. Make sure to dissolve the barrier
- Create a 20 meters buffer around Shane lake (Note: set Side Type to OUTSIDE_ONLY, this will exclude the waterbody area). Check the buffer options to: Make sure to dissolve the barrier
- Filter out the area with slope <= 5 degree (slopes)
- Intersect the results from step 1, 2, 3. Recalculate AREA. Note down the total area for the potential sites.
3. Produce a map showing trail classes, potential campsite with proper map tile, legend, scale and name (2.5 marks)
Save your answers together the map as lastname_firstname_geog204_A4 in WORD file and send it to your TA