Exercise 1: Create Tree Map Manually

Download Data

Start out by downloading the WIGLOSR database. Unzip it and you will find a geopackage and the database documentation. For this walk through I will use QGIS version 3.28.15, but you can just as easily use ArcPro.

Add Data

Let’s start out by opening QGIS and adding data from our geopackage (gpkg) to our map.

In the Browser pane, right click GeoPackage and select New Connection. Select the geopackage you downloaded and click Open.

We’ll add the townships, corner_obs, and witness_trees datasets.

Zoom to Township

Choose the township you would like to make a witness tree map for; in my case I will select T23N R08E.

We can filter our layer to only show the township we are interested in by right-clicking on the layer in the Layers pane and selecting Filter. In the section labeled Provider specific filter expression enter dtr=42308.

Click okay, then right-click on your layer and select Zoom to Layer.

Township Buffer

In order to select the needed witness tree points, we need a slightly fuzzy search since many points lie right near the border of the township. We’ll add a 100m buffer to assist in this.

We’ll use a virtual layer to store this buffered township as it is ephemeral. Go to Layer > Add Layer > Add/Edit Virtual Layer.

We can change the Layer name to something like 42308_100m_buffer, then click the Import button and select townships. For the Query we’ll enter the query below. Note that we do not specify the township number because we already filtered the townships layer.

SELECT ST_Buffer(geometry, 100)
FROM townships

Click Add then Close.

Extract by Location

Open up the toolbox by selecting Processing in the top menu then Toolbox. In the Processing Toolbox search Extract by location and select the tool.

We will extract features from witness_trees, where the features intersect, by comparing to features from 42308_100m_buffer. Keep the Extracted (location) blank. Click Run then Close.

Rename the new layer, Extracted (location), to something like witness_trees_42308.

Witness Trees

Before we view the witness trees as polygons we’ll need to add some additional fields, and for that we’ll need to add another layer to the map that we can use in a join. Find the observations table in the geopackage and add it to the map as a layer.

Vector Join

First let’s join the observations table on dtrsco, adding only the ptype field with no Custom field name prefix. Right-click on the witness_trees_42308 layer and select Properties, then select Joins from the left menu. Click the plus button near the bottom to add a join. Fill it out as mentioned before and as seen below and click OK.

Add Fields

Second, we’ll add some additional fields that we’ll use later as variables in the symbology.

Select Fields from the left menu and click Field Calculator button at the top that looks like an abacus.

sp_class

Check the Create virtual field box
Use the following inputs:

Output field name
sp_class

Output field type
Text (string)

Expression:

CASE 
  WHEN sp IN ('OA','LO','RO','WO','BO','SO') THEN 'Oak'
  WHEN sp IN ('PI','RP','HP','WP','JP') THEN 'Pine'
  WHEN sp IN ('FI','SP','HE','WC','CE','TA') THEN 'Other Coniferous'
  WHEN sp IN ('BA','RE','SU','WB','BI','LI','WA','MA','AS','EL','BU','IR','AH','YB','AL','WM','HA','HI','BB') THEN 'Hardwood'
END

Click OK

Use the field calculator to add a couple of more fields in a similar fashion:

diam_class

Check the Create virtual field box
Use the following inputs:

Output field name
diam_class

Output field type
Decimal (double)

Expression:

CASE 
  WHEN diam<=5              THEN 4.0
  WHEN diam> 5 AND diam<=10 THEN 7.5
  WHEN diam>10 AND diam<=15 THEN 11.0
  WHEN diam>15 AND diam<=20 THEN 14.5
  WHEN diam>20              THEN 18.0
END

Click OK

display_az

Check the Create virtual field box
Use the following inputs:

Output field name
display_az

Output field type
Integer (32 bit)

Output field length
10

Expression:

CASE
  WHEN az IS NULL THEN 45
  WHEN length(az)=1 THEN
 CASE
   WHEN az='N' THEN 45
   WHEN az='E' THEN 135
   WHEN az='S' THEN 225
   WHEN az='W' THEN 315
 END
  WHEN length(az)=2 THEN
 CASE
   WHEN az='NE' THEN 45
   WHEN az='SE' THEN 135
   WHEN az='SW' THEN 225
   WHEN az='NW' THEN 315
 END
  ELSE
 CASE
   WHEN substr(az, 1, 1)='N' THEN
     CASE
       WHEN substr(az, -1, 1)='W' THEN 315
       WHEN substr(az, -1, 1)='E' THEN 45
     END
   WHEN substr(az, 1, 1)='S' THEN
     CASE
       WHEN substr(az, -1, 1)='W' THEN 225
       WHEN substr(az, -1, 1)='E' THEN 135
     END
 END
END

Click OK

dtrsc

This time, do not check the Create virtual field box
Use the following inputs:

Output field name
dtrsc

Output field type
Whole number (integer - 64bit)

Depending on your QGIS version you may not see integer - 64bit unless you deselect virtual field. This will enter editing mode and add the field. You will need to save edits and exit editing mode after creating the field.
Expression:
```
  to_int(dtrsco/100)
```
Click OK

Click OK to close the properties.

Join Fields

Now that we have the needed fields, we’ll actually join witness_trees_42308 to corner_obs.

Open the Processing Toolbox and search for and open Join attributes by field value:

Use the following inputs:

Input layer
corner_obs

Table field
dtrsc

Input layer 2
witness_trees_42308

Table field 2
dtrsc

Join type
one-to-many
Check the box for Discard records which could not be joined
Click Run in Background, wait for it to run, then click Close.

Rename the newly created layer to something like witness_trees_42308_cartographic. Then add a filter by right-clicking on the layer and selecting Filter. For the filter expression use "observations_ptype" = 'P'.

Symbology

Next open the Properties for witness_trees_42308_cartographic and go to the Symbology tab:

At the top change Single Symbol to Categorized.
For Value select sp_class.
Edit the Symbol by clicking on it.
- Select Simple marker in the top box, then
- under Symbol layer type select Geometry generator.
- With Polygon selected as the Geometry type, enter the following in the box.
```
 buffer(project($geometry, diam_class*sqrt(2)*10, radians(display_az)), diam_class*10)
```
- Click OK to close.
Click Classify and five categories should appear.
- Select the null category and click the minus button to remove it.
- Right-click on the Hardwood record and select Change Color, then enter #bebada under HTML notation.
- Change the colors for Oak, Other Coniferous, and Pine to #ffffb3, #8dd3c7, and #fb8072 respectively. Click Apply to save progress.

Labels

To add labels, go to the Labels tab in the left menu. Change No labels to Rule-based labeling. Use the plus button at the bottom to add the following rules:

NE

Use the following inputs:

Description
NE

Filter
display_az = 45

Label with
sp
Select the Text section and change the Size to 6

Select the Placement section on the left

Select Offset from point
Then for Offset X,Y click the button on the far right and select Edit.

For the expression enter the query from below.

 CASE 
   WHEN "diam_class" = 4    THEN '1.7,-1.7'
   WHEN "diam_class" = 7.5  THEN '2,-2'
   WHEN "diam_class" = 11.0 THEN '2.5,-2.5'
   WHEN "diam_class" = 14.5 THEN '3.4,-3.4'
   WHEN "diam_class" = 18.0 THEN '4.3,-4.3'
 END

Click OK to close Expression String Builder

Click OK to close Edit Rule

NW

Use the following inputs:

Description
NW

Filter
display_az = 315

Label with
sp
Select the Text section and change the Size to 6

Select the Placement section on the left

Select Offset from point
Then for Offset X,Y click the button on the far right and select Edit.

For the expression enter the query from below.

 CASE 
   WHEN "diam_class" = 4    THEN '-1.7,-1.7'
   WHEN "diam_class" = 7.5  THEN '-2,-2'
   WHEN "diam_class" = 11.0 THEN '-2.5,-2.5'
   WHEN "diam_class" = 14.5 THEN '-3.4,-3.4'
   WHEN "diam_class" = 18.0 THEN '-4.3,-4.3'
 END 

Click OK to close Expression String Builder

Click OK to close Edit Rule

SE

Use the following inputs:

Description
SE

Filter
display_az = 135

Label with
sp
Select the Text section and change the Size to 6

Select the Placement section on the left

Select Offset from point
Then for Offset X,Y click the button on the far right and select Edit.

For the expression enter the query from below.

 CASE
   WHEN "diam_class" = 4    THEN '1.7,1.7'
   WHEN "diam_class" = 7.5  THEN '2,2'
   WHEN "diam_class" = 11.0 THEN '2.5,2.5'
   WHEN "diam_class" = 14.5 THEN '3.4,3.4'
   WHEN "diam_class" = 18.0 THEN '4.3,4.3'
 END

Click OK to close Expression String Builder

Click OK to close Edit Rule

SW

Use the following inputs:

Description
SW

Filter
display_az = 225

Label with
sp
Select the Text section and change the Size to 6

Select the Placement section on the left

Select Offset from point
Then for Offset X,Y click the button on the far right and select Edit.

For the expression enter the query from below.

 CASE
   WHEN "diam_class" = 4    THEN '-1.7,1.7'
   WHEN "diam_class" = 7.5  THEN '-2,2'
   WHEN "diam_class" = 11.0 THEN '-2.5,2.5'
   WHEN "diam_class" = 14.5 THEN '-3.4,3.4'
   WHEN "diam_class" = 18.0 THEN '-4.3,4.3'
 END 

Click OK to close Expression String Builder

Click OK to close Edit Rule

Click Apply and then OK to close out of properties.

Final Styling

Move the townships layer to just below witness_trees_42308_cartographic but above all the other visible layers.
Open its properties and go to the symbology tab:
- Change Single symbol to Inverted polygons
- Set Fill Color to white.
- Click OK.
From the geopackage, add the sections layer below townships and change the symbology to Fill style: No Brush.
Add an appropriate base layer.

Optional

This could be a georeferenced original plat map or a map service, etc. For this example I used Quick Map Services (this is a plugin you can add; if you do, go to settings > more services > get contributed pack) and chose ESRI Gray (light).

Your map should now look like something like what is below. The labels look messy, but should look better when we add the map to a print layout.

Print Layout

In the main menu click Project > New Print Layout. Click OK.
Right-click on page and select Page Properties. In the bottom right of the window under Item Properties:
- Change Size to Letter
- Change Orientation* to Portrait
Use the Add new map button on the left to add your map.
- Drag the edges of your map to meet the edges of the page on the left, right, and bottom.
- Leave room on the top making your map box square.
With your map selected, go to Item Properties and change the Scale to 55000.
From there you can add a legend, title, scalebar etc. Adding a legend depicting diameter size classes will have to be done manually. I usually do it in Adobe Illustrator but there are many other options including free software such as inkscape. You can download this legend template to give you a head start.

Check out this complete tree map for an example of a finished product.

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