Part I: Area data
Nominal Data Symbology for Area Data (qualitative)
Base Map data
- Create a folder lab6 in your local directory
- Start a new map file and add data: L:\labs\geog205\thematic_map\water_bodies.shp and river_lines.shp
- Save the map file as lab6.mxd in your local folder
Note attribute values in water_bodies DSCRPTN field: Gravel Bar, Lake, Wetland, River
- Symbolize as Categories the values in the DSCRPTN field, and rename the layer as Water Bodies in Table of Contents.
The large rivers appear as polygons. It is not necessary to differentiate large rivers from lakes. The rivers polygon value can be grouped with lakes as follows:
- Layer Properties -> Symbology tab, highlight both rivers and lakes, right-click the selection and Group.
- On the Symbology tab under the Label field, highlight the grouped value label and re-type the label as Water. Leaving the Layer Properties window open, click the Apply button and examine the results in the Table of Contents.
- Next, in the Layer Properties -> Symbology tab, ensure that the order in which the value labels appear is changed so that Water is at the top of the list by high-lighting the label of interest and using the promote/demote black arrows to move the label up or down. The position on this list affects their order in the Table of Contents and also in the Legend. OK
- Rename river_lines as Rivers and symbolize accordingly.
This layer was developed so that the center line of large rivers (polygons) is part of the line layer. The Fraser River is the large polygon river running north-west to south-east across the dataset. Zoom in on any part of the Fraser River to a display scale of about 1:60,000 to see these features. To hide the unnecessary centre line within large polygon rivers, change the drawing order so that Rivers draws beneath Water Bodies. Examine the results on the map – zoom to a display scale of about 1:150,000 and pan around.
Once you have finished symbolizing the water features you will save the symbology (your cartographic instructions) to a *.lyr file to be loaded into your next map: right-click Water Bodies –> Save as Layer File.. to your lab8 folder. Do the same for your rivers layer.
- Add Data: L:\labs\geog205\thematic_map\rshade
In the raster’s Layer Properties -> Symbology tab, change the stretch type to Minimum Maximum to lighten the shading.
You can see that this area encompasses mountains and a broad valley running north-west to south-east: the Rocky Mountain Trench. The mountains to the north-east of the Trench are the Rocky Mountains. The mountains to the south-west of the Trench are the Caribou Mountains. The entire dataset covers about 30 km from east to west. You can confirm this by using the Measure tool.
- Save changes to your map document.
- Turn off the shaded relief so that it does not draw in data view.
- Rename the Data Frame to Goat River.
- Add Data: L:\labs\geog205\thematic_map\forest.shp
First, you will symbolize this layer by the primary tree species codes found in the field SPC1_CD_1. This is a nominal category. Examine forest’s attribute table to see this field.
- In the Symbology tab, symbolize all the values in SPC1_CD_1 as Categories –> Unique Values using the SPC1_CD_1 field.
Select the Add all Values button and apply
Clearing Up Visual Clutter: Creating a Visual Merge
In forest -> Layer Properties –> Symbology tab, click on the Symbol heading and select Properties for all symbols. Make sure you have selected Properties for all symbols. Set outline to none. (Apply). This will also remove the internal boundaries of the map tiles (TRIM 1:20,000) that make up this data layer.
Examine the spatial data. With the polygon outlines removed, contiguous polygons of the same value (same primary tree species) are visually merged. Removing the outlines in this context has reduced visual clutter (unnecessary detail for the objectives at hand – the polygon outlines could be useful in another context).
The entire data set contains 18 tree species and subspecies. The following table explains the original codes in the dataset.
|AT||Trembling Aspen||Populus tremuloides|
|BL||Subalpine Fir||Abies lasiocarpa|
|CW||Western Redcedar||Thuja plicata|
|EP||Paper Birch||Betula papyrifera|
|HM||Mountain Hemlock||Tsuga mertensiana|
|HW||Western Hemlock||Tsuga heterophylla|
|PA||Whitebark Pine||Pinus albicaulis|
|PL||Lodgepole Pine||Pinus contorta|
|SB||Black Spruce||Picea mariana|
|SE||Englemann Spruce||Picea sp|
|SW||White Spruce||Picea glauca|
|SX||Spruce X||Picea glauca x sitchensis x engelmannii|
In order to simplify the colour palette, you will next group similar trees.
- In the Symbology tab, hold down the CTRL key and hi-light codes that you will be grouping into one class.
- Right-click your mouse over the selection -> Group. Under Label change the label as described below.
Continue to group & re-label the following:
|AC and AT||Broadleaf|
|S, SW, SE and SX||Spruce|
- Click Apply
- Save changes to the map file.
In order to improve map readability, a strategy for the order of the value labels in the Table of Contents would be to have the codes listed in order of decreasing area. The area can be guessed by the Count field (number of polygons per class).
- In the Symbology tab, if there are no values showing at this time, click on the Count field.
- Change the order from highest to lowest count. The number of polygons may not be a perfect way to guess total area for a species code, but it is close enough. If you notice discrepancies, you can change the order later.
- Click OK.
Examine the colours on the map and compare them to the codes in the Table of Contents. It can be easier for the map reader to notice the colour covering the largest area. If that colour is labelled first on the Table on Contents (and later the legend), the map reader quickly determines the meaning of the colour. If the map reader has to scan down the list, this will take longer.
There is one exception. Since this is a theme of tree species, the value for non-treed (<> ) should be moved to the bottom of the list. Change this label to Non-Treed and make it a pale gray fill with no outline. Examine the map data view.
Check your drawing order in the Table of Contents. The forest layer should draw beneath water bodies and rivers.
Choosing Colours for Nominal Data:
Colour Philosophy: The basic approach to symbolizing nominal categories is to use random colours: no colour within the group should advance (“pop” out). It is important that no two colours chosen for the symbol set are too visually similar. In a complex map with great detail this would make it difficult to tell polygons apart. First, because the human brain can’t retain the visual information long enough while looking from the map colour over the legend and back again to discriminate similar colours. Second, the colour of a polygon when surrounded by other colours experiences a colour shift which compounds the colour matching problem between the legend and the map polygon fills. A third complication arises as a colour on a computer monitor is flooded from behind by the screen’s light and that same colour on a paper print is created by pigments on a page reflecting light. A single colour can look different based on its medium. This may cause a computer monitor designed colour to look darker on the printed page (or paler) than intended, and may cause two or more colours to be difficult to visual discriminate on the printed map and match to the legend.
Do not use darker shades of one colour in a nominal symbol fill set (for example, multiple shades of green) since increasingly darker shades of one colour is used to symbolize magnitude (interval) data as “darker” means “more”.
For this exercise you will use polygon fills, do not use patterns.
Developing Meaning for your Colour Tints:
Colours can be associative, e.g. blue for water, green for forest. In the case of tree species, associative colours could be designed based on an understanding of the tree species themselves.
Western Cedar and Hemlock belong to the Rocky Mountain Trench’s Interior Rain Forest. Douglas Fir in the Trench in this context are usually part of the Interior Rain Forest. The rainforest is rich in tree vegetation and is much older than surrounding forests. Broadleaf is at the valley bottom, has a longer growing seasons, is wetter and flatter and its ecology tends to be more productive for some kinds of wildlife. Subalpine Fir is usually found in this context at high elevations immediately below treeline where the growing season is shorter and the climate drier and cooler. Pine is usually younger, and drier than the other tree species. Black spruce is usually found bordering wetland settings and is itself comparatively boggy. Paper Birch is similar to the broadleaf class.
As such, you can think of colour tints representing cool colours, or warm colours, more rich colours etc. to generally match the ecology of the trees. This can be for your first choices, and may not be necessary for all the species as you might run out of tints that you can tell apart on the map, and that you can match to the legend.
If you run out of ideas for tints, reserve using colours with greater saturation for areas of limited areal extent on the map. Visually, Douglas fir, Black Spruce, Paper Birch and Pine each take up smaller areas on this map. To test this, for each of these four species in turn, try turning the symbol colour to red so that you can easily see the species limited areal extent on the map. Then choose an appropriate colour. You choose the more saturated colour when you can no longer create a tint that contrasts with the other tints you have already chosen. Remember, the technique of giving a more saturated colour to smaller areas should not make the smaller area “advance” too much.
Here is a reminder of how to change the specific value of the colour:
In the Symbol Selector:
|Click the drop-down arrow beside the Fill Color, and click More Colors..|
|You will see the Color Selector.Click the black arrow and select the colour model HSV.
You may now adjust an individual colour.
Note that as you change the HSV numbers, the preview colour box on the left changes.
Ensure the percentage of gray for Non-Treed (the V of HSV) is 97%
The number of colours you will now design has been reduced from 18 to 9. The theme is dominant tree species.
Proceed now to assign tints to the 9 classes. Ensure you:
- can distinguish the tints (you can tell them apart visually),
- can match a colour fill on the map to its patch on the Table of Contents
- do not allow any colour to “advance” – that is, no colour is dominant.
If you find that a colour is visually dominant, you might find that assigning it to a tree species that covers a small area on the map may improve the visual balance.
- You can save this map as nominal.mxd
- Save your map document.
Draping Nominal Symbology over Shaded Relief:
- First, turn the forest layer off in the Table of Contents, and turn the shaded relief rshade on. As you examine the shaded relief you will see shades of gray.
The following illustration shows a strip of the shaded relief A. One colour is placed over that shaded relief in B. The same colour is given a transparency of 40% in C.
|The gray value of the colour sample in B varies throughout C.
You should be aware that drapes create variation within your original colour choice.
- Turn Forest back on so that it draws.
- Create the drape: Forest’s Layer Properties -> Display tab, set the layer’s Transparency to 40%.
Examine how much variation now exists within any one of your chosen colours.
- Remove the transparency value – ensure it is set back to 0 in the forest layer.
- Turn off the shaded relief so that it does not draw.
- Save the map file to norminalhsd.mxd under you lab8 folder.
Symbolizing Areas by Quantities
- Start a new map, toggle back to the Data View, and add data from your lab8 folder:
water bodies.lyr and rivers.lyr
- Save your map document to your mylab8 folder as quantities.mxd
- Add Data L:\labs\geog205\thematic_map\forest.shp
- Open its attribute table and note the two fields. SPEC_CD_1 represents the primary tree species in the polygon. Age_1 represents the age in years of that polygon.
- Symbolize Age as Quantities -> Graduated colors
- Select an appropriate color ramp and apply
You will see numbers from 0 up to 450 years in the Table of Contents.
Look for pattern in the map. Can you determine the age of the polygon on the map visually? You can query the polygon with the Identify tool. To improve the visual quality of the map, you should remove the polygon outlines (as in section 1). It also removes the unwanted map tile edges. Try this now.
While magnitude is shown as increasingly dark colours, there are too many values in the dataset resulting in too many colours. It is not possible to match a colour to the legend, nor discriminate between the numerous colours on the map. Plus, the gaps in the data values are not illustrated properly as the colour change is continuous. Remove the 0 value colour patch from the Symbology tab. This doesn’t improve visual quality.
You could improve the discrimination by changing from a one-colour blend to a two-colour blend. Try a suitable two colour (bichromatic) ramp if you haven’t already.
Apply this to the map. Examine the results.
What will prove to be helpful will be a generalization of the range of data values. To do this, you will next classify the age values.
- In the Properties -> Symbology tab (it should still be active)
- What classification method is being used?
- Click the Classify button and examine the histogram. What is a histogram?
Since a polygon with the value of 0 is a treeless polygon, you will now exclude it from the classification:
- Click the Exclude… button and enter the following expression into the query window, by double-clicking on AGE_1 and single clicking on = and then typing 0
“AGE_1″ = 0
- Click OK, return to the map and examine the results of this classification on the map. [The default palette was a two-colour blend (yellow to brown)].
Notice the range of class values in the table of contents (for example, all years from 1 to 53 are grouped into one class, and assigned the colour pale yellow). (these numbers may not exactly match yours) Notice the upper value of the class ranges: ~ 53, 125, 187, 246, 450.
Keeping the same palette experiment with all the classification schemes discussed in lecture: Natural Breaks, Geometric, Equal Interval, and Quantiles. You should also experiment with changing the class number from 5 to 7. You will leave the map in Data View. Make sure you have removed the polygon outlines.
Lastly, create User-Defined Classes using the following classification scheme:
|1||1 – 20 Years|
|2||21 – 40 Years|
|3||41 – 60 Years|
|4||61 – 100 Years|
|5||101 – 140 Years|
|6||141 – 250 Years|
|7||251 + Years|
- Save this as age_class.mxd
Part II: Point Data
- Open a new map document and add the following layers:
L:\labs\geog205\bc\bccities.shp, bchwy.shp and bcbound.shp
- Symbolize main and local roads in bchwy (value = road.main, road.local) and make the roads a pale gray
- Symbolize the bcbound layer as hollow with a dark gray outline
- Symbolize the polygon feature class bccities with a gray fill and medium gray outline
- Save the map document as lab6_point.mxd (you can create the new folder in the save window).
The layer student_towns has an attribute table field called Students – the number of UNBC students (in 2000) from that town (we should update this for more current numbers!).
- Examine the attribute table for student_towns and locate the Students field and the City field ( name of the town)
- Query a few of the feature points with the Identify button to confirm the name, and number of students.
The attribute table for student_towns contains many fields. In order to reduce the clutter in the attribute table and to focus on the task at hand, you are going to hide some of the extra fields. To temporarily turn off some of the attribute table fields:
- Go to the student_towns -> Layer Properties -> Fields tab. All visible fields have a checkmark.
- Click the Clear All button to remove all the checkmarks, and place a checkmark for the following three field names: City, Students, and Latitude
Re-examine the attribute table. You should now see that all the non-checkmarked fields are hidden from view. Save changes to your map document. The attribute table remains unaltered, all its data remains on the hard drive and the instructions to hide the fields from your view are stored in your map document.
Examine the attribute data more closely:
- In the attribute table, hold your mouse directly over the field name City and right-click. You now see the Field Menu.
- Click Sort Ascending to re-order the city names alphabetically. You can scroll down the field to see the names.
Q: Which are the towns/cities with the highest number of UNBC students?
- Sort the Students field in descending order. The Latitude field gives the “northerness” by its Latitude.
- Sort the Latitude field in order to see which are the most northern cities and towns of origin for UNBC students.
Q: Using all three columns: Of the top 10 cities or towns for number of UNBC students, which is the most northern?
Scanning attribute values in a table is informative, but a spatial representation of the locations, place names and magnitude of UNBC enrolment on a map is a powerful graphical method of data representation.
Range Graded & Graduated Symbols
The remainder of this lab will be spent in designing a map that incorporates ‘graduated’ symbols. When working with graduated symbols consider the following:
- Symbol size measured in area should reflect the values being represented.
- All symbols should be visible. The smallest symbols must be bigger than dots.
- There should be some overlap to give the impression of concentrations in some parts of the map.
- Where there is overlap, the smaller symbols should retain their outline to give the visual impression of being on top
- The circle is the standard graduated symbol, but in some cases, other shapes may work better.
For ARCGIS Graduated Symbols (Range Graded):
- If it is necessary to class or group the values (ARCGIS graduated symbols), values should be grouped for maximum similarity within the classes and maximum variation between the classes. Class boundaries, should where possible, be round numbers (10, 50, 100 etc).
ARCGIS (ArcMap): knowing the difference between literature terminology and software terminology
- Graduated symbols are known as Proportional symbols in the ARCGIS software
- Range graded symbols are known as Graduated symbols in the ARCGIS software.
- Memory tip: range graded = graduated
- For the remainder of the lab, ARCGIS terms will be used
- Set the Data Frame Properties -> General tab Reference Scale to 1:10,000,000
- In student_towns -> Layer Properties-> Symbology tab, and click on Quantities.
- Click Graduated Symbols (remember that this selection represents the range -graded symbols from lecture)
- Click the dropdown list for Value Field and choose Students.
- You will find these symbols are too small, and may be a poor color.
- To change, change Symbol Size range, set the upper range to 76. Click OK.
Arcmap ‘graduated’symbols (described as range graded in lecture)
Let’s evaluate what the software has done. To do this, focus on two cities: Prince Rupert and Quesnel. To focus in on these two locations in the map, go to student_towns -> Layer Properties -> Definition Query tab. Whatever attribute value is found to be true in the query written here will be the feature drawn on the map. All attribute values that are false are hidden from view. Copy the following query and paste it into the query window. Make sure you copied the entire query and did not miss the ” at the beginning. You can type ” into the query yourself if needed.
“CITY” = ‘PRINCE RUPERT’ OR “CITY” = ‘QUESNEL’
- Click OK.
Turn on student_towns labels. To remind yourself of the number of students from each town, you can add the Student value to the label as follows:
- In student_towns -> Layer Properties -> Labels tab, click the Expression button.
- Copy and paste the following expression into the expression window. Make sure you copied the initial [at the start. You can type the [into the expression yourself.
[CITY] & ” – ” & [STUDENTS]
- Click OK
If Quesnel has two times the student enrollment of Prince Rupert, then the area of the circle for Quesnel should be two times the area of Prince Ruport . Does this appear to be the case? It may be easier to evaluate this if the shape were a square and not a circle.
- Return to the Layer Properties -> Symbology tab and click on the Template button. Choose the green square.
Graduated symbols group the quantitative value into classes (range graded). All values within that class range are drawn on the map with the same symbol. You cannot tell the value of the individual map circle symbols, you can only match the circle to the range symbol in the legend to determine the possible range of values.
- What is the class range for Prince Rupert?
- Does the circle/square for Prince Rupert match the circle in the Table of Contents for that class range?
- What is the class range for Quesnel?
- Again, does the circle for Quesnel on the map match the circle in the Table of Contents for that class range?
Graduated Symbols (range graded symbols) select one symbol size for the entire range of values for each class, and as a result, you cannot determine the magnitude of individual town/city values from the map symbol, you can only match the town/city symbol on the map to a class range.
Arcmap ‘proportional’ symbols (described as ‘graduated’ in lectures)
- Change the method to Proportional, Value field to Students, Unit to unknown and Min Value to 20.
Does the area for Quesnel appear to be 2 times the area of Prince Rupertl?
Proportional symbols (graduated symbols) precisely represent the magnitude of the value.
Let’s examine all the BC towns and cities again:
- Remove the query in the Layer Properties -> Definition Query tab. OK.
- Turn the labels off, and in the Layer Properties -> Labels tab -> Expression button change the labelling expression back to [CITY]
- On the Symbology tab, change the Min Value to 4 , and the number of symbols for the legend to 5. OK
With ARCGIS Proportional Symbols (graduated symbols), the area of the map symbol does represent the specific value for that map symbol, but there are a lot of sizes to visually interpret. Experiment with the Min Value, for example and try 6 or 8. Change the value back to 4.
Having experimented with both techniques, you will now save you map document as lab8_proportional.mxd.
Remember that the Reference Scale makes a huge difference on the sizing of the symbols on the map. You have it set at 1:10,000,000. If for example, you had begun the map with a 1:2,000,000 reference scale, then the sizes would be very different and you would choose different values in the symbology tab to achieve the correct cartographic look for the circles. As you design your proportional symbol map, you have the option of changing the reference scale (you don’t have to). Remember to achieve the cartographic principles discussed in lecture for this symbol technique.
STOP! What is the correct term in the literature for ArcGIS Arcmap’s proportional symbols?
- You should be able to identify a range graded symbol map when you see it (literature term).
- You should be able to identify a proportional symbol map when you see it (literature term).
- You will be questioned based on the terms from literature.
- You should be able to state the ArcGIS equivalent term.
Adding Text Labels
When you turn on the labels for this layer, you can see that there are too many labels.
First, change the position of the label relative to the feature point as follows:
- Layer Properties -> Labels tab -> Placement Properties button.
- Click Place label on top of point
You can begin to pare down the number of labels by labelling only the cities/towns in northern BC. Open the attribute table and note that each city/town has a latitude value (Lat).
Determine the latitude just south of Quesnel as follows:
- Data Frame Properties -> General tab, change the Display Units to Degrees, Minutes and Seconds.
- Locate Quesnel on the map, and hold you mouse over that location while you read the coordinate display (ignore the decimal places on the seconds). Note the use of the degree symbol instead of d for degrees.
- Next, change the Display Units to decimal degrees and write down that value for Quesnel.
Create a query within the labelling expression that limits the CITY labels to those with a decimal degree value greater than just south of Quesnel as follows:
In student_towns -> Layer Properties -> Labels tab -> Expression button, the expression is presently [CITY].
- Place a checkmark for Advanced Expression and delete everything there.
- High-light the entire expression in the Expression window, and delete it (right-click selection – Delete)
- Copy and paste the following expression into the Expression window:
Function FindLabel ( [CITY], [Lat])
if [Lat] > 52 then
FindLabel = [CITY]
- Click OK and OK again to return to the map to view your results.
- Adjust the label text size (for example, at a reference scale of 1:10,000,000 you could try 6 points).
When you right-click a feature layer in the Table of Contents and turn Label Features on as you have done, you are creating Dynamic Labels. Dynamic Labels are being read directly from the attribute table. The default setting for the software is dropping conflicting labels. You have no control over which of the northern cities are being labelled. You can force all labels from Quesnel north to draw as follows:
- Layer Properties -> Labels tab -> Placment Properties button -> Conflict Detection tab and place a checkmark at the bottom for Place overlapping labels.
Examine the results on the map. This creates a lot of overlapping labels.
There is still a great deal of label clutter. You can reduce the number of labels by labelling only large cities/towns in the north. Expose the hidden field CSD_POP96. Examine these population values in the attribute table. You can reduce the label clutter by modifying the label expression to include only those labels for cities with a population greater than 5000.
- First, see if you can identify the population restriction from the following query, then replace the label expression with the following query (delete the entire query in the Expression window, then copy/paste in the following):
Function FindLabel ( [CITY], [Lat], [CSD_POP96], [STUDENTS])
if [Lat] > 52 and [CSD_POP96] > 5000 then
FindLabel = [CITY] & vbnewline & [STUDENTS]
The abover labelling expression will show the city name and the student numbers for the clity that have latditude greater than 52 degree and population are greater than 5000. To further clarify the labels, you will next place a “halo”, or thin white band around each letter so that its contrast with the background features is improved:
- In student_towns -> Layer Properties -> Labels tab, click the Symbols button, next, the Properties… button and then the Mask tab. Click on Halo and set the size (thickness) to 1 or 0.5 points. Keep clicking OK to finish.
The goal of this assignment is to produce a finished map showing the distribution of UNBC students, using the proportional symbols (i.e. no range graded classes). This should be designed with:
- Letter page format 8.5 x 11 “
- Colours permitted
- Legend with a suitable sample number of symbol sizes
- Suitable background layers for context if necessary (e.g. roads, BC boundary from (N:labsgeog205bc). Background layers not required in legend if explained on the map
- Label the city name and student number for the city locations that have student number greater than 50
- North arrow might be optional
- Scale bar
- Suitable title and you name and date.
Note that ancillary information should be fitted around the map, such that the map has visual prominance and area, and the ancillary information is secondary.
The map area itself should fill the page as much as possible, to enable maximum details to the symbols.
To save the map image, you can export the map to JPG files
- In ArcMap, go File->Export Map, set file type to JPG and save it in your local folder
- In ArcScene, go File->Export Scene->2D, set the file type to JPG and save it in your lcoal folder.
- To save the map in PDF, go File->Export Map, set file type to PDF and save it in your local folder.
Save the map in .PDF format (NOT .mxd) and send to Ping or Jessica by 12:00pm Tuesday Nov. 15th