United States

Department of

Agriculture

Forest Service

Southern 

Research Station

General Technical 

Report SRS–135

UrbanCrowns: 

An Assessment and 

Monitoring Tool for Urban Trees

Matthew F. Winn, Philip A. Araman, and Sang-Mook Lee
Authors:

Matthew F. Winn, Forestry Technician, and Philip A. Araman, Team 

Leader, U.S. Forest Service, Southern Research Station, Blacksburg, 

VA 24060; and Sang-Mook Lee, Postdoctoral Researcher, Virginia 

Polytechnic Institute and State University, Department of Electrical and 

Computer Engineering, Blacksburg, VA 24061.

February 2011 

Southern Research Station 

200 W.T. Weaver Blvd. 

Asheville, NC 28804

Product Disclaimer

The use of trade or firm names in this publication is for reader information and does not imply 

endorsement by the U.S. Department of Agriculture of any product or service.
UrbanCrowns:

An Assessment and 

Monitoring Tool for Urban Trees

Matthew F. Winn, Philip A. Araman, and Sang-Mook Lee

iii

Contents

Introduction ....................................................................................................................................... 1

Photographing the Tree .................................................................................................................... 1

Field Measurements .......................................................................................................................... 2

Software Installation ......................................................................................................................... 4

Program Overview ............................................................................................................................ 4

Input Parameters .............................................................................................................................. 5

Image Reference Lines...................................................................................................................... 5

Image Assessment and Output ......................................................................................................... 6

Using the Database ............................................................................................................................ 8

Crown Transparency ........................................................................................................................ 9

Crown Volume ................................................................................................................................... 9

Conclusion ....................................................................................................................................... 10

Literature Cited............................................................................................................................... 10

Page

Abstract

UrbanCrowns is a Windows®-based computer program used to 

assess the crown characteristics of urban trees. The software 

analyzes side-view digital photographs of trees to compute 

several crown metrics, including crown height, crown diameter, 

live crown ratio, crown volume, crown density, and crown 

transparency. Potential uses of the UrbanCrowns program include 

monitoring individual tree growth over time, detecting disease or 

insect damage in early stages, and providing data to quantify tree 

benefits such as carbon sequestration, rainfall interception, energy 

conservation, pollution removal, and oxygen production.

Keywords: Crown characteristics, crown volume, monitoring, 

transparency, urban forestry, urban trees.

Introduction

Trees are important assets to the urban environment. In 

addition to providing aesthetic, social, and economic values 

to urban communities, they provide many environmental 

benefits as well. They improve air quality by reducing 

temperatures, lowering volatile organic compound (often 

referred to as VOC) emissions, producing oxygen, and 

removing harmful pollutants from the air (Nowak and others 

2006). They can improve water quality by intercepting 

and filtering rainfall, thus reducing urban runoff and the 

pollutants they carry (Nowak and others 2007). Strategically 

placed trees can also reduce heating and cooling energy use 

by providing shade in the summer and windbreaks in the 

winter (Heisler 1986).

The urban environment, however, can often produce added 

stresses to these trees. Soil compaction, limited root growth, 

and groundwater contamination are just a few of the factors 

that can influence tree growth and vigor (Roberts 1977). 

Only when urban forests are healthy and free from serious 

hazards, do they add value to communities. Unhealthy, 

hazardous trees diminish urban forest value and create 

liabilities for tree owners. For this reason, trees should be 

monitored periodically to permit early detection of disorders 

and hazards so that appropriate actions can be taken to 

maintain forest health, safety, and value.

Current assessment methods for urban trees use a 

combination of ground-based measurements and visual 

estimation of tree features. A large emphasis is placed on 

tree crowns, since crown size, shape, and density can be 

good indicators of overall tree health. This is also where a 

good portion of the visual estimation takes place because 

of the difficulty in accessing the crown from ground level. 

Visual assessment of tree characteristics often produces very 

subjective results that vary by surveyor, tree species, weather 

conditions, etc. For more accurate tree assessments, a more 

objective approach is needed. 

The Forest Service, U.S. Department of Agriculture has 

developed a computer software tool to facilitate urban 

tree assessment and monitoring. The software, called 

UrbanCrowns, can be used by anyone with or without a 

background in urban forestry to analyze urban tree crown 

characteristics using only a digital photograph and a few 

easily collected field measurements. The program, which 

supports both broadleaf and coniferous tree analysis, can 

be used in conjunction with monitoring programs to detect 

changes in crown conditions and can assist with quantifying 

tree functions and benefits. UrbanCrowns can also be a 

useful tool for heritage tree programs, where trees are 

considered to be of special importance due to their age, size, 

type, or historical significance.

Analyzing an urban tree using the UrbanCrowns program 

is a simple procedure. First, a digital photograph is taken of 

the subject tree and several field measurements are collected 

from the photo location. Field measurements include the 

horizontal distance to the tree and the vertical angles to the 

top and base of the tree. The photograph is then uploaded 

into the program and a series of reference lines are drawn 

on the image. The lines are used to scale the image and 

delineate portions of the crown. The image is then processed 

and returns to the user the following crown measurements: 

height, diameter, live crown ratio, volume, density, and 

transparency. The results of the analysis can then be printed 

or saved to a database.

Photographing the Tree

The first step in the analysis procedure is to acquire 

a digital photo of the subject tree. This image will be 

used to perform all analyses within the program, so the 

quality of the photo can directly affect the accuracy of the 

computations. By using some forethought and following 

some simple photographic guidelines, the user can obtain 

UrbanCrowns: An Assessment and 

Monitoring Tool for Urban Trees

Matthew F. Winn, Philip A. Araman, and Sang-Mook Lee
2

the best possible results from the analysis software. A basic 

digital camera is all that is needed and image resolution is 

not critical. However, avoid using attachable wide angle or 

telephoto lenses.

First, determine the best time and location for acquiring 

a photo. Be sure to photograph trees after full leaf out 

and before leaves start shedding in the fall. Midday is the 

best time to photograph because the sun is high in the sky 

and glare is reduced. Never shoot directly into the sun. 

The weather can also affect image quality so attempt to 

photograph on sunny days with high visibility and low wind.

For the most accurate estimate of crown transparency, 

minimize the amount of background vegetation visible 

through the tree’s crown as well as any structures such as 

buildings or light poles. The software cannot distinguish 

between crown foliage and background vegetation and 

may not be able to filter out urban structures, depending 

on the color contrast. It is not necessary (nor possible in 

most situations) to obtain a photograph where there is no 

background interference, but the less interference in the 

photograph, the more accurate the transparency estimates. 

Choose a distance from the tree that allows the full tree 

(stem and crown) to appear in the image, and if the vantage 

point is far from the tree, zooming is permissible. There 

should be no obstructions (buildings, other trees, etc.) 

between the camera and tree that block the view of the 

crown or tree base. Pictures can be taken in portrait or 

landscape format, but be sure to center the tree image both 

vertically and horizontally in the viewfinder.

Urban trees often reside near buildings, roads, and other 

urban structures which can make it difficult to fulfill all of 

the photographic requirements. In those cases, determine the 

best photo location under the circumstances, but recognize 

that the accuracy of the computations may be diminished. 

Be wary of the surroundings and never photograph from a 

street or other unsafe environment.

Examples of correctly photographed urban trees are 

shown in figure 1. Notice that in all photos, the tree image 

is centered both vertically and horizontally, there are no 

obstructions between the camera and the tree, and a large 

portion of the crown is free from background interference. 

Figure 2 shows examples of poorly photographed trees. In 

the first photograph (fig. 2A), a building is obstructing the 

view of the bottom portion of the tree. Figure 2B shows 

a tree containing too much interference from background 

vegetation. In addition, the tree is not centered vertically 

in the photograph. Figure 2C shows a photograph taken 

under poor lighting conditions. The camera should never be 

aimed directly at the sun. Also, the photo does not include 

the entire tree stem. Assessing low-quality photographs with 

UrbanCrowns will produce inaccurate results.

Field Measurements

In addition to photographing the tree, several tree 

measurements must also be collected from the photo 

location in order to scale the photograph within the program 

(fig. 3). Without these additional inputs, the program 

will not function correctly. First, measure the angles (in 

degrees) to the top and base of the tree using a clinometer 

Figure 1—Examples of correctly photographed urban trees. 
3

or other vertical angle measuring device. Be sure to record 

whether the angle is negative or positive. Next, measure the 

horizontal distance to the lower stem of the tree using a laser 

rangefinder or tape measure. There are several instruments 

on the market that measure both horizontal distance and 

vertical angles from a single location, and though they 

cost a bit more than traditional measuring tools, they can 

significantly reduce the data collection time at each tree.

In addition to the angle and horizontal distance 

measurements, it is recommended (though not required) 

that several other pieces of information be recorded as well. 

If the tree will be monitored periodically, it is necessary to 

know the exact location from which the photograph was 

taken. Any deviation from the original photo location may 

produce non-comparable results. By measuring the azimuth 

to the tree with a compass and combining that with the 

Figure 3—Required field measurements taken from photo location. 

Figure 2—Examples of poorly photographed urban trees. 
4

horizontal distance measurement collected earlier, it will be 

possible to return to the original photo location in the future. 

Other useful information worth recording is the tree species, 

location of tree, weather conditions, photo date, and any 

comments worth noting. This information can be stored in 

an UrbanCrowns data file for each tree.

Software Installation

Before installing the UrbanCrowns software, be sure that 

the computer is running Microsoft® Windows® XP or later. 

The program may run on older versions of Windows® but 

has only been tested on XP. The software also requires the 

use of the Windows® .NET Framework 2.0, which is a 

Microsoft® library package for Windows® programming. 

During installation, the program will check the computer to 

see if this version is installed. If not found, the installation 

program will automatically download and install the 

necessary files from the Microsoft® Web site. For this 

reason, the computer should be connected to the internet 

during the installation process.

The UrbanCrowns installation files can be downloaded at 

the following address: http://www.srs.fs.usda.gov/pubs/

software/urbancrowns.zip. Unzip and save the contents 

of the “urbancrowns.zip” file to the computer’s desktop. 

Navigate to the desktop and double-click the “setup.

exe” file. A screen will appear that reads “Welcome to the 

UrbanCrown Setup Wizard”. Click the “Next” button to 

continue. The following screen prompts for the folder where 

the program is to be installed (fig. 4). Install to the default 

folder or select a new location by clicking on the “Browse” 

button and selecting a new folder. Make sure there are at 

least 27 megabytes of free disk space available at the chosen 

location. To see how much space is available on the hard 

drive(s), click on the “Disk Cost” button. At the bottom of 

the screen, specify who will have access to the program. To 

limit access to the current user, select the “Just Me” radio 

button, or select “Everyone” to allow access to all users. 

When finished, click the “Next” button to continue. The 

next screen is the installation confirmation screen. Click the 

“Next” button to proceed with the installation or the “Back” 

button to change the installation configuration. To abort the 

installation, click the “Cancel” button. After a short period 

of time, a confirmation screen will appear indicating that 

the installation was successful. A shortcut to the program 

labeled “UrbanCrown” will be placed on the computer’s 

desktop.

Program Overview

To begin using the program, double-click on the 

UrbanCrowns icon located on the computer’s desktop. The 

UrbanCrowns software comprises two main windows: the 

Tree Image window and the Data Control window (fig. 5). 

The Tree Image window contains the uploaded photograph 

of the tree to be analyzed. All image controls are located in 

this window, including: opening, rotating, scaling, printing, 

and saving the image. The Data Control window is used for 

inputting data, initiating assessment, viewing output, and 

managing the database. Within the Data Control window, 

there are two tabs: Information and Assessment. The 

Information tab is where the user enters the input parameters 

for the tree image and includes: tree ID, tree species, photo 

location, photo date, azimuth to tree, horizontal distance, 

angle to the top of the tree, angle to the base of the tree, and 

user comments. The Assessment tab is where the results 

of the analysis are displayed once the image is processed 

and includes: tree height, tree length, crown height, crown 

diameter, crown ratio, crown density, crown transparency, 

and crown volume. Since crown measurement terminology 

and definitions vary, it is important to know how the output 

parameters are defined with respect to UrbanCrowns. The 

terminology used in the program’s output is defined below:

•	 Tree height—The vertical distance from the base of the 

tree stem to the highest point of the tree crown 

•	 Tree length—The distance from the base of the tree to 

the top of the tree following the lean of the main stem

•	 Crown height—The vertical distance between the 

lowest point of the crown and the highest point of the 

crown

•	 Crown diameter—The horizontal distance between the 

leftmost and rightmost regions of the crown

•	 Crown ratio—The vertical crown height divided by the 

vertical tree height

•	 Crown transparency—The amount of skylight visible 

through the crown expressed as a percentage of the total 

2-dimensional tree crown area

•	 Crown density—The complement of transparency, 

or the amount of crown structures blocking light 

(calculated by subtracting transparency percent from 

100 percent)

•	 Crown volume—Volume of all tree structures (leaves, 

branches, twigs, and stem) occurring within the crown

Figure 4—UrbanCrowns setup window prompting for installation 

location and user access.
5

Input Parameters

To load a tree image into UrbanCrowns, click on the yellow 

folder icon located on the left side of the menu bar in the 

Tree Image window. Navigate to the folder where the image 

is stored, select the desired image, and click the “Open” 

button. If the image needs to be rotated, select the “View 

Control” pull-down menu, then select “Rotate Left” or 

“Rotate Right” as needed.

Once the image has been opened and rotated, the next 

step is to enter the field measurements and other tree 

information collected when the tree was photographed. In 

the Data Control window, select the Information tab and 

enter the input parameters for the tree. Certain input fields 

require values while other fields are optional. Required 

fields include: tree ID, horizontal distance, top angle, and 

bottom angle. Optional fields include: species, location, 

photo date, azimuth, and comments. Figure 6 shows sample 

input for a sugar maple (Acer saccharum). In this example, 

the tree ID (a unique identifying label created by the user) 

is “SugMap1”. The horizontal distance is 74.0 feet. The 

vertical angle from the camera location to the top of the tree 

is 21.5 degrees and the angle to the base of the tree is -7.0 

degrees.

Image Reference Lines

In addition to the input data, several reference lines 

also need to be drawn on the tree image before it can be 

processed (fig. 7). To have each of the lines displayed on 

the image after drawing them, select the “Show drawings” 

option under the “View Control” pull-down menu. The first 

line (shown in yellow) extends from the base of the tree to 

the top-most portion of the crown and follows the lean of 

the stem. This line, combined with the angle and horizontal 

distance measurements entered earlier, is used to scale the 

photograph (determine the actual area represented by each 

pixel). To draw the line, select the Tree Length button, 

which is just to the right of the “View Control” pull-down 

menu in the Tree Image window. Click on the base of the 

tree and drag a line to the top of the tree following the lean 

of the stem.

Figure 5—Screen capture of the UrbanCrowns program showing the Data Control window on the left and the Tree Image window on the right. 
6

The second reference line (shown in blue) is a polygon 

drawn around the entire tree crown and is used to compute 

crown volume. To begin, select the “Crown Region” button, 

which is just to the right of the “Tree Length” button. Click 

somewhere outside of the tree crown and drag a line around 

the crown back to the starting point. Release the mouse 

button to close the polygon. This is a rough outline so it does 

not need to be drawn tightly to the edge of the crown. Once 

the rough outline has been drawn, right click on the image 

to go into editing mode. While in editing mode, the outline 

will change from blue to red. For any portion of the tree that 

has background interference (other trees, grass, buildings, 

etc.), drag the nodes of the outline tight against the edge of 

the crown. To add a node, click anywhere between existing 

nodes. The outline does not need to hug the crown in areas 

where there is no background interference (sky). When 

the image is processed, the program will shrink-wrap the 

selection region so that it conforms to the unobstructed 

outline of the crown.

The final reference line (shown in pink) is drawn around the 

portion of the crown that is free from background vegetation 

or other obstructions. This is the area that will be used by 

the program to compute crown transparency and density. 

First, select the “Transparency Measurement Region” button 

located to the right of the Crown Region button. Next, click 

near the outside of the crown where there is no background 

interference. Continue clicking around the unobstructed 

portion of the crown until the starting point is reached. Click 

on the first point to close the polygon. Inspect the polygon 

to be sure that no background vegetation is selected. If 

necessary, reclick on the image to redraw a new polygon. 

No editing is necessary for this outline since no background 

vegetation is included in the selection region. Similar to the 

crown selection region, the program will contract the line to 

the edge of the crown when processed.

In the rare case that the entire tree crown is free from 

background interference (meaning nothing but sky in the 

background), UrbanCrowns allows drawing of a single 

outline around the tree crown instead of two outlines (fig. 

8). This one outline will be used to estimate both crown 

transparency and volume. To use a single outline, check 

“Use one outline” under the “View Control” pull-down 

menu. Select the “Crown Region” button and draw the 

outline around the tree crown. Since there should only 

be sky in the background, no editing of the polygon is 

necessary, except at the intersection of the crown and the 

stem. Make sure that only the stem section that falls within 

the crown is selected.

Image Assessment and Output

Before assessing the tree image, verify that “Auto 

Threshold” is checked under the “Method” menu item in 

the Data Control window. This is the default setting and 

shouldn’t be changed. To process the tree image, click 

Figure 7—Reference lines drawn on the tree image to scale the 

photograph as well as delineate the crown and transparency regions.

Figure 6—The Information tab of the Data Control window showing 

sample input for a sugar maple tree.
7

on the “Assess” button in the bottom right corner of the 

Data Control window. The results of the analysis are 

then displayed under the Assessment tab (fig. 9). For this 

example, the results are as follows: tree height and length 

are 38.2 feet, crown height is 35.6 feet, crown diameter is 

34.5 feet, crown ratio is 93 percent, crown density is 89.9 

percent, crown transparency is 10.1 percent, and crown 

volume is 17,300 cubic feet. If the “Show result” option is 

checked under the “View Control” pull-down menu, a popup window will also appear that contains a contour image 

of the tree (fig. 10). The contour image shows the shrinkwrapped crown assessment areas that were used in the 

analysis.

To save a copy of the image (including reference lines), 

click on the “Save Image” icon located in the upper left 

corner of the Tree Image window. Choose the location and 

image format, then click the “Save” button. Once saved, a 

report will be displayed showing all of the input and output 

parameters for the analysis (fig. 11). The report can be 

saved to a text file by clicking on the “Save to a File” button 

or copied to the computer’s clipboard by clicking on the 

“Copy to Clipboard” button. To save a picture of the contour 

image, select the checkbox for “Save Contour Image” prior 

to clicking the “OK” button. To print a report that shows 

the tree image (including reference lines) along with input 

Figure 10—Post-assessment contour image showing the shrink-wrapped 

crown assessment areas.

Figure 9—Post-assessment results for the sugar maple example.

Figure 8—Single outline used to determine crown transparency and 

volume for a tree image containing no background interference.
8

parameters and assessment results, click on the printer icon 

in the upper left corner of the Tree Image window. 

Using the Database

UrbanCrowns can store all of the input and output from an 

assessment in a database. Once in the database, a tree can 

then be imported back into the program with the original 

input and reference lines. To save an assessed tree to the 

database, first create a new database by clicking “Database” 

and then “New” in the Data Control window. Choose a 

name and location for the database and click the “Open” 

button. To open an existing database, select “Open” under 

the “Database” menu item. All databases will have the 

file extension “.cdb”. Under the “Record” menu, select 

“Append” to add a new record to the database, “Update” to 

change an existing record, or “Delete” to delete the record 

from the database. Once a database has been modified, save 

the database by selecting “Save” in the “Database” menu. 

To create a text file showing all of the information housed in 

the current database, select “Record” then “Log” in the Data 

Control window.

To import a tree from the database, first make sure the 

desired database is open. Then click on the “Import” button 

in the bottom left corner of the Data Control window. 

A window will appear showing all trees stored in that 

database (fig. 12). When the mouse cursor is placed over 

Figure 11—Report generated by UrbanCrowns showing input parameters 

and assessment results.

Figure 12—UrbanCrowns window showing trees available for import from current database as well as information stored with selected tree.
9

the thumbnail picture of each tree, the information stored 

with that tree will be shown in a preview window just to the 

right. Double-click on the desired tree to import it into the 

program. 

Crown Transparency

The program computes crown transparency by analyzing the 

relative color of each pixel within the transparency selection 

region. Each pixel is classified as either background (sky) 

or tree structure (stem, leaves, branches, etc.). Transparency 

is then calculated as the percentage of pixels within the 

selection region that are classified as background.

Transparency is one of the key measurements used to 

assess the health of urban trees. An increase in transparency 

from one year to the next can indicate that the tree is 

experiencing stress, which in turn can reduce growth 

potential, vigor, survivability, and reproductive potential. 

Some causes of increased crown transparency include: 

insect infestation, disease, environmental stresses, increased 

seed production, declining tree vigor, decreased leaf 

size, and loss of branches (Schomaker and others 2007). 

Inversely, an increase in crown density can be caused by: 

resurgence after insect or disease damage, recovery from 

environmental stresses, improved tree vigor, increased leaf 

size, and the addition of tree branches. Traditionally, people 

have estimated transparency by comparing the crown to 

a reference drawing or photograph. This method is very 

subjective and usually varies from one observer to another. 

UrbanCrowns, however, provides a more accurate, objective 

measurement of crown transparency. 

Crown Volume

Crown volume estimates can be used to quantify many tree 

functions including: carbon sequestration, pollution removal, 

rainfall interception, surface temperature reductions, and 

oxygen production. The most common method currently 

used to estimate crown volume from the ground involves 

first measuring crown ratio, crown diameter, tree length, 

and crown density. These variables are then plugged into 

a volume equation to obtain an estimate of crown volume. 

One problem with using this method is that it does not take 

into account the shape of the crown.

UrbanCrowns is unique in that it can provide an accurate 

estimate of crown volume using only one view of the tree. 

The program first determines the actual width and height 

represented by each row of pixels within the selection 

region. An imaginary cylinder is generated for each row 

of pixels that has a height equal to the calculated height 

of one pixel and a diameter equal to the calculated width 

of the row. The volume estimates for each row of pixels 

are summed to obtain the volume estimate for the entire 

crown selection region (fig. 13). This estimate includes tree 

structure and void areas, so the volume is then multiplied by 

the crown density to get a volume estimate that includes tree 

Figure 13—Illustration showing how UrbanCrowns determines crown volume using a single view of the tree.
10

structures only. This method of determining volume works 

well for crowns that are relatively symmetrical around the 

entire tree. For crowns that are significantly asymmetrical, 

such as trees pruned around power lines, it may be necessary 

to analyze a second photograph taken perpendicular to the 

first and calculate the average volume.

Conclusion

Trees are a vital part of urban communities. To ensure 

their health and survival in such a stressful environment, 

inventories are often conducted to identify declining 

or hazardous trees. To more efficiently and accurately 

evaluate the condition of an urban forest, tree managers 

need intuitive, practical, and cost-effective tools to assess 

individual trees and monitor their condition. Since tree 

crown characteristics serve as good indicators of overall 

tree health, the Forest Service developed the UrbanCrowns 

computer program to assist with urban tree assessment. The 

software can be used to monitor individual tree growth or 

decline over time and can also help quantify tree benefits 

such as rainfall interception, carbon sequestration, energy 

reductions, and pollution removal. 

Literature Cited

Heisler, G.M. 1986. Energy savings with trees. Journal of 

Arboriculture. 12(5): 113-125.

Nowak, D.J.; Crane, D.E.; Stevens, J.C. 2006. Air pollution 

removal by urban trees and shrubs in the United States. Urban 

Forestry and Urban Greening. 4: 115-123.

Nowak, D.J.; Wang, J.; Endreny, T. 2007. Environmental and 

economic benefits of preserving forests within urban areas: air 

and water quality. In: de Brun, C.T.F., ed. The economic benefits 

of land conservation. San Francisco, CA: The Trust for Public 

Land: 28-47.

Roberts, B.R. 1977. The response of urban trees to abiotic stress. 

Journal of Arboriculture. 3(4): 75-78.

Schomaker, M.E.; Zarnoch, S.J.; Bechtold, W.A. [and others].

2007. Crown-condition classification: a guide to data collection 

and analysis. Gen. Tech. Rep. SRS–102. Asheville, NC: U.S. 

Department of Agriculture, Forest Service, Southern Research 

Station. 78 p.

UrbanCrowns Could Aid 

i-Tree Applications

According to itreetools.org, “i-Tree is a 

state-of-the-art, peer-reviewed software 

suite from the USDA Forest Service 

that provides urban forestry analysis 

and benefits assessment tools. The 

i-Tree Tools help communities of all 

sizes to strengthen their urban forest 

management and advocacy efforts by 

quantifying the structure of community 

trees and the environmental services 

that trees provide.” Key variables used 

in the i-Tree Eco assessment tool 

(such as tree height, crown width, and 

transparency) are similar to the data 

generated by UrbanCrowns. Another 

potential use is in the i-Tree Storm tool, 

which analyzes storm damage debris 

from urban trees. UrbanCrowns could 

be used to document the condition of 

damaged tree crowns and monitor their 

recovery for years after the damaging 

event. The approaches are slightly 

different and changes to the i-Tree 

applications would be necessary in 

order to incorporate UrbanCrowns data.

The UrbanCrowns software is available for download at the following address:

http://www.srs.fs.usda.gov/pubs/software/urbancrowns.zip


Winn, Matthew F.; Araman, Philip A.; Lee, Sang-Mook. 2011. UrbanCrowns: an assessment 

and monitoring tool for urban trees. Gen. Tech. Rep. SRS-135. Asheville, NC: U.S. Department 

of Agriculture, Forest Service, Southern Research Station, 10 p.

UrbanCrowns is a Windows®-based computer program used to assess the crown characteristics of 

urban trees. The software analyzes side-view digital photographs of trees to compute several crown 

metrics, including crown height, crown diameter, live crown ratio, crown volume, crown density, 

and crown transparency. Potential uses of the UrbanCrowns program include monitoring individual 

tree growth over time, detecting disease or insect damage in early stages, and providing data to 

quantify tree benefits such as carbon sequestration, rainfall interception, energy conservation, 

pollution removal, and oxygen production.

Keywords: Crown characteristics, crown volume, monitoring, transparency, urban forestry, urban 

trees.
The Forest Service, United States Department 

of Agriculture (USDA), is dedicated to the 

principle of multiple use management of the 

Nation’s forest resources for sustained yields of wood, 

water, forage, wildlife, and recreation. Through forestry 

research, cooperation with the States and private forest 

owners, and management of the National Forests 

and National Grasslands, it strives—as directed by 

Congress—to provide increasingly greater service to a 

growing Nation.

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and activities on the basis of race, color, national 

origin, age, disability, and where applicable, sex, marital 

status, familial status, parental status, religion, sexual 

orientation, genetic information, political beliefs, 

reprisal, or because all or part of an individual’s income 

is derived from any public assistance program. (Not 

all prohibited bases apply to all programs.) Persons 

with disabilities who require alternative means for 

communication of program information (Braille, large 

print, audiotape, etc.) should contact USDA’s TARGET 

Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write to USDA, 

Director, Office of Civil Rights, 1400 Independence 

Avenue, SW, Washington, D.C. 20250-9410, or call (800) 

795-3272 (voice) or (202) 720-6382 ( TDD). USDA is an 

equal opportunity provider and employer.