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Comparative Evaluation Tao Dong Maureen Hanratty Adam Torres Lingyun Xu SI 622: Evaluation of Systems & Services Winter 2008 Project Client: Syntax2D Taubman College of Architecture & Urban Planning University of Michigan

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Page 1: Comparative Evaluation - Adam€¦ · methods that Syntax2D provides. Path analysis and point count are the only frequently used functionalities. For other analysis (spatial con-figuration

Comparative Evaluation

Tao DongMaureen Hanratty

Adam TorresLingyun Xu

SI 622: Evaluation of Systems & ServicesWinter 2008

Project Client:Syntax2D

Taubman College of Architecture & Urban Planning

University of Michigan

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| Table of contents

Table of Contents

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

Overview of Syntax2D . . . . . . . . . . . . . 1

Literature Review . . . . . . . . . . . . . . . 2

Methodology . . . . . . . . . . . . . . . . . 3

Competing Software Products . . . . . . . . . . 4

Functionality Matrix . . . . . . . . . . . . . . 5

Detailed Findings . . . . . . . . . . . . . . . 5

Integration with other software tools . . . . . . . 5

Visibility analysis . . . . . . . . . . . . . . 5

Axial line analysis . . . . . . . . . . . . . . 7

Software interface . . . . . . . . . . . . . . 7

Ease of use . . . . . . . . . . . . . . . . 12

Open Source . . . . . . . . . . . . . . . . 14

References . . . . . . . . . . . . . . . . . 15

Appendix

Grid isovist measures . . . . . . . . . . . . . 16

Axial line measures . . . . . . . . . . . . . 17

Task flow chart: Syntax2D . . . . . . . . . . . 18

Task flow chart: Depthmap . . . . . . . . . . 20

SynTax 2.0: ComparaTive evaluaTion | I

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1 |

IntroductionThis report document is a comparative evalu-ation of Syntax2D, an open source software suite for urban and architectural spatial analysis developed at the Taubman College of Architecture & Urban Planning (TCAUP) at the University of Michigan.

The analysis starts with an overview of Syntax 2D. Next, a literature survey on spatial analysis is presented to give an idea about the state of the art in this area. An overview of the method-ologies and criteria used are given in the third section of the report. The particular systems used for comparison are Depthmap, Omini-Vista, Confeego, and Spatialist. A functionality matrix is provided to visualize the difference between the systems. Detailed findings flesh out the data documented in the functionality matrix.

Overview of Syntax2DSyntax2D is an open source spatial analysis software program developed by the Taubman College of Architecture and Urban Planning at the University of Michigan. It is a suite of tools for researchers and practitioners to analyze spatial configuration of buildings and urban spaces. Syntax2D features isovist, grid, and axial analysis as well as path analysis and counting features intended to assist with field

research. Measures such as connectivity, inte-gration and mean depth can be visualized on a grid and also exported to an Excel spreadsheet as quantitative data. Source files for Syntax2D are computer-aided design (CAD) drawings in the 2000 .DXF format.

Syntax2D is an attempt by University of Michi-gan researchers to integrate a suite of spatial analysis tools that takes advantage of current systems. Unlike the current selection of space syntax analysis tools, which were too special-ized or written for now-obsolete operating systems and CAD software, Syntax2D is devel-oped as a common platform for spatial analysis research compatible with GIS. It is capable of performing most of the existing spatial analysis measures found in current software plus sev-eral unique features and forms of analysis that are not elsewhere.

Syntax2D is used by faculty and students at the University of Michigan to conduct visibility analysis for both interior buildings and urban spaces. However, as a newly introduced spatial analysis software, Syntax2D has not exerted its full potential among the University of Michigan community. According to our user interviews, most interviewees use only small part of the methods that Syntax2D provides. Path analysis and point count are the only frequently used functionalities. For other analysis (spatial con-figuration and axial analysis), the interviewees usually turn to Depthmap with which they have

Comparative Evaluation of Syntax2D

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been acquainted for a long time.

Syntax2D distinguishes itself in the way that it is an open source platform for spatial analysis. It is free to download from the University of Michigan so long as users agree to the terms of the open source license. This allows the user to install and run the program for aca-demic research as well as to view and modify the source code. Open source methodologies have been proved to be able to correct pro-gram errors, speed development, improve the quality of tools, and enhance collaboration and research transparency. With the software and source code freely available, Syntax2D is an opportunity for the space syntax community to share and build upon their work across a com-mon framework (Wineman et al, 2008)

Literature ReviewSpace syntax is a set of theories and tech-niques for analyzing spatial layouts in build-ings and urban spaces. A layout is broken down into spatial elements, or nodes, and a graph is used to analyze relationships among the spatial elements (Major, Hillier & Hanson, 1998). Quantitative measures produced by these techniques describe how well integrated and connected, and thus human navigable, the spaces are within a system. The theories and techniques of space syntax combine the work of many scholars and were first presented as a whole in The Social Logic of Space (Hillier & Hanson, 1984).

A core theory of space syntax is the importance of visibility to an individual’s understanding of and movement through space. Gibson (1979) theorized that optic flow guides a person through an environment. Inspired by Gibson’s theories Benedikt (1979) proposed a visibility

polygon, or isovist, representing a person’s field of vision at eye height. The formal defini-tion of an isovist is “the set of all points visible from a given vantage point in space.” Isovist measures include the area and perimeter of the visibility polygon. In space syntax software programs a mouse click on a point in the layout generates the visibility polygon of an individual vantage point. This is referred to as a point isovist.

Space syntax can be used to describe the visibility for an entire spatial configuration, in a process called visibility graph analysis. It is used to determine how visible any point in the spatial configuration is from any other point (Turner, 2003). Measures generated from vis-ibility graph analysis include connectivity, the “measure of how many other viewpoints are visible from a viewpoint,” and mean depth, “the average depth from one element to all others,” (Dalton & Dalton, 2001; Turner, 2003). Visibility measures from visibility graph analysis have been shown to correlate highly with observed pedestrian movement in an urban context (De-syllas & Duxbury, 2001).

Visibility analysis can also be performed on a path (path isovist) and points (point count). Re-searchers usually create drawings of paths and points from direct observational studies of in-dividuals in a building or urban context. A path represents an individual’s movement through a space. A point may represent a spot where an individual stopped. By applying visibility analysis to these paths and points, researchers seek to understand whether the spatial layout of the space effects an individual’s movement through it.

Axial line analysis is another space syntax method. Axial lines are the fewest and longest lines of site in a spatial configuration. Strate-

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gic points often occur where axial lines con-verge, thus axial analysis has been called the “workhorse of urban analysis,” (Major, Hillier & Hanson, 1998). Key measures derived from axial analysis include integration, “the degree to which each line in the map is present on the simplest (fewest changes of direction) routes to and from all other lines,” connectivity, “the number of lines that intersect with each line in the system,” and mean depth, “the number of changes of direction any line in a system is away from a selected line,” (Major, Hillier & Hanson, 1998). The reliability of axial line analysis has often been called into question because axial lines were not, until recently, algorithmically generated but drawn by hand (Desyllas & Duxbury, 2001).

Applications for space syntax are numerous. In addition to predicting pedestrian move-ment through urban space, space syntax has been used by archeologists to understand how spatial layouts of domestic spaces reflect familial and social structures (Dawson, 2002). At the University of Michigan researchers are using space syntax in a variety of ways. An interdisciplinary team of architectural design and organizational studies researchers, funded by a multi-year grant from the National Science Foundation, are combining spatial analysis and social network analysis to understand how innovation occurs in Fortune 500 companies. Healthy Environments Partnership: Lean & Green in Motown Project is a National Insti-tutes of Health funded project to investigate how spatial characteristics of metro Detroit neighborhoods affect walking and exercise and how this correlates with health measures such as obesity. In addition to the University of Michigan the two other major space syntax uni-versity research centers are the Bartlett School at the University College of London and the

Georgia Institute of Technology in Atlanta.

MethodologyResearchers performed a comparative evalua-tion between Syntax2D and some of its com-petitors through comparisons of functionality, usability, and aesthetics to gain an overview of differences that may be addressed in the next development cycle.

Syntax2D has many features, specifically when considering the types of analyses (path analy-sis or axial line analysis) it can perform. In this comparison researchers will be focusing on the user interface and analysis type features, but also which operating systems are supported and how each integrates with other software being used. In the user interface comparison, researchers will focus on how user interface elements are used, and whether it supports advanced users. In the analysis types compari-son, researchers will perform a simple analysis type inventory for each application. Feature comparison will take place in the form of a functionality matrix, which will provide a quick overview of features available in each compet-ing application, and detailed findings.

Syntax2D Program Coordinator Nick Senske provided some competitive applications to re-searchers, while others were identified through user interviews. There is a small number of applications performing space syntax analysis and one application called Depthmap, is used by the majority of researchers in the space syn-tax field. In our comparative analysis, research-ers have chosen to focus on four software applications to compare with Syntax2D: Depth-map, Confeego, Omnivista, and Spatialist.

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Competing Software ProductsDepthmap (http://www.vr.ucl.ac.uk/depthmap/handbook.html).

Depthmap is a spatial network analysis pro-gram developed by Alasdair Turner at Univer-sity College London VR Center for The Built Environment. Depthmap was written for the Silicon Graphics IRIX operating system as a simple isovist processing program in 1998. Since then it has gone through several meta-morphoses to reach the current version 7.12.00

Depthmap is designed to run on Windows 2000 and XP operating systems. It is a stand-alone program to perform a set of spatial network analysis designed to understand social processes within the built environment. The analyses available within Depthmap include the original visibility analysis, generation and analysis of axial maps as well as segment analysis. In addition, a plug-in module gives us-ers the ability to perform agent-based analysis.

Depthmap supports importing to import plan drawings (e.g. DXF files) generated by other programs (e.g. AutoCAD). For developers, it provides a “software developers kit” (SDK) that allows extending its functions. Depthmap is free for academic use. To get a license for the program, you need to register on its webpage.

OmniVista

OmniVista is an isovist generating applica-tion developed by Nick Sheep Dalton and Ruth Conroy Dalton. OmniVista is a privately written piece of software with no institutional affiliations. It was first developed in February 1999 and completed by mid-March 1999. It is a stand-alone program designed to run on Apple Macintosh platform. OmniVista is able to

perform a range of isovist measures including single isovists, grid isovists and path isovists (Dalton & Dalton, 2001).

This program is not active today.

Confeego (http://www.spacesyntax.org/soft-ware/newtools.asp)

Confeego is a suite of new tools developed by the commercial company Space Syntax Limited for use in its research and consulting projects. Confeego will run in demonstration mode for one month following installation. After that, it will not run again until you obtain and install a free researcher licence key. It runs on PCs inside the MapInfo Professional GIS (Geo-graphic Information Systems) environment, version 6.5 or higher. The version (v 1.0) that we are evaluating was released in July 2005.

The current release of Confeego facilitates three analytical tasks: calculating point depth, calculating integration and associated mea-sures, and graphically exploring relationships between spatial maps and associated statisti-cal plots with the JMP statistical package. How-ever, users have high flexibility with Confeego in exploring spatial-statistical relationships, as it allows users to select any object capable of being represented in MapInfo and finding it in any type of graph or plot capable of being generated in JMP.

Spatialist (http://web.archive.org/web/20010515074956/murmur.arch.gatech.edu/~spatial/)

Spatialist was developed by Don Harris and Mark Weisman at the Georgia Institute of Technology for the purpose of implementing theoretical innovations principally introduced by John Peponis. Spatialist is a tool for the

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their analysis. Therefore it is vital that space syntax software programs use file formats that popular CAD software programs generate. Autodesk’s CAD program AutoCAD dominates the market for CAD software. Its native file type is .DWG but it also supports .DXF and .DWF file formats (AutoCAD, 2008). AutoCAD runs exclusively on Microsoft operating systems. Though it is technically possible to run Auto-CAD on PC virtualization software performance issues make this highly undesirable.

The demise of OmniVista and Spatialist can probably be attributed to their failure to inte-grate with AutoCAD. OmniVista was written for the Macintosh operating system. University architecture programs and commercial archi-tectural practices do not use Macintosh com-puters because it does not support AutoCAD. Spatialist ran exclusively on Bentley Inc.’s Microstation 95 CAD software. Microstation 95 still exists but has very little market share.

For the foreseeable future, space syntax software programs must be suited to software platforms that run on, and file formats that are supported by, AutoCAD.

Though both Syntax2D and Depthmap use the AutoCAD .DXF file format, Syntax2D requires AutoCAD 2000 version of the .DXF file. Depth-map does not specify a version of .DXF and it is assumed that Depthmap supports current .DXF file formats. Users interviewed reported that they would prefer Syntax2D supported the most current version of .DXF.

Visibility analysis: Grid Isovists, Path Analy-sis and Point CountThe “Measures” section of the functionality ma-trix lists the number of measures each software product generates for certain types of analy-ses. A full breakdown of the types of measures

study and analysis of the plans of buildings or settlements. “Spatialist” is written as a plug-in application for Microstation 95, a CAD pack-age from Bentley Inc. and is available for both Macintosh and Windows platforms.

The latest version performs four types of analyses on plans of buildings or settlements: e-partition, s-partition, visual field and lines. The input for the first three is the same: a plan layout simplified by representing all the walls as straight-line segments without thickness. Of the three, the e- and s-partition analyses in-volve partitioning the plan into discrete convex spaces according to the information about its shape available to an observer situated “inside” the plan, and using graph-theoretical methods to study the resulting configuration of convex spaces. The third, visual field analysis, involves computing the visibility polygons from a set of specified points inside the plan and studying their properties.

Spatialist may be used to study: 1) how spatial systems become intelligible and how are they explored; 2) what patterns of co-awareness and co-presence are sustained by virtue of spatial structure; 3) how does spatial layout influence informal communication and the exposure to information?

This program is not active today.

Functionality Matrix(see following page)

Detailed FindingsIntegration with other software tools All space syntax software programs require a computer aided design (CAD) file to perform

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the products provide (connectivity, integration, etc.) can be found in the appendix. Syntax2D and its main competitor Depthmap generate approximately the same number of measures for grid isovist, 27 and 30 respectively.

Path analysis is a method that is supported by Syntax2D and Omnivista. Whereas Omnivista generated two measures from path analysis, Syntax2D provides twelve different measures. Depthmap does not support path analysis. A user can import paths and view them on the canvas but Depthmap does not allow the user to take any isovist measures from the path. Researchers discovered through user inter-views that path analysis was the prime moti-vating factor for using Syntax2D. Interviewees reported that they usually use Depthmap, a program that users are more familiar with, to run the other visibility analysis and only ac-cess Syntax2D when they wanted to run a path analysis. It is reasonable to assume that users would not use Syntax2D if Depthmap provided path analysis. In addition Syntax2D is the only software program that supports point count.

In interviews users reported that the grid isovist generated by Depthmap was more fine-grained than the grid generated by Syntax2D. Indeed the default grid created by Depthmap produced a larger number of cells than the default grid generated in Syntax2D. Researchers could not, however, determine the maximum cell count produced for either program. It was, therefore, impossible for the research team to definitively conclude whether Depthmap is capable of generating more fine-grained graphs, and thus more accurate quantitative measures, than Syntax2D.

Axial line analysisAxial line is the ‘longest line of sight and ac-cess’ through open space. Both Syntax2D and

Depthmap provide axial line analysis method. However, in addition to axial line analysis, Depthmap is also able to generate axial lines automatically. This means users do not have to get ready axial lines in CAD program before-hand as they do with Syntax2D. In Depthmap, at the small to medium urban scale, the pro-gram can derive an ‘axial map’ of a layout. That is, derive a reduced straight-line network of the open space in an environment. Once the map has been generated, it may be analyzed using graph measures. For larger systems where the derivation algorithm becomes cumbersome, pre-drawn axial maps may be imported. The program will make axial map from drawing lay-ers and later run analysis on it.

Depthmap’s ability to generate axial lines was intended to settle the debate on whether or not there is a simple (and `correct’) algorithm underlying the process by which axial maps have traditionally been drawn by hand (Turner, A., 2007)

In our user interviews, some interviewees expressed their preference to use Depthmap to do axial line analysis because of the conve-nience of axial line auto-generating.

InterfaceWe compared the user interfaces for Syntax2D and Depthmap on a number of aspects found within our interviews. The areas of comparison are: switching between measures, toolbars, and multiple document implementations.

Switching Between MeasuresOnce an analysis has been created, the user can switch between many different mea-sures to be displayed and knowing which are available quickly is useful. Each program has significantly different implementations of presenting the user with measures applicable

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Figure 1. Image of Syntax2D after Grid Isovist was created. Notice there are no alternative measures visibly available.

Figure 2. Notice the number of measures a user can select, as well as, the number of levels these measures are found in the menuing system.

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to their analysis. In Syntax2D, the user runs the analysis and the display shows a default measures, usually area (this is not the case with an axial analysis), but other measures that can be viewed are not visible as shown in figure 1. In order for a user to display an alter-nate measure, they must select the measure in the ‘Show Grid Properties’ menu found in the Grid menu pull down as shown in figure 2. The menu to select a different measure is two levels into the menuing system, which requires more effort from the user.

The implementation used by Depthmap utilizes a sidebar that displays measures that are ap-plicable to the analysis created. For instance, if the user created the same visibly grid as seen in the figures 1 and 2 of Syntax2D, the sidebar populates with measures fitting the context of the analysis as seen in figure 3. The user sim-ply clicks on the measure they wish to view and

the display changes accordingly. This provides the user with a much easier method of display-ing different measures. It makes all possible measures that can be viewed at anytime more visible, and only provides measures that are applicable to the analysis. In contrast, Syn-tax2D provides all the measures all the time, applicable or not. It provides measures that cannot be calculated from the analysis that has been conducted, leading the user to believe that certain measures are available when they are not.

The sidebar implementation used in Depthmap filters the measures that are applicable to the analysis for the user, whereas Syntax2D does not. Depthmap also makes it easier for the user to recognize measures, rather than recall them as they do in Syntax2D.

Figure 3. Sidebar is populated with all possible measure that can viewed after the analysis has completed.

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ToolbarsSyntax2D has 32 tools on the toolbar com-pared to Depthmap that has 21 toolbars showing, but 26 total as shown in figure 4. The Syntax2D toolbar allows users to do a com-plete analysis right from the toolbar. The user can import or open a document from the tool-bar, set the grid, initialize the grid, and create the grid isovist. During our interviews, having a robust toolbar was mentioned as a desirable feature. It also supports users who are more familiar with the program and allows those them to proceed at a much faster pace when attempting to complete tasks. Depthmap’s toolbar does not allow users to complete an analysis by using only the toolbar. In addition, the lack of this feature does not allow for more expert users to capitalize on their familiarity and complete task in a more efficient manner. It forces all users to continue relying on the menu bar drop downs. With Depthmap’s toolbar a user can import a DXF file, set the grid, and initialize the grid, but a user cannot perform the analysis with a single click.

In terms of aesthetics, both toolbars utilize hard to read icons that seem cryptic and difficult to understand. Perhaps the use of larger, more detailed icons would be useful.

Document InterfaceEach program implements multiple documents handling differently. In Syntax2D, multiple documents are actually multiple instances of the program, as shown in figure 5. Syntax2D

utilizes a single-document interface (SDI) where each window is another instance of the program. In contrast, Depthmap has imple-mented a multiple-document interface (MDI), meaning each file imported is contained within Depthmap’s program window, shown in figure 6. By using a MDI, Depthmap is utilizing a sin-gle toolbar to control each document within its container. Syntax2D must replicate the toolbar for each window; therefore the user must refer to two toolbars in two different locations, which can cause confusion and waste time. One benefit to using the SDI is that users can toggle between Syntax2D windows quickly because each instance of the Syntax2D is displayed in the task bar within Windows, which is not the case with Depthmap. It should be noted that users can have multiple instances of Depthmap running concurrently.

ZoomingIt was noted in interviews that zooming is a critical task when using both programs. Both programs support zooming using the scroll wheel on a mouse, but the implementation of zooming is different. In Syntax2D, when a user zooms, the center of the window is the point that increases in size. The point of interest on the image needs to be the center of the screen in order to zoom in on it. In Depthmap, the point of zoom is where the mouse is currently positioned. This might sound beneficial, but it makes zooming very difficult because it re-quires the user to reposition the mouse after each level of zoom or each click on the scroll

Figure 4. Top: Syntax2D Toolbar. Bottom: Depthmap Toolbar.

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Figure 5. Single-Document Interface of Syntax2D.

Figure 6. Multiple-Document Interface of Depthmap.

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wheel. Therefore, zooming takes much more effort in Depthmap than in Syntax2D.

Depthmap does have a zooming feature that is implemented very well, which is the selection zoom. A user can select the magnifying glass icon, click and drag to select the area in which they would like to zoom in on, let go after the selection is made, and the result is a perfectly zoomed image. At the moment, Syntax2D does not offer this kind of feature, but could benefit from a precision zooming tool.

Ease of UseIntroductionWe will compare the ease of use between Syntax2D and Depthmap by walking though a sample task on each program. The task is to create a visibility diagram for grid isovist analy-sis. We will first describe the task and then visualize the process of performing this task in Syntax2D and Depthmap with flow charts. Finally, we will identify and discuss four key differences between Syntax2D and Depthmap that contributing users’ perceived ease of use.

Task DescriptionThe following is a description for the sample task:

The user’s goal is to run a grid isovist analysis for a floor plan and record measures in some points of the plan. The user has a .DXF file of a floor plan created by AutoCAD.

Flow Charts for the Sample Task (see Appen-dix)Basic Characteristics of InteractionThe following table depicts the basic quantita-tive characteristics of the interaction between a user and each program. The total number of clicks and the total number of user-program

dialogs are very close for the two programs. However, the distribution of mouse clicking and dialogs reveal some key differences between Syntax2D and Depthmap.

Clicks User-Program Dialogs

Syntax 2D 13-17 4

DepthMap 14 3

Key Differences1. Importing Layers

We found Depthmap does a far better job than Syntax2D on importing layers from DXF files. In Syntax2D, users have to specify a name for each layer, if the actual layer name is different from the default value preset by the program (see step S-7 and S-7). This requires users to memorize the layer names of the importing file and cause a cognitive burden for users. Depthmap, by contrast, is able to automatically detect layer names and import all the layers in a DFX file once. This approach helps users focus on their goal without undesirable interfer-ence.

2. Range Selection

Range Selection is a unique function offered in Depthmap. It allows users to use “fill” or “pencil” tools to select a certain range to gener-ate a visibility graph (e.g. step D-15). However, there is no cue directing users to select a range before generating a visibility graph. If no range is selected, nothing will happen after the user clicks the menu item “Tools -> Visibility -> Make Visibility Graph.”

In Syntax2D, users cannot select a particular range on the plan. An all-plan visibility graph will be generated.

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3. Visibility Graph Generation Process

It is quite handy to perform all the steps for generating a visibility graph by clicking toolbar buttons in Syntax2D. However, there are three unnecessary clicks in the process of complet-ing the sample task. In the flow chart of Syn-tax2D, the clicks in step S-18, S-22, and S-24 are redundant. Those operations can be either automated or integrated to the adjacent opera-tions.

The overall process of creating a visibility graph in Depthmap is quite smooth except two steps. The first shortcoming is that there are no clues that direct users to “fill” a range before making a visibility graph, nor does an error message pop up when you click “make visibility graph” without selecting a range on the graph. The second shortcoming is that you can do ev-ery operation on the toolbar except the “make visibility graph” operation. You have to use the menu item to complete this operation. It breaks the smooth experience of performing the task.

4. Presentation of the measure

Users have complained about the presentation

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of the measure in Syntax2D during interview. We found that there are no numeric measures of the coordinate, the total number of grids or the dimensions of the graph being displayed in Syntax2D. Depthmap, in contrast, displays the total number of grids, the dimensions of the graph, the coordinate of the location that the cursor is currently pointing to on the status bar. And the isovist value of a grid shows up when the cursor is hovering above the grid.

Syntax2D offers three ways to help the user track the isovist value of a grid. First, there is a color-value key on the left side of the canvas. Users can look up isovist value based on color. However, it is very hard to distinguish values within a small color range, for example to dis-tinguish the shades of orange from each other. The isovist value also shows up near a point when the point is clicked, but the font is too small to be legible. The third way to look up the measure of a point is to check out the “Isovist Properties” dialog box by click the menu item “Isovist -> Point Isovist Properties.”

Open Code Base

Figure 7. In Depthmap a mouseover displays isovist value. Coordinates for the point appear of the status bar.

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tions. Furthermore, the program provides a ‘DLL’ interface to allow users who program with Visual Basic, C++ or Java to create compatible plugin applications for Depthmap. By adding such plugins, more sophisticated users as well as developers are able to add much more mea-sures without having to create an entire new version of Depthmap.

Syntax2D is free to download from the Univer-sity of Michigan so long as users agree to the terms of the open source license. No registra-tion is required. Users may install and run the program for academic research as well as to view and modify the source code. Users are under no obligation to share any modifications they make, but cannot re-release programs containing Syntax2D code in the form of com-mercial software. Papers published using software derived from any Syntax2D code must cite the authors of the original code.

Depthmap can also be downloaded for free but people have to register and provide details of their academic affiliation. Depthmap allows us-ers to write their own formulae using SalaScript to replace attributes calculated by Depthmap, and to select graph objects according to condi-

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Figure 8. Point isovist analysis in Syntax2D.

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Turner, A. (2001). Depthmap 4: A Researcher’s handbook.

Wineman, J., Turner, J., Psarra, S., Jung, S. K., & Senske, N. (2008). Syntax2D: An open-source software platform for space syntax analysis

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Dalton, R. C., & Dalton, N. OmniVista: An application for isovist field and path analysis. Paper presented at theThird International Space Syntax Symposium, Georgia Institute of Technology.

Desyllas, J., & Duxbury, E. (2001). Axial maps and visibility graph analysis: A comparison of their methodology and use in models of urban pedestrian movement. Paper presented at the Third International Space Syntax Symposium, Georgia Institute of Technology.

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