‘Sensor’ship and Spatial Data Quality

Abstract

This article describes a Los Angeles-based website that collects volunteered geographic information (VGI) on outdoor advertising using the Google Street View interface. The Billboard Map website was designed to help the city regulate signage. The Los Angeles landscape is thick with advertising, and the city efforts to count total of signs has been stymied by litigation and political pressure. Because outdoor advertising is designed to be seen, the community collectively knows how many and where signs exist. As such, outdoor advertising is a perfect subject for VGI. This paper analyzes the Los Angeles community's entries in the Billboard Map website both quantitatively and qualitatively. I find that members of the public are well able to map outdoor advertisements, successfully employing the Google Street View interface to pinpoint sign locations. However, the community proved unaware of the regulatory distinctions between types of signs, mapping many more signs than those the city technically designates as billboards. Though these findings might suggest spatial data quality issues in the use of VGI for municipal record-keeping, I argue that the Billboard Map teaches an important lesson about how the public's conceptualization of the urban landscape differs from that envisioned by city planners. In particular, I argue that community members see the landscape of advertising holistically, while city agents treat the landscape as a collection of individual categories. This is important because, while Los Angeles recently banned new off-site signs, it continues to approve similar signs under new planning categories, with more in the works.

Full text

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 75
Urban Planning (ISSN: 2183-7635)
2016, Volume 1, Issue 2, Pages 75-87
Doi: 10.17645/up.v1i2.608
Article
‘Sensor’ship and Spatial Data Quality
Elisabeth Sedano
Spatial Sciences Institute, University of Southern California, CA 90089, Los Angeles, USA; E-Mail: sedano@usc.edu
Submitted: 4 March 2016 | Accepted: 16 June 2016 | Published: 24 June 2016
Abstract
This article describes a Los Angeles-based website that collects volunteered geographic information (VGI) on outdoor
advertising using the Google Street View interface. The Billboard Map website was designed to help the city regulate
signage. The Los Angeles landscape is thick with advertising, and the city efforts to count total of signs has been sty-
mied by litigation and political pressure. Because outdoor advertising is designed to be seen, the community collective-
ly knows how many and where signs exist. As such, outdoor advertising is a perfect subject for VGI. This paper analyzes
the Los Angeles community's entries in the Billboard Map website both quantitatively and qualitatively. I find that mem-
bers of the public are well able to map outdoor advertisements, successfully employing the Google Street View interface
to pinpoint sign locations. However, the community proved unaware of the regulatory distinctions between types of signs,
mapping many more signs than those the city technically designates as billboards. Though these findings might suggest
spatial data quality issues in the use of VGI for municipal record-keeping, I argue that the Billboard Map teaches an im-
portant lesson about how the public's conceptualization of the urban landscape differs from that envisioned by city plan-
ners. In particular, I argue that community members see the landscape of advertising holistically, while city agents treat
the landscape as a collection of individual categories. This is important because, while Los Angeles recently banned new
off-site signs, it continues to approve similar signs under new planning categories, with more in the works.
Keywords
categorization; landscape; outdoor advertising; spatial data quality; VGI
Issue
This article is part of the issue “Volunteered Geographic Information and the City”, edited by Andrew Hudson-Smith
(University College London, UK), Choon-Piew Pow (National University of Singapore, Singapore), Jin-Kyu Jung (University of
Washington, USA) and Wen Lin (Newcastle University, UK).
© 2016 by the author; licensee Cogitatio (Lisbon, Portugal). This article is licensed under a Creative Commons Attribu-
tion 4.0 International License (CC BY).
1. Introduction: Outdoor Advertising and the Los
Angeles Landscape
To outdoor advertisers, Los Angeles is “the largest out-
door advertising market in the United States”
(JCDecaux, 2007). To community activists, the city is
“ground zero of billboard blight” (M. Ashburn, personal
communication, 2011). Los Angeles has a landscape of
suburban sprawl designed for automobile travel, and it
is the home of the entertainment industry—factors
that led to a density of billboards greater than other
cities (Gudis, 2004). In the 1920s, the city began requir-
ing permits for off-site signs, signs that advertise a
product or service not available on the same site and
commonly called “billboards” (1 L.A.M.C. 4.4 §
14.4.4(B)(11)). Yet the city enacted nearly no regula-
tions as to the location and amount of billboards that
could be erected. Years later, the Department of City
Planning (2009) opined that the city’s lax regulations:
“have shaped the way signage has been incorporated
into our streetscapes, in a way that can now in retro-
spect be described as excessive. A proliferation of sign-
age adds significantly to the visual clutter for which Los
Angeles has become well-known, and points to the
need for stricter sign regulations.”
In 2002, the City of Los Angeles made two im-
portant steps toward regulating signage. It banned new
off-site signs, and it created the Off-Site Sign Periodic
Inspection Program, which charged the Department of
Building and Safety (LADBS) with creating a compre-

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 76
hensive inventory of existing off-site signs. Almost im-
mediately, outdoor advertising companies challenged
these laws in court. The three corporations that own
the lion’s share of billboards in the city held up the in-
ventory program for years, and even after the city was
legally cleared to restart the program, political pres-
sures kept the city from commencing work and, later,
releasing its results (Sedano, 2016). This article de-
scribes a project to employ volunteered geographic in-
formation (VGI) to map off-site signs in Los Angeles.
The project was begun during the years that the city’s
inventory program was stymied and was designed to
aid regulation by gathering data that the city was legal-
ly and politically unable to. Off-site signs are a perfect
subject for VGI in urban settings because signs are
made to be seen by the public at large, and there are a
lot of them. While governing bodies may not have spe-
cific knowledge of the changing landscape of signs, col-
lectively, residents do.
This article studies how urban residents mapped
the landscape of off-site signs in Los Angeles and, as
such, is positioned within the emerging field of VGI and
its concern with the quality of spatial data created by
non-professionals. Yet the article arrives at its key find-
ing—that residents understand signage far differently
than the professionals who make and enforce the zon-
ing code—by way of landscape theory. Landscape is
the field of social life, the land that we develop or
choose not to develop, and the structures we build,
mold, and maneuver around. The urban landscape is a
“palimpsest”, a concatenation of the old and the new
rather than layer upon layer (Schein, 1997, p. 662). The
guiding principle of modern landscape theory is that
landscape is both a material and a cultural construct
(Olwig, 1996). The landscape is primarily a visual field,
but not an objective one (Cosgrove, 2003). Following
art historian Berger (1972), who identifies the power
inherent in the gaze and employs the phrase “ways of
seeing” to capture the idea that perception is a learned
skill, Cosgrove (1984) posits that the landscape is seen
differently by different viewers. He studies the role of
18th and19th C. British landscape painting in remaking
both the cultural conception of landscape and the ma-
terial landscape to match this ideal of aristocratic
property owners. The relationship between the material
and the cultural is thus dialectical, and the movements
of this dialectic as they play out on the landscape are
deeply political (Mitchell, 2003). In urban settings, schol-
ars note the often wide disparity between the landscape
conceived by planning and that of lived reality (Mustafa,
2005; Scott, 1998). Expert ontologies of particular land-
scapes are a key site of contestation; the power to cre-
ate the categories by which landscape is defined and
regulated underwrites the making and remaking of the
material landscape (Robbins, 2001).
In the following section I discuss recent examples of
VGI in urban settings, highlighting municipal govern-
ments’ tendency to engage residents as sensors for
simple data and issues in spatial data quality that arise
with VGI. Next, I describe the design of the Billboard
Map website, how volunteers used the site, and the re-
sults of a field audit of the first 326 entries on the site. I
analyze these results using traditional spatial data qual-
ity factors, and I find that the data was spatially accu-
rate but that over-completeness of the dataset was an
issue as users entered more types of signs than the city
inventory enumerates. I then turn to the landscape of
Los Angeles to consider why residents might have
mapped more signs than city agents, and I find that the
landscape is suffused with off-site signs that the city
permits under a variety of new categories beyond the
categories of traditional billboards. I argue that city
agents see the landscape as a composite of individual
items, distinctly categorized. Residents, however, see
the landscape as a unified, cohesive whole. I argue that
the VGI map of signage pursuant to this vision of the
landscape shows fidelity to the landscape and to the
law, and I suggest that the limited inventory created by
the city is a tactic to obscure the true number of off-
site signs in the city.
2. Literature Review: VGI in Municipal Settings and
Spatial Data Quality
Together, the Internet, global positioning systems, mo-
bile devices equipped with spatial locators, and apps
for capturing and sharing spatial data now let persons
untrained in GIS or cartography easily create and share
spatial data and maps (Haklay, Singleton, & Parker
2008). The public has responded enthusiastically, and
the result is vast amounts of VGI—locationally refer-
enced data created by non-professionals. Much of the
data is spawned as the unplanned, individual moments
of sharing that are ubiquitous to Facebook and Insta-
gram, but some data is borne of civic and community-
minded projects, such as Cyclopath, a website for the
biking community of Minneapolis, MN, USA, to share
routes and road conditions (Priedhorsky, Jordan, &
Terveen, 2007). Viewing urban residents as “citizen
sensors” (Goodchild, 2009), local governments are in-
terested in VGI as a fount of community data. Years of
neoliberalization have left local bodies with decreased
funding for service provision, making VGI an attractive
option as residents become potential sources of free
labor (Johnson & Sieber, 2013). Ganapati (2011) identi-
fies this type of citizen engagement in three areas:
transportation information sharing, service manage-
ment, and community mapping. This speaks to a
broader use of social media by governments for data
sharing with citizens. Linders (2012) offers a typology
for citizen participation using social media by: “Citizen
Sourcing (Citizen to Government)”, “Government as a
Platform (Government to Citizen)” and “Do it Yourself
Government (Citizen to Citizen)”. Though the examples

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 77
and types are not strictly VGI, many rely on spatial data
sharing, such as Chicago’s Snow Portal for sharing and
accessing road conditions.
A key impediment to government use of VGI is mis-
trust of non-expert data (Johnson & Sieber, 2013). This
topic encompasses both the traditional issues of spatial
data quality as well as the more ontological questions
of whether the quality of VGI should be judged differ-
ently than professionally created geographic infor-
mation. In the last few decades, the judgment of
spatial data quality advanced along with the methods
of data creation (Devillers et al., 2010). Traditionally,
spatial data quality was considered solely by positional
accuracy, how closely the placement of a data point on
a map matches its actual location on the face of the
Earth (Van Oort, 2005). Spatial data quality assess-
ments now judge attribute accuracy, the validity of all
information associated with a data point besides its
position, such as the name of a river; temporal quality,
the data quality over time, with an assessment of the
rate of change of the source material and the rate at
which the dataset is updated; and completeness, the
exhaustiveness of a dataset, considering both whether
data is missing and excess data is included (Van Oort,
2005). Spatial data may now be easy to create, but
these many factors of quality are not easy to assure,
especially in formal institutional settings (Johnson &
Sieber, 2013). Metadata is also an issue: the quality of
professionally created datasets is well tested and doc-
umented, while the quality of VGI is generally not
(Mooney, Corcoran, & Winstanley, 2010). Further, VGI
often involves the mashing up of varying data types
from varying sources, undermining quality and making
it more complicated to judge (Hall, Chipeniuk, Feick,
Leahy, & Deparday, 2010). Due to these reasons for
mistrust, the reliability of VGI is a major concern
(Delavar & Devillers, 2010).
The largest and most comprehensive dataset of VGI
is OpenStreetMap (OSM); correspondingly, it is also the
most studied (Koukoletsos, Haklay, & Ellul, 2012). The
spatial data quality factors of positional accuracy, at-
tribute accuracy, and completeness OSM data of Eng-
land (Haklay, 2010), France (Girres & Touya, 2010), and
Germany (Zielstra & Zipf, 2010) have been analyzed. In
each case, researchers found positional accuracy was
very good, attribute data was incomplete, and the
completeness of the data varied widely, with nearly
complete datasets in urban areas but broad swaths of
unmapped areas outside cities. Girres and Touya
(2010) and Haklay (2010) suggest that OSM should is-
sue more stringent specifications in place of its current
informal rules for data collection and tagging, which
they note are often more suggestions for data collec-
tion and tagging than rules. However, they caution that
OSM should still allow for contributor freedom, in or-
der to maintain its volunteer base. Similarly, Van Exel,
Dias and Fruijtier (2010) argue that even for a seeming-
ly traditional type of dataset, such as OSM, traditional
spatial data quality indicators may need to be retooled.
For example, semantic accuracy may be hard to judge:
predefined schema for attribute data is uncommon in
crowdsourced datasets to allow volunteers’ “creative
input” but has a negative effect on spatial data quality.
These scholars argue that the use of the dataset be
considered before judging the quality of VGI. For in-
stance, creative and personal data should not be
judged by the same rigorous accuracy standards as a
traditional spatial dataset such as OSM.
Johnson and Sieber (2013) also find that local gov-
ernments use VGI as a participation platform to dia-
logue with residents rather than simply gain or share
information. In this vein, the field of VGI aligns with
public participation GIS (PPGIS) and its concern with
democratizing the tool of GIS. PPGIS is a broad field, in-
corporating a wide variety of peoples, contexts, and
methods to achieve the goal of community empower-
ment (Elwood, 2008; Sieber, 2006). “At its heart, the
overlap between PPGIS and VGI relies on the investiga-
tion by individuals of locations that are important to
them” (Tulloch, 2008, p. 164). The fields diverge, he ar-
gues, in that, “VGI is more about applications and in-
formation while PPGIS seems more concerned
processes and outcome” (Tulloch, 2008, p. 170). The
critical work of PPGIS is directly relevant to the analysis
of VGI and in many ways is the necessary precursor and
backdrop to its analysis (Elwood, 2008). Key in PPGIS is
to “conceptualize data as socially produced and em-
bedded” (Elwood, 2008, p. 177) and acknowledge the
“difficulty of integrating spatial data that originate
from different epistemologies, as ‘local knowledge’ and
‘official knowledge’ often do” (Elwood, 2008, p. 180).
Still, implementations of VGI systems by planning and
other government agencies to engage with the public
in what might be deemed participation rather than
simply information sharing are “sparse” (Rinner, Kuma-
ri, & Mavedati, 2011), if not “few and far between”
(Ganapati, 2011). In the vast majority of VGI literature,
urban residents are understood as “sensors”, whose
unique experience of the urban landscape is only rec-
ognized for making them “expert sensors” of the land-
scape than as potential partners in planning
deliberation (see, e.g., Karimipour & Azari, 2015). Gov-
ernments’ failure to use VGI for community participa-
tion reflects the failure of official planners and
decision-makers to sustain community participation
generally. Brown (2012) argues that improvement in
PPGIS technologies and techniques have not resulted in
meaningful participation, because government agen-
cies do not accept it. In an evaluation of ten years of
PPGIS projects, Brown “has yet to observe any tangible
evidence that PPGIS data has been used in agency de-
cision making, let alone influence and improve the sub-
stantive quality of decisions in planning outcomes”
(Brown, 2012, p. 14).

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 78
3. The Billboard Map Website: Description
Weeks after the billboard inventory ordinance was
passed in 2002, the largest outdoor advertising com-
panies in the area brought actions in state and federal
court to halt the program. The cases settled in early
2007, but the city did not restart the program. When
asked by the media why the program was stalled,
LADBS personnel stated that litigation prevented the
program from being restarted; however, the City At-
torney’s office admitted that no current litigation was
preventing the program (Pelisek, 2008). The Billboard
Map website was envisioned to fill this data vacuum.
The goal was to create a map that might match the in-
ventory of off-site signs that that the city had planned
but, at that time, had neither completed nor released
due to political and legal pressure. The design impera-
tive was to collect data that the city could use in its
regulatory effort.
Google is a common basis for VGI projects due to
the ubiquity of Google Maps and the availability the
Google Maps API. Similar to this project’s goal, John-
son, Belblidia and Campbell (2011) create a publicly ac-
cessible urban dataset using Google mapping tools.
They employ Google Earth’s satellite imagery to map
vacant lots in Detroit. This project employed the
Google Maps API for the site’s base map and the
Google Street View (GSV) interface rather than satellite
imagery to locate signs. Billboards have a relatively
small footprint compared to their sign faces, and they
are difficult to identify from above, making satellite
imagery ineffective for locating signs. GSV is a feature
of Google Maps that shows street-level photographic
imagery of streetscapes within the context of a map
(Anguelov et al., 2010). The GSV interface provides full
pan, tilt, and zoom capabilities from a user’s perspec-
tive. A user can rotate the current view to turn the
view a complete 360 degrees, zoom the camera in and
out at a particular location in front of the camera, and
increase or decrease the pitch of the view to move the
field of view up or down and towards or away from the
horizon. The user can proceed down a street by clicking
to the next available camera position or by clicking on a
location in the distance. Google updates its GSV da-
taset at specific locations approximately every eighteen
months (Badland, Opit, Witten, Kearns, & Mavoa,
2010).
Since its inception, scientists have tested GSV for
usability and relied on its growing dataset as a basis of
research. On point for this project are studies that use
GSV as source for streetscape audits. Badland et al.
(2010) find GSV audits to be faster and less expensive
than physical site visits and that efficiency improves
rapidly with user experience. Curtis, Duval-Diop and
Novak (2010) use GSV to audit New Orleans to identify
neighborhood patterns of return and rebuilding after
Hurricane Katrina. Although video was available from
local community groups, the authors find that GSV is
just as effective and chose to rely on GSV as their data
source so that their methods could easily be replicated.
The design of this project was inspired their work. The
design of the Billboard Map pushed beyond the exist-
ing literature on GSV streetscape audits by relying on
non-experts.
As with other community-minded VGI websites, the
desire for broad-based participation was countered by
the desire for accurate data. I followed the lead of the
Cyclopath designers (Priedhorsky et al., 2007) by favor-
ing open access over site control that might enhance
spatial data quality. The site thus operated as a Wiki:
users were responsible for creating the data and main-
taining the quality of the entries through edits and de-
letions of errors. Steps to promote more accurate data
collection, such as in-person training, online training,
and mandatory online instructions will invariably dis-
courage some potential users from participating. I opt-
ed to make instructions available on the site but not to
require them for participation. Requiring users to regis-
ter with the site prior to usage was also seen as a way
to increase data quality, on the assumption that if one
cares enough to register with the site then one will
tend to be more careful in entering data than an anon-
ymous visitor. Differing from Cyclopath here, I opted for
open access and chose to allow users to add map points
without registering. However, registration was required
to edit and delete existing billboard entries.
The home page featured a map frame that opened
on the extent of all current sign entries, above a table
listing the entries (Figure 1). The user could scroll and
zoom with the standard Google Maps controls. To the
left of the map was a bar with instructions on using the
system, which a user could click to hide for a larger
map view.
To begin the process of recording signs, the user
clicked on a location in the main mapping interface.
This action launched a pop-up window with three main
features: (1) a window with the GSV viewshed directed
northwards from the point selected by the user; (2) a
map window centered on the point; and (3) attribute
information fields including the approximate address of
the point, estimated using employed using the lati-
tude/longitude supplied by the Google Maps API and a
reverse geocoding process described by Goldberg and
Cockburn (2010) (Figure 2). In the viewshed window, a
red rectangular box overlain on the image was used to
identify the location of a sign in 3D space. Users
panned and zoomed the GSV image until the red rec-
tangle surrounded the sign of interest. When the user
saved the entry, the program computed the 3D spatial
location of the billboard, and the map updated in real-
time to show the new entry.

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 79
Figure 1. The home page of the Billboard Map website, featuring a Google Maps base map and points of signs entered
by users.
Figure 2. The Billboard Map's pop-up window for data collection, featuring a Google Street View window, a map win-
dow, and fields for attribute data.

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 80
The pop-up window also provided fields for users to
record the sign attributes that were collected by city
inspectors during their fieldwork. These attributes,
identified by the head of the city’s inspection program,
included: (1) number of sign faces (many signs are
double-faced, with sign faces on the front and back);
(2) lighted or unlighted; (3) digital or non-digital; and
(4) type of sign: pole, wall, roof (L. Zamperini, personal
communication, April 13, 2010) (Figure 3). Finally, the
window provided a “Notes” space for users to provide
free-form comments on the sign.
I reached potential users by notifying online media
venues of the project, and a variety of these venues
publicized the site. The Coalition to Ban Billboard Blight
(CBBB) described the project in a blog post. Their sub-
scriber list is relatively small compared to the other
venues, but the audience is directly interested in the
topic. Curbed LA, a website covering local real estate
development, and the website of the Los Angeles
Times, the main regional newspaper, both covered the
project. According to Google Analytics, the majority of
visitors to the Billboard Map who entered at least one
sign on the map linked to the page from either CBBB or
Curbed LA. This finding was not surprising as the pro-
ject relied solely on user interest in the topic to gener-
ate engagement: unlike VGI studies that offer gifts
(Brown & Kyttä, 2016), the Billboard Map offered users
no monetary or material reward. From February
through April, 2011, 31 users registered with the site,
and many used the site without registering. In this time
period, 326 entries were added to the map. 326 entries
provided a sizeable enough collection to test the usa-
bility of the initial incarnation of the site for its intend-
ed purpose—supplementing the official inventory of
signs. In the following section, I describe the spatial da-
ta quality of these entries.
Figure 3. Examples of types of signs and sign attributes collected by the city inventory and the Billboard Map, including
(a) a double-sided pole sign; (b) a lighted roof sign; and (c) two digital pole signs.

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 81
4. The Billboard Map Website: Results and Analysis of
Spatial Data Quality
The Billboard Map, like most existing VGI systems cur-
rently employed in municipal governance (Ganapati,
2011), envisioned the residents of Los Angeles as sen-
sors rather than as partners or participants in planning
or policy deliberations. The site was intended to collect
data useful for regulation, specifically to help the
LADBS catalog signs. City agents charged with the day-
to-day tasks of regulation, for example with maintain-
ing permits and enforcing municipal codes, require ac-
curate data for their work. To consider the utility of the
Billboard Map for this purpose, testing the traditional
spatial data quality parameters of the VGI data against
the expectations of the city inspectors is key.
The spatial data quality of the 326 volunteered en-
tries in the Billboard Map was based on ground-
truthing of the data rather than a comparison against a
reference data set as used in other tests of VGI accura-
cy (see, e.g. Haklay, 2010). Because the city had not yet
released its inventory in 2011, and no other public da-
taset of existing signs existed, there was no reference
data set against which to compare the VGI entries. A
field test of the 326 entries was therefore required,
and it was completed using a Trimble GeoXH GPS re-
ceiver to record location and attribute data. After the
city’s inventory was released in late 2012, I was able to
confirm my findings against the city’s dataset (Los An-
geles Department of Building and Safety, 2014).
The first result sought was the positional accuracy
of the web entries. Using ArcMap, I calculated the dis-
tance between the location of web entries with the lo-
cation of corresponding field entries using the “XY to
Line” tool, chosen because it yields the desired dis-
tance calculation, as well as a visual confirmation of
the process (Figure 4). Prior to running the process, I
corrected the location of the field points using 4” pixel
resolution natural color orthophotography from the
2012 Los Angeles Regional Imagery Acquisition Consor-
tium dataset. This test showed that 43% of web entries
were within 20 feet of the intended sign, 75% were lo-
cated within 50 feet and 91% were located with 100
feet. The city’s inventory was not used to confirm these
findings because, though it provided coordinate infor-
mation for each sign, the coordinates are to a point
randomly sited within the parcel containing each sign,
not to the sign’s exact location within the parcel.
Hence, my field location points were more accurate.
Given that urban planning is focused on individual
parcels, the second result sought was whether web en-
tries were sited within the correct parcels. ArcMap is
capable of determining if a point is within the bounda-
ry of an areal feature or an adjacent areal feature, but
parcels are often separated by streets and sidewalks.
To assure the findings were accurate, a manual analysis
was necessary. For this, I used Los Angeles County’s
parcel dataset, visually comparing the parcel that con-
tained a web entry and the parcel that contained the
corresponding field point (Figure 5). Even with 91% of
web entries within 100 ft. of the correct location, this
test revealed that only 50% of web points were sited
within the correct parcel, 88% were located in the cor-
rect parcel or within one parcel of the correct one, and
98% were located in the correct parcel or within two
parcels of the correct one. The disparity between posi-
tional accuracy and correct parcel placement is ex-
plained by the urban setting of Los Angeles, as the
commercial corridors which host outdoor advertising
are often lined with narrow parcels. This level of accu-
racy is likely not good enough to be considered viable
for LADBS’s purposes in regulating signage, as signage
is permitted based on parcel.
Figure 4. Sample image of ArcMap with line measurements between web and field data points.

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 82
Figure 5. Sample image from ArcMap with web point separated from corresponding field point by one parcel.
The Billboard Map relied on users to manually enter at-
tribute information including the number of sign faces,
and whether a sign was lighted or digital. In the majori-
ty of cases, these fields were left empty. The finding is
in line with existing studies of VGI. OSM’s positional
quality far exceeds the quality of other attributes
(Girres & Touya, 2010; Haklay, 2010; Zielstra & Zipf,
2010).
The temporal quality of the website’s data was in
large part dependent upon the temporal quality of the
GSV data. Although the website allowed a user to enter
a sign whether or not it was actually shown in GSV, no
users during the test period did so. Although GSV data is
updated, on average, every 18 months, a review of GSV
in Los Angeles shows that the data has been updated
every three to six months for the last three years. The
inventory of billboards created by the City of Los Ange-
les, on the other hand, is conducted every two years.
The spatial data quality assessment was run on 326
signs, and, given that the estimated number of off-site
signs in Los Angeles at the time was 10,000, it was clear
that the Billboard Map data was incomplete. However,
the entry rate of the data suggests that completeness
would be an on-going issue. According to the city’s 2014
inventory, there are 8,814 off-site sign faces within the
municipal boundaries. In the first three months of oper-
ation, the Billboard Map contained 431 sign faces (105
of the 326 signs were double-faced signs). At a rate of
431 in three months, it would take years for the public
to map the nearly 9,000 sign faces in the city.
As in OSM datasets, the Billboard Map’s complete-
ness varies over space. Whereas OSM coverage drops
from urban to rural areas, the Billboard Map dataset
varies across the urban setting. Most users entered on-
ly one sign, but a few users entered many signs along
one stretch of roadway. Accordingly, most parts of the
city were unmapped while a few corridors have near
complete coverage. For instance, one registered user
entered 56 sign faces along a 2.2mile stretch of Mel-
rose Boulevard, making the coverage in this area much
more complete than in other parts of the city.
The spatial data quality factor that separates the
Billboard Map most noticeably from other VGI studies
is over-completeness. Unlike OSM users, the users of
the Billboard Map entered excess data points. First,
they mapped signs that were outside the municipal
boundary of Los Angeles. The city of Los Angeles com-
prises a large, awkwardly shaped area, with numerous
smaller municipalities within its bounds or adjacent to
it. Some of the cities, such as West Hollywood, which
contains the famed Sunset Strip, and City of Industry,
have much more lax regulation of signage than the city
of Los Angeles. With the proximity of the cities and the
size of signage, outdoor advertising that sits in, and is
therefore regulated by, one city can easily be seen
from other cities.
The aspect of over-completeness that is most strik-
ing is the type of signs mapped by volunteers. Billboard
Map users mapped signs that were not of the type
identified in the city inventory. City inspectors record-
ed only the traditional style of off-site signs, the pole,
wall, and roof signs known in the vernacular as “bill-
boards” (Figure 3). The VGI dataset of the Billboard
Map includes many types of signs beyond these tradi-
tional billboards. These include massive signs integrat-
ed within new architecture (Figure 6a), supergraphics
wrapped around older structures (Figure 6b), signs
posted on fences (Figure 6c), and wall signs of larger
dimensions that older wall billboards (Figure 6d).
Judged against the city’s inventory, these signs are ex-
cess data that undermine the spatial data quality of the
dataset.

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 83
Figure 6. Sample Google Screen View images of Billboard Map entries, showing “excess” data points of signage not col-
lected by city inspectors.
5. The Ontology of Off-Site Signage and the Ontology
of the Landscape
Though LADBS limited its inventory to traditional pole,
wall, and roof billboards, the legislation creating the
program does not so limit its scope. The inventory or-
dinance states, “All off-site sign structures as defined in
Section 14.4.2 of the LAMC and subject to the provi-
sions of Chapter I of the LAMC are subject to regular
inspection” (Off-Site Sign Periodic Inspection Program,
2014). Chapter I of the LAMC regulates development on
private property but not government-owned property,
hence the inventory is only of signs on private property.
Section 14.4.4 defines an off-site sign structure as, “A
structure of any kind or character, erected, used or
maintained for an off-site sign or signs, upon which any
poster, bill, printing, painting, projected image or other
advertisement may be placed” (Sign Regulations, 2008).
Notably, this language does not limit an off-site sign to
traditional pole, wall, and roof signs. According to the
language of the statute, therefore, the inventory should
include any structure used for an off-site sign.
On closer inspection, the “excess” Billboard Map
data appear to fit within this broad definition. These
signs show ads for banking services draped down the
sides of an office tower (Figure 6a) and wrapped
around the top of a touristic gift shop in the heart of
Hollywood (Figure 6b); they show ads for phone service
on the fence around a car repair shop (Figure 6c) and
liquor on the exterior of a butcher shop (Figure 6d).
Therefore, these signs are “off-site signs” according to
the city’s definition and thus within the mandate of the
city’s inventory.
The discrepancy between the city residents’ and in-
spectors’ compilations of off-site signs appears to be
based on differing ontologies of the two projects. The
users of the Billboard Map website had a different con-
ception as to the scope of signs to be mapped than
that of the expert field inspectors working for the city.
Somewhat ironically, inspectors for the city’s “Off-Site
Sign Periodic Inspection Inventory” only mapped a lim-
ited collection of off-site signs. For the Billboard Map,
city residents mapped all kinds of off-site signs.
In fact, many types of off-site signs exist throughout
the Los Angeles landscape in addition to traditional
billboards. As noted, the city banned new off-site signs
in 2002. Also in 2002, the city signed a contract with
global outdoor advertising company JCDecaux for
street furniture adorned with off-site signage
(JCDecaux, 2002). Soon after, hundreds and then thou-
sands of new off-site signs appeared across the city
pursuant to this program. Because the inventory ordi-
nance limits its scope to private property, these signs
are not technically within its scope as they sit on public
sidewalks. In addition to the ban on new off-site signs
and the inventory program, the 2002 sign laws enacted
a new zoning mechanism entitled Sign Districts, and
the city soon enacted the first such district, the Holly-
wood Signage Supplemental Use District (2004). In the
following years, the city permitted more than fifty off-
site signs, most of which were supergraphic signs,
spanning whole building walls. Billboard Map users
mapped many of these signs, including those shown in
Figure 6a and 6b. In 2007, the city allowed off-site signs
on walls placed around construction sites and undevel-
oped lots, under the deceptively entitled Graffiti

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 84
Abatement Program (2007). These walls are intended
to be temporary but without enforcement by the city
and because they give a financial incentive to property
owners to keep their parcels undeveloped, these often
become permanent fixtures of the cityscape. Figure 6c
shows one such signed mapped by a resident. Not long
after the temporary construction wall sign ordinance
was passed, the owner of the company that lobbied for
the signs began erecting off-site signs under the cover
of a law that permits temporary promotional signs.
These signs feature small text along the sign frame
stating “Come into (name of on-site business) and en-
ter our sweepstakes for a chance to win these or relat-
ed prizes”. The sign faces, however, always display off-
site advertisements, and are never images related to
an on-site sweepstakes or other promotion. A number
of these were also identified in the Billboard Map, such
as that shown in Figure 6d. In 2011, the city entered in-
to a contract with Martin Outdoor Media for bus
benches adorned with off-site signs, and thousands of
these signs now fill the city. The image in Figure 6d
shows two such benches in the foreground. Like the
JCDecaux street furniture signs, these sit on public
property and are thus beyond the scope of the inven-
tory mandate.
This list reveals the vast difference between the
scope of the mapping project as understood by the
Billboard Map users and the scope the city inspectors
were tasked with. The discrepancy is due not just to
different ontologies between the two mapping projects
but to different ontologies as to the landscape itself.
The Billboard Map data reveals that city residents view
the urban landscape very differently than do city
agents: urban residents view the landscape as a cohe-
sive whole, while city agents view a landscape of cate-
gories. Landscape scholars argue that landscape is a
“way of seeing” (Cosgrove, 1984), as much cultural as
material. Landscapes are therefore open to interpreta-
tion as well as contestation. The disparity between the
lived experience of landscape and the expert, planned
conceptions of landscape (Mitchell, 2003; Mustafa,
2005) might explain why urban residents view the
landscape differently than the city agents who regulate
it. LADBS inspectors are tasked with enforcing specific
code provisions, granting permits for individual pro-
jects, counting and cataloguing each of the thousand of
off-site signs. They labor in the minutiae of the munici-
pal code, and, in their working lives, the landscape is a
categorical one.
The broader issue, though, is with the setting of the
categories themselves. “Where competing accounts of
what constitutes the categories of landscape exist, the
fixing of those categories is an inherently political exer-
cise” (Robbins, 2001, p. 162). The power inherent in
the setting of landscape categories derives from the di-
alectical relationship between the cultural and materi-
al. Those who set the categories can remake the
landscape accordingly. This dialectic, and the power to
remake the landscape according to a changing ontolo-
gy, is evidenced in the Los Angeles landscape. In 2002,
Los Angeles banned new off-site signs following years
of community protestation against the landscape of
advertising (Pelisek, 2008). In the years following the
ban, the city approved new categories of signage includ-
ing street furniture, temporary construction wall, and
bus bench signs, and then outdoor advertisers added
thousands of new signs to the urban landscape pursuant
to these categories. The city created the Hollywood Sign
District in 2004, and it thereby permitted fifty massive
new off-site signs to adorn development projects that
are visible for miles outside of the sign district itself. By
remaking the categories of landscape, the city decision-
makers have remade the landscape itself.
In 2010, the Hollywood Sign District was effectively
cancelled due to public backlash against the changes to
the landscape. Yet the city’s creation of new categories
of signs continues. In 2011, the city approved a new
sign district in the heart of its downtown that will allow
a massive new development project adorned with off-
site signage. At a public hearing before the City Coun-
cil’s Planning and Land Use Committee (2011), then-
City Council member Jan Perry stated in support of the
project, “What is being proposed by the developers is
not a billboard”, thereby distancing the proposed signs
from the cultural baggage associated with the tradi-
tional categories of off-site signs. However, the Bill-
board Map shows that the residents of Los Angeles
understand the landscape as a cohesive field of adver-
tising, not as the collection of regulatory categories
under which these signs are permitted. Whether the
City Council deems these new signs “billboards” or not,
residents see them as more off-site signs.
6. Conclusions. VGI for Improving Expert Data and
Community Knowledge
The Billboard Map website was envisioned as a method
of collecting data for the city’s off-site inventory in the
years that the program was politically stalled. The head
of the inventory program was skeptical at the outset
about the utility of the data for the city’s purposes (L.
Zamperini, personal communication, June 22, 2011), a
common governmental response to VGI (Johnson &
Sieber, 2013). On first look, Mr. Zamperini’s skepticism
is borne out by the results of the spatial data quality
analysis, as the non-expert mappers did not under-
stand the scope of the city’s inventory project and
mapped far more types of signs, yielding a dataset with
excess data. To make the Billboard Map’s data match
the scope of the city’s inventory, a future iteration of
the project could employ a filter on sign type to limit
the types of signs mapped by users or to require volun-
teers to complete a tutorial prior to mapping. Scholars
note that stricter rules for collection of VGI can im-

Urban Planning, 2016, Volume 1, Issue 2, Pages 75-87 85
prove the quality of spatial data (Girres & Touya, 2010;
Haklay, 2010), yet scholars also suggest caution in ap-
plying rules so as not to stifle creative and unconven-
tional map-making (Van Exel et al., 2010). The Billboard
Map VGI shows that the creativity of non-professionals
reveals itself in unlikely ways. The spatial data sought
here—off-site signs—is straightforward. Signs are
large, material structures, not ephemeral happenings.
The project was not designed to collect opinions or
ideas about signs (Rinner et al., 2011); it was not de-
signed to map emotions about signs (Kwan, 2007); it
did not ask residents to envision future spaces with or
without signs (Seeger, 2008). Yet from the simple map-
ping task undertaken by so-called sensors, we learn an
unexpected insight about how residents experience the
urban landscape. This finding supports the argument
for caution in applying filters or other rules for data
collection in VGI projects.
Further, by inadvertently ignoring the city’s cate-
gorical distinctions, the users of the Billboard Map have
pointed out that the so-called “Off-Site Sign Periodic
Inspection Program” is a vastly incomplete record of
off-site signs in the city. It may be that the discrepancy
between the city’s actual landscape of off-site signs
and the city’s inventory of off-site signs is an inadvert-
ent error. Just as we can imagine technical rules for
improving the quality of the Billboard Map dataset, we
can imagine instructing LADBS inspectors to correct the
scope of the project to match the language of the ordi-
nance. Yet the scope of the inventory appears quite in-
tentionally limited; in fact, a number of off-site signs
beyond pole, wall, and roof signs were listed in the
2012 inventory but removed in 2014, including the
massive off-site signs on the “Hollywood and Highland”
development that is now home to the Academy
Awards show and an upscale shopping mall. The out-
door advertising industry has great influence in Los An-
geles City Hall, and legislators repeatedly push for
growth of signs and lack of transparency at the behest
of the industry (Pelisek, 2008; Smith, 2012). The crea-
tion of new sign categories to avoid the ban on off-site
signs has been a tactic of urban and industry decision-
makers. The inventory itself obscures the fact that
many of the pole, wall, and roof signs in the city are
unpermitted and illegal (Sedano, 2016). The limited
scope of the inventory to only a handful of the many
types of off-site signs that now adorn cityspace ap-
pears to be another tactic in this overall strategy.
The political backdrop of outdoor advertising in-
spires a different viewpoint on the question of whether
to include spatial data quality rules to improve the vol-
unteers’ mapping of signs. Asking residents to map
signs according to the city’s limited ontology is to en-
gage them in the Sisyphean task of helping a city ap-
pear to regulate without actually regulating. Much
more useful is for residents to continue to map signs
according to their experience of cityspace. A map of
the actual extent of off-site signage in the city could be
incredibly useful in countering the conjoined efforts of
capital and state to grow the advertising landscape, of-
fering a rebuttal to the city’s categorically limited yet
politically acceptable inventory.
As outdoor advertising grows in Los Angeles cit-
yspace, it spreads in cities around the world. Indeed,
companies such as JCDecaux, which have remade the
Los Angeles landscape, are remaking the urban land-
scape globally by coordination with local agencies (Ive-
son, 2012). Los Angeles residents have alerted us to the
fullness of signage that is obscured by categorization.
The global nature of the industry requires future study
to discover whether these tactics are employed
throughout the world to spread signage, perhaps un-
covering the growth of advertising obscured by the lo-
cal nature of sign regulation. Engaging urbanites to
map the full extent of signage is a counter-tactic avail-
able when officials lack the political will to regulate the
advertising landscape.
Acknowledgments
Many thanks to John Given, Daniel Goldberg, Dennis
Hathaway, Karen Kemp, Su Jin Lee, Reid Priedhorsky,
Kaveh Shahabi, and John Wilson for their support of
this project.
Conflict of Interests
The author declares no conflict of interests.
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About the Author
Elisabeth Sedano is a Lecturer with the Spatial Sciences Institute of the University of Southern
California.