Integrating Airport Geographic Information System (GIS) Data with Public Agency GIS (2014)

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24 chapter four CHALLENGES TO DATA SHARING AND STEPS TO OVERCOME THEM Despite the overwhelming desire for more centralized, readily accessible data and the growing range of web-based options to satisfy that desire, many airports and public agencies face challenges that con- strain their ability to get the data they need. The reasons can be technical or organizational, although most reported that technical challenges are easier to address and that organizational challenges far more difficult to overcome. Often respondents indicated that they would be willing to pay to develop these data in-house, because it is important to their needs, yet found it difficult to obtain the funds necessary to do so. Figure 14 indicates some of the more prevalent factors that prevented respondents from getting the data they desire. The “other” category includes references to data quality, accessibility, and concerns over sensitivity. This chapter provides detailed description of the types of challenges that airports and public agencies report facing and the means some have used to overcome them. ORGANIZATIONAL CHALLENGES As mentioned earlier, most respondents identified organizational factors as the greatest challenge they face when exchanging data. It is human nature, and often a fiduciary obligation, to prioritize one’s own organizational needs over another’s. Some individuals also believe that sharing infor- mation they possess diminishes their relevance. Barry Wellar suggests that “much of [this atti- tude] has to do with power, prestige, and empire-building on the parts of individuals and agencies wanting to ‘run the show’ ” (Wellar, p. 42). Airports and public agencies are also governmental organizations that face budgetary constraints, restrictions, protocols, and organizational complexi- ties that do not inherently foster data exchange. Some agencies reported that they felt pressured to recoup data development costs by charging for the information, although the trend is toward providing data for free (Wellar, p. 43) or at a “cost not to exceed the direct cost of duplication” (California Supreme Court 2013, cited later in this chapter). Other agencies have tried, despite the Freedom of Information Act, to withhold data (Sierra Club v. The Superior Court of Orange County 2013, also cited). Some data are, however, considered sensitive or proprietary and cannot be widely shared. Because of organizational complexities, data exchange is enhanced and more easily accomplished if an airport is a part of a municipal or county agency. This is especially true when resources beyond data, such as software, hardware, and human resources, are also shared. This is likely because of less challenging logistical hurdles or a sense of responsibility among entities within the same organization. Fortunately, as indicated in interviews with airports and municipalities in this study, there is a clear trend away from a restrictive approach to sharing data because of legal restrictions and impos- ing fees to a more open approach, making data easily searchable, free, and without restriction. Some agencies are legally required to provide data without restriction (New York State, p. 1). Some are managed by individuals who believe it is their professional obligation to share their resources with peers and with the general public. Others have come to the conclusion that the cost of preparing and disseminating data on request is greater than that of simply publishing it on the web. Whatever the reason, the trend toward open data is growing (as indicated by the increasing number of organiza- tions doing so and the amount of recent literature and discussion on the topic) and it is resulting in a greater volume of information openly available on the Internet.

25 Open data exchange also frees agencies of the burden of developing and enforcing written agree- ments that many have (and some still) require. Some states, such as Florida, have determined that data developed using taxpayer money could be made available to the general public on demand. Similarly, the California Constitution states that “the people have the right of access to information concerning the conduct of the people’s business” [Article I, Section 3, Subdivision (b)(1)]. Because of these decisions, there is an increasing amount of geographic information and related resources on government websites that can be downloaded by citizens and companies alike—with, at times, restrictions. Some organizations are encouraging the philosophy that data should be shared unless told otherwise, which is the opposite of assumptions in the past. Several respondents noted that passionate GIS professionals will go out of their way to help pri- vate citizens, peers, and colleagues find the resources they need. However, the following are some of the challenges organizations have reported facing, and ways they have overcome them. Cumbersome Agreements Although digital and/or written agreements have traditionally been common in data sharing transac- tions, there is a clear movement away from the cumbersome and time-consuming efforts of generat- ing and enforcing data sharing agreements. This trend was not only identified by respondents to this synthesis and literature reviewed, but found as a part of the review behind ACRP Synthesis 48: How Airports Measure Customer Service Performance (Kramer et al. 2013). Some organizations, however, still see the need for formal data sharing agreements and are tak- ing steps to facilitate the process with standardized agreements. Cy Smith, Oregon GIS coordinator, noted that “in the past, formalization was seen as too difficult and legalistic, but several obstacles have presented themselves over the years that virtually require formalized data sharing agreements between organizations” (Wellar, p. 44). He and his colleagues have therefore taken steps to ease the process of FIGURE 14 What factors have prevented you from getting the data you require? Source: 24 of 44 survey respondents.

26 developing agreements by providing a matrix that helps identify restrictions that can be referenced in standardized data sharing agreements. A few airports and several public agencies indicated that they have had or still have written agree- ments that data requesters were asked to sign before information could be shared. In some cases, these agreements took the form of non-disclosure agreements (see the Savannah Airport case example in chapter five). In other cases, a memorandum of agreement or a formal contract was put in place. Some organizations indicated that the cost of developing and enforcing these agreements was greater than the protection they believed the agreements afforded, and in the end decided to make data openly available. Sometimes terms and conditions will be placed on the website where data are available for users to accept, actively or passively, upon download. Excessive Protection of Sensitive Data Data security is a technical as well as organizational challenge. It is included in this section because data providers indicated that the organizational challenges of data security are harder to overcome than the technical ones, especially in the post-911 era. Technical challenges of implementing data security can be overcome with modern user authentication, encryption, and other techniques; this is the focus of ACRP Project 05-02, “Airport Cyber Security Best Practices.” Organizational challenges regarding data security include requiring training, consideration of cultural changes, policy adjustments, assessing the tradeoffs between security and accessibility, understanding and weighing technical options, and balancing budgetary constraints. However, although some data sets warrant high security, others do not (Baker 2004). Sensitive Security Information (SSI) is defined in the Code of Federal Regulations (CFR, Title 49 Part 15.5) as information obtained or developed in the conduct of security activities; and by law, must be protected. Other data, such as utilities mapping, may also warrant an increased level of protection because of the harm that could be inflicted if this information were available to wrongdoers. Many organizations seg- regate publicly available data from SSI and other sensitive data information that require users to agree to specific terms and conditions through an official channel from publicly available data. Accessing protected data requires users to agree to specific terms and conditions through an official channel. Public data are openly available for search and download. Seldom are additional distinctions made, making administration easier for staff. Data security measures may also apply if licenses, copyrights, or other restrictions have been placed on a data set by vendors or other providers. Legal Constraints In some cases, data providers cite legal restrictions, such as confidentiality, copyright, and licens- ing restrictions, as deterrents to sharing data. In many cases, these constraints are valid and protect sensitive information or the intellectual property rights of organizations that have paid considerable amounts to develop the data. Public agencies recognize the need to segregate such information from data they freely distribute, and to impose the necessary restrictions so that legal constraints are not violated. This creates a dis- incentive to data sharing, as the benefit must exceed the added cost of providing it within the legal restrictions in place. Airports report this problem less frequently, primarily because the data they require is either developed in-house or does not carry such restrictions. In some cases, agencies that limit data sharing based on sensitivity or confidentiality exceed their authority to do so. A few respondents speculated that these restrictions were used as excuses to retain control over data for fear it might not be of a high enough quality, etc. As an example of excessive limitations on data sharing, Orange County, California, asked the Sierra Club to pay $475,000 for data it had requested, and restricted its use and distribution. In 2013, after 51 months and two lower court rulings in favor of the county, the California Supreme Court ruled that Orange County must provide its parcel data to the Sierra Club “in any electronic format in which it holds the information

27 at a cost not to exceed the direct cost of duplication.” Although this case is somewhat unusual, it may be precedent-setting. Legislation in the state of Florida, however, offers a different example that accentuates an open data philosophy. In 2013, state lawmakers in Florida delivered new policies and laws intended to make government more open, ethical, responsive, and accountable. Title X, “Public Officers, Employees and Records,” Chapter 119.01 “Public Records” statutes clearly state that “all records are open for personal inspection and copying by any person. Providing access to public records is a duty of each agency.” This statute, along with digital distribution and Internet advancements, has made Florida one of the jurisdictions most advanced in making data readily available to the public. Not all states have embraced open data laws. Lawyers are therefore left to advise their clients based on a variety of interpretations, often without precedent. It was stated by interview participants that when requested for opinions where data sharing laws are not present, legal counsel tended to default to advising agencies and organizations to prohibit or avoid data sharing because of perceived risk as well as because of traditionally conservative positioning on this general topic. It was also suggested that if equal energy were expended on encouraging data sharing, more constructive exchanges would likely evolve throughout the nation over time. Lack of Formal Procedures and Policies Many airports and public agencies responded that they benefitted from written policies and proce- dures that support data maintenance and sharing. Other organizations, however, have not committed the time or resources to develop such procedures or policies. Some public agencies have benefitted by being a part of larger municipal, county, or state agencies that already have policies and procedures that they can adopt. New York State, for example, has a policy that “encourages public agencies to share in the creation, use, and maintenance of GIS datasets at the least possible cost, while providing citizens, the media, and other data users easy access to this resource” (New York State 1997, p. 1). Airports are less fortunate in that much of their data needs are unique to aviation operations, mak- ing public agency documents less relevant. Airports do, however, have FAA Airports GIS standards which are applicable to their unique needs. Some airports have developed policy and procedures based on the FAA standards, and others have augmented their procedures with relevant details from public agency documents. Disconnected Organizations Many airports indicated that they are part of city or county agencies that have GIS data and resources to offer, but only a few of them take full advantage of these resources. For example, numerous cities and counties have enterprise licenses with software and data vendors, but only some agencies are willing to host applications for airports or other constituents in their region. Several of the airports and agencies interviewed found it easier to identify and obtain data when they come from within their organization, their parent organization, or a peer organization under the same governing body. When the requests crossed organizational boundaries, differing budgets and policies tended to hinder data exchange. Many respondents report overcoming this by developing relationships with peers in other agencies, thus building trust and increasing the willingness of GIS data providers to provide data to colleagues in other organizations. Limited Staffing Most organizations indicated that only a few employees are dedicated to data maintenance and/or exhibit production. Additionally, municipal agencies have been hit with budget cuts over recent years that have led to noticeable staff reductions. Extracting and copying data into an acceptable medium often consumes too much time and becomes a barrier to data exchange. Some agencies have found it

28 easier and less costly to simply make data freely available to those who need it through downloads, WMS, or other means. (This is another incentive for publishing data by means of WMS or FTP sites, as described in chapter three.) A less technical solution is to rely on assistance from other organizations. Some airports, as noted, “borrow” GIS staff from a municipal or county agency. Although exemplary, these situations of cross-agency labor-sharing are the exception, not the norm. A Lack of Collaborative Forums Many regions reported having organized forums that regularly bring together like-minded participants to collaborate and network. The benefits of such collaboration are seen in most of the case examples in chapter five, especially those of Denver, Las Vegas, and Minneapolis. Most of the time, the dis- cussions identify data needs and other common requirements; seldom do they go into detail about specifications or formats. Instead, participants share success stories, develop contacts, and delve into specific requirements outside of these forums. In a few regions, subcommittees have been formed to regularly discuss specific topics of interest. In most cases, these forums are free to participants; in other cases, the forums are nonprofit opera- tions paid by membership fees. Because they are typically supported by volunteers, these forums may lack participation from senior managers and local political leaders who could implement changes in data sharing policy. In regions with particularly active and effective forums, there are typically one or two GIS profes- sionals who have championed a data sharing initiative for years and who are credited with establishing and nurturing a culture of collaboration. Individuals with energy and passion can have a significant impact by helping to establish and direct the focus of committees, meetings, and user groups in ways that the regional GIS community finds valuable. At times, however, GIS professionals indicate that they do not perceive that there is sufficient value in participating in these forums. This appears particularly true of airport GIS professionals, who are increasingly busy and resource-constrained; at the same time, they perceive their needs as being different from others in their region. Some also perceive themselves as having unique needs that can be met internally, without the need to reach out to peer agencies. They therefore elect not to participate; in some cases, management does not support their participation. Some also perceive that participation would generate additional work, or that they would be “giving” more than “receiving.” Whatever the reasons, it is clear that airport representatives participate less often in these forums than their peers in nearby public agencies. Airports do value the usefulness of national conferences that focus on the specific subject of airport GIS. Airports that have sought assistance from city or county agencies have typically been smaller and without adequate funding and/or human resources to develop the GIS capabilities they desired. Those that have utilized the resources of nearby agencies report a cost savings that has justi- fied the effort to collaborate. Limited Awareness Among Those Who Can Affect Change GIS advocates and users have reported difficulties in conveying the importance of their recommenda- tions to senior managers and political leaders who could implement changes in data sharing policy. They often have trouble conveying the broader relevance of their message, recognizing that it is detailed and technical. One GIS advocate believes that it is sometimes easier to get support for aerial imagery because it is visual and broadly used, as opposed to detailed vector data and attributes that can support more valuable analysis. The solution suggested by respondents is for GIS advocates to learn to “market” their ideas to management and political leaders more effectively. Educating these leaders about the benefits of data

29 sharing and GIS collaboration can be very effective. Summarized recommendations written in a non- technical way and supported by cost/benefit justification have proven to be very useful. Lack of Executive-Level Champions A growing number of airports have established GIS manager positions to centralize their GIS data, systems, and human resources. These managers help champion the importance of GIS, synergize resources, and provide a focal point for external data sharing. Individuals in this role are particularly empowered when they report to an executive who supports an open data philosophy (as discussed previously). An increasing number of states, including Arkansas, New York, and Maryland, have appointed a Geographic Information Officer (GIO) under the governor who has statewide jurisdiction in promot- ing GIS concepts, coordination, and values, including data sharing protocols. Individuals in these positions can establish policies and standards to promote data sharing. Some GIOs have set up com- mittees to promote GIS capabilities of agencies within the state. They also foster GIS collaboration and data sharing as part of efficiency initiatives within government. Costly Collaboration and Sharing Adjusting data to conform to standards, adding relevant or removing irrelevant attributes, and enter- ing metadata so that data can be used by others takes time and is therefore costly. Even when GIS users support data exchange, they still face the challenge of securing and prioritizing already limited resources to enable it. The result limits data sharing or requires recipients to take data as-is and expend their own resources to make any necessary improvements. The challenge of justifying the cost of data exchange is reduced when the exchange is recipro- cal. If by providing data to others, GIS users also receive data that they value, then the benefits of data sharing increase to help justify the costs. Similarly, data providers may be encouraged to share data because it allows them to receive capabilities, services, or other benefits in return. If an equally valuable exchange is not possible, then recipients or governing bodies that represent the interests of recipients must provide the necessary funding. Examples of this have been seen when an agency that requires data provides funding to an airport to collect the data its needs, or when a state or local gov- ernment provides funding for GIS staff to disseminate data to constituents. Some data providers offset the cost of sharing data through nominal fees, as is the case with subscription-based and one-time payment plans. Data sets that require payment typically require that the data not be resold or redistributed. Although understood by most users, this restriction does reduce the dissemination and use of the data. TECHNICAL CHALLENGES Airports and/or public agencies also face technical challenges when trying to share data. Although modern technology offers many solutions, technical, financial, or organizational constraints render some unfeasible. For each technical challenge identified, the solution(s) some organizations have found successful are reported. Lack of Consistently Applied Standards Standards can address the specifications to which data are collected, the structure of the data, or the level of attribution and metadata. However, several examples where identified where information the respondents obtained from another organization was difficult to use because it did not conform to a common standard. In such cases, some airport staff members indicated that they had to adjust the data they receive, whereas others have left the data as is and worked around the differences. Not all the data sets were relevant to the airport; but for some purposes, as when parcels are used to identify

30 land ownership for sound insulation programs or land acquisition, the data are essential, so these dif- ferences can become problematic. Some larger public organizations, such as the Denver area’s North Central All-Hazards Region (see the case example in chapter five), have been successful in establish- ing regional standards that help homogenize data sets, especially those addressing street centerlines and addresses that need to be consistent across municipal, county, or even state boundaries. These standardization efforts are especially beneficial at the regional level where agencies from abutting jurisdictions need to share data with one another. Some public agencies have also participated in national initiatives to standardize addresses for emergency response purposes. At this level, not only might it be possible to exchange information with nearby agencies but with national emergency response and other initiatives. Unfortunately, national standards developed to support specific categories of data are often underutilized (Wellar 2010). Information that does not adhere to common standards, or to any standards at all, increases the difficulties of data exchange because data recipients must adjust data to meet their needs or live with the differences. An example of this is the challenge airports have faced when integrating land use data from multiple jurisdictions, as discussed earlier. This consumes time and therefore costs money. Data providers also have expressed concerns that these adjustments may degrade the quality of the data they have provided and that they might be held accountable. (The concern over deriva- tive products is discussed further later in this chapter.) Airports reported struggling with data consistencies less often than public agencies for two reasons: First, airports rarely if ever need to exchange data with other airports and typically only exchange a few data sets with local public agencies upon request. Such data are often exchanged as-is. Second, the FAA Airports GIS program defines data standards for approximately half of the data sets main- tained by larger airports and a larger proportion of the data sets maintained by small and medium- sized airports. Although the required transition to these new standards is not complete (DeLeon and O’Donnell 2012), all airports interviewed are aware of them and many are already moving toward compliance. This movement toward common criteria for airport data is beginning to become a perva- sive industry practice. Unlike airports, public agencies are not typically required to adhere to particular data standards. In some regions, agencies report having adopted a common standard for street centerlines and address- ing to facilitate compatibility with neighboring communities. Several public agencies have partici- pated in Emergency 911 initiatives at the state and federal levels that prompted them to comply with broader national addressing standards. Martha Wells of Spatial Focus, Inc., reports “URISA under- took the preparation of an Address Data Standard for the [Federal Geographic Data Committee], and this standard is now nearing full adoption. Many jurisdictions—local, state, regional, and even federal—have been asking for and even using [this] standard” (Wellar 2010). Figure 15 indicates the factors that influence the definition of standards at airports and public agencies. Most of the time, internal customers and/or management drive the development of stan- dards. Very few agencies reported that their standards are driven by federal or state government, but some indicated that external customers are a factor. A number of airports mentioned adhering to the FAA’s Airports GIS Standards, but did not believe that the FAA requirements influenced the develop- ment of or updates to the majority of their data. Poor Data Quality The evaluation of data quality encompasses positional accuracy, temporality (i.e., time and frequency of update), comprehensiveness, level of attribution, correctness of attribution, presence of metadata, and other characteristics. Data quality requirements vary widely by data set, steward, intended use, project, and organization. Airports typically respond that they have higher requirements for spatial accuracy than public agencies, reflecting the relatively large map scale they require, as well as an engineering perspective that necessitates precision. Public agencies often favor comprehensiveness and consistency, because they must integrate disparate data sets from multiple jurisdictions in order

31 to support the regional analysis their users require. The result is that not all data exchanged is of equal quality, and may lack metadata context. When data are exchanged, receivers typically take what they can get and then adapt the data as effectively as they can to their needs. Metadata becomes critical to the usefulness of data but is seldom available. This increases the cost of using the data, as it must be evaluated and sometimes improved before it can be used. Regardless of the level of metadata, reported best practices suggest that caution be used when applying data from unknown or even known sources. Out-of-Date Data One element of data quality that was frequently emphasized by respondents was temporality, or the degree to which data has been kept up to date. Figure 16 shows how often data recipients require data to be updated. Most respondents indicated that they update their data on a project-by-project basis or when it is requested. This approach can work when the requestor and provider are within the same organization and the importance of the request warrants the cost of updating the data. When data are exchanged between organizations, they are often provided as-is. Some agencies, however, reported that core data sets such as road centerlines, parcels, and addresses are continuously updated because of their importance and the number of people that rely on them. Some data sets are kept more up to date than others. Many larger airports and public agencies update aerial imagery and terrain data annually or biannually. Parcel data are continuously kept up to date by county assessors, but may not be readily accessible in a GIS format. Periodic and widespread use of the data is what drives demand for continuous updates. One interesting observation shared by an agency was that data published through web services appears to be more up-to-date than that from other sources. The agency’s theory is that providers who publish data by means of the Internet do not know who is using it, when, or how often, so they feel obligated to keep it current. As more data providers implement web services, it is like that a trend toward continuous updates versus as-needed revision will develop, resulting in an increase in the temporal accuracy of data. FIGURE 15 Drivers of standards. Source: 25 of 44 survey respondents.

32 Improper Derivatives Public agencies often indicated that they need to adapt the data they receive from others to meet the needs of their users. Airports do this less frequently, perhaps because the majority of their data comes from internal sources and has been developed to meet their specific needs. Some data providers expressed concern that data they share could be inappropriately altered by recipients, thus degrading its quality or violating copyright or licensing restrictions, and make the providers culpable for conclusions drawn from the altered data. Some providers or data originators will allow users to implement and alter the data for their own purposes but prohibit providing the altered data to others, even if they have similar needs. Concerns over liability or accountability for decisions made based on these derivative products have increased their hesitancy to share data. In other cases, data owners fear that derivative products will not be used properly and therefore reflect poorly on their organization or their data. Conversely, recipients of data have expressed frustration about the need to alter data to meet their needs. This adds cost, especially if the data are periodically updated. They too fear being responsible for degrading the quality of data, especially when it is not within their domain of expertise. Providing data through web services that restrict ability to alter content; creating metadata that clearly states how data are to be used; and legally restricting inappropriate use of data may be effec- tive responses to this problem. Lack of Metadata Metadata provides users with important information about and how to use the data they receive from others; and often such sites protect the provider by defining the limits for use through meaningful disclosures. The Federal Geographic Data Committee (FGDC) Content Standard for Digital Geo- spatial Metadata (FGDC-STD-001-1998) and the International Organization for Standardization’s Geographic Information—Metadata standard (ISO 19115) define a variety of metadata elements that support geographic information. Some agencies such as SANGIS (see the case example in FIGURE 16 How frequently do you require updates of the data you receive from others? Source: 28 of 44 survey respondents.

33 chapter five), recognize the importance of metadata and check all of the data they develop or receive to ensure that it has a minimum level of metadata. Airports have reported that the most important metadata elements, which help them understand how to use the data, include its source, collection method, date of collection, and accuracy. Despite its importance, many airports and public agencies alike report that they do not receive the level of metadata they need or desire. Many data providers do not populate the metadata when adher- ing to best practices. One frequently reason cited for not populating metadata is that it consumes time and money after the primary task of developing the data has been completed. Given that data are often developed or updated to meet project specific needs and that most data are developed to meet an organization’s internal requirements, it is likely that metadata has less benefit to the primary users of a data set, who likely already know what they need to be able to use the data. Such a lack of metadata, however, seriously degrades the ability to exchange data with external users. Some data developers believe it is their obligation to populate metadata, but admit that it is sel- dom done. Evolving metadata standards and, more importantly, tools based on those standards can facilitate the development of metadata. Some of these tools, as well as Extract, Transform, and Load (ETL) software, can automate certain aspects of metadata population. Large programs, such as the FAA’s Airports GIS, also collect a variety of metadata at various levels as grants are issued, projects are created, and quality assurance reports are prepared. WCS also make available more metadata than is typically found in data sets that are not published through web services. Data-Related Differences That Are Difficult to Overcome There is a wide range of incompatibilities—file formats, coordinate systems, projection, or media— that can make data unusable when it is received. Most of these can be overcome by applying the correct mix of transformations. Following are some of the more common interoperability issues reported by respondents: • Coordinate Transformations—Airport architects and engineers often use custom Cartesian coor- dinate systems that align runways with the orientation of the plotted drawing with little account for ellipsoid models or the earth’s curvature. Geospatial data in these coordinate systems can be converted to/from standard coordinate systems if the parameters required to support an accurate transformation can be provided and if the skills to apply these parameters within software capa- ble of such transformations are available. These transformations must account for the horizontal and vertical coordinates and ensure that they are accurately referenced to the proper horizontal and vertical datum to the degree of tolerance specified. Inevitably, some inaccuracy is introduced into these calculations, but it is the responsibility of the individual applying them to understand what level of tolerance is acceptable and to report this as a part of the metadata. In some cases, the lack of human resources has presented a challenge when exchanging data. • Different Format—Geospatial data can be provided in a variety of formats. Although some open standards have emerged, many of these formats are proprietary. Fortunately, proprietary systems and software specific file formats present fewer challenges to data exchange today than they did a decade or two ago. Software vendors will, however, periodically upgrade their underlying data formats or offer new formats to take advantage of emerging technologies. This can create a challenge for other vendors who need to update their software to maintain the abil- ity to read or write to these formats. Extract, Transform, and Load software has emerged over the years to help alleviate the incompatibilities between various formats. • Cumbersome Media—File sizes, particularly of raster imagery, can be so large that they pre- vent the efficient exchange of data. External hard drives or DVD stacks are at times necessary for transferring such large data sets. To overcome this, some counties post DVD binders in pub- lic libraries. Other counties are taking advantage of WMS, which render data on large servers and send out only what has been requested in a much smaller format.