APPENDIX B: QUESTIONNAIRE REPORT
The relatively recent emergence of mobile Light Detection and Ranging (LIDAR) technologies as a potentially transformative tool for numerous transportation engineering applications coupled with a lack of existing standards has resulted in the need for an improved understanding of how this technology is currently being implemented, and what challenges are limiting its adoption. To that end, a web-based questionnaire was administered to State Departments of Transportation (DOTs) in November 2011 to document and evaluate the state-of-the-practice regarding mobile LIDAR in transportation applications. Representatives from each of the 50 U.S. states and 6 additional transportation agencies completed the questionnaire, for a total of 74 responses. Multiple responses were obtained from a few DOTs, which allowed the Team to capture variances between divisions within those DOTs.
This questionnaire provided the Project Team with the data needed to establish a technology adoption baseline for the DOTs by documenting current practices related to mobile LIDAR (also known as mobile laser scanning) use, guidance, and needs.
A second service provider questionnaire was completed by 14 companies experienced with mobile LIDAR services and was administered via telephone interviews. The objective of this questionnaire was to provide additional perspective on the extent of use, and the challenges of adopting mobile LIDAR scanning by the DOTs from a service provider’s perspective. Given the much smaller sample sizes of the service providers, the intent is not to directly compare DOT and service provider perspectives but to provide an outside perspective.
Results from DOT Questionnaire indicate that most agencies have experience with static laser scanning, with approximately 70 % having reported use of the technology for a project in the last 12 months. Most DOTs have also investigated mobile LIDAR to at least some degree and are excited about its potential use in the future. Approximately 50% of the DOTs stated that they have direct experience with mobile LIDAR in one form or another. However, the level of expertise related to mobile LIDAR varies significantly among these DOTs. Interestingly, it was determined that more DOTs have used mobile rather than airborne LIDAR services in the last year, even though mobile LIDAR is a less established and more recent technology.
Most DOTs indicate that they have experience with mobile LIDAR for applications related to engineering survey, mapping, and digital terrain modeling (DTM). These applications were also the top categories selected by the service providers, further confirming the result. Going forward, many DOTs anticipate that in the next 5 years they will use mobile LIDAR data for many other applications in addition to these common applications.
The service provider questionnaire results show that a significant portion (average 60%) of their mobile LIDAR projects involve DOTs and they anticipate that in the next 5 years most DOTs will be using mobile LIDAR data in their workflows.
The top four challenges, as indicated by the DOTs, when working with mobile LIDAR include: software interoperability and data exchange, the size and complexity of datasets, technical expertise, and cost. Additionally, the results showed that DOTs perceive cost to be one of the most significant challenges to the adoption of mobile LIDAR, indicating that more evidence and education are required regarding benefit to cost comparisons of the technology.
Thirty-eight of the DOTs have published surveying and quality control standards. Overall, these DOTs felt that members of their department were familiar with these standards. Some of these (seven) have developed standards or guidelines related to static scanning, while others are in the process. Very few DOTs (Alabama, Arizona, California, and Oklahoma) stated that they have developed guidelines or standards related to mobile LIDAR. This is consistent with the service provider questionnaire results; however, the service providers queried as a part of this effort were only aware of the Caltrans mobile LIDAR guidelines.
Most DOTs believe very strongly that survey accuracy, QA/QC procedures, data interoperability, data management, and software integration are the most important topics to be addressed in the proposed guidelines, with nearly equal emphasis on each topic. In contrast, the service providers felt that QA/QC procedures were by far the most important issue. Most service providers preferred that the DOTs adopt the same standard for mobile scanning rather than develop their own, an additional indicator of the need for the current proposed guidelines.
The questionnaire also revealed current struggles as DOTs transition from two- to three-dimensional workflows and modeling. Regarding 3D workflows in general, many DOTs indicated that they have (42%) or are transitioning (34%) to 3D design workflows. Service providers, however, state that the overwhelming majority of the DOTs have not made this transition. Technical expertise, funding, and organizational issues were reported as the major factors holding back the adoption of 3D workflows, although many other factors were close behind. Service providers stated that the technical expertise and organizational issues were, by far, the top factors limiting the adoption of 3D workflows.
To facilitate further discussion, coordination, data dissemination, and implementation of the guidelines the primary geospatial contact for most of the DOTs were also collected as part of this initial effort.
Overall, DOT and Service Provider Questionnaire show that both DOTs and service providers are very interested in the many transportation applications that can be served with mobile LIDAR. The Project Team believes that developed guidelines will address the primary hurdles identified herein, enabling mobile LIDAR to radically change the transportation industry and aid DOTs with the transition to 3D workflows and operations.
These questionnaires established a technology adoption baseline that can be used to measure future progress and provide the foundation for national guidelines currently under development.
To evaluate the state-of-the-practice regarding mobile Light Detection and Ranging (LIDAR) technology in transportation applications, a questionnaire was administered to U.S. State Departments of Transportation (DOTs) to determine their current usage, interest, and knowledge of LIDAR technology. A key purpose of the questionnaire was to establish an overall technology adoption baseline for all of the State DOTs, which could then be used to develop upcoming, national, performance-based guidelines that address current challenges with mobile LIDAR for DOT applications. A related service provider questionnaire was distributed to experienced surveying and mobile LIDAR companies. Note that due to a much smaller sample size for the service provider questionnaire, direct comparisons should not be made to the DOT responses.
In conjunction with the literature review in the previous appendix, the questionnaire results provide a detailed picture of the current state-of-practice within State DOTs and the service providers offering mobile LIDAR services. The questionnaires also provide insight as to how mobile LIDAR is being considered for future transportation applications so that the guidelines currently being developed will apply to multiple departments and remain applicable over an extended period of time. For reference, complete versions of DOT Questionnaire and Service Provider Questionnaire are presented at the end of this appendix.
B.2.1 Questionnaire program requirements and selection
To facilitate the acquisition of a nationally representative sample of State DOTs and other transportation agencies actively using or planning to use mobile LIDAR, an internet-based questionnaire tool (SurveyGizmo) was selected. Seven free, online questionnaire services (Table B-1) were compared to determine if they met the functional requirements of the questionnaire task for the research project. Zoomerang and SurveyMonkey were the most popular and aesthetically pleasing questionnaire applications reviewed. The professional version of SurveyGizmo was selected as the preferred alternative given that NCHRP synthesis projects are typically implemented through SurveyGizmo. The Project Team believed that this may provide a more familiar platform to DOT personnel who have likely responded to NCHRP synthesis questionnaires previously.
Table B-1: Characteristics of questionnaire tools considered
B.2.2 Potential questionnaire participants
The DOT questionnaire considers a subset of the population of State DOT employees from across the country. The initial contact list of professionals was intended to be individuals from within State DOTs with knowledge in the field of surveying, geographic information systems (GIS), and other geospatial technologies. More specifically, a focus was placed on identifying persons with an interest in 3D laser scanning and modeling. The contact list was not segregated based on departments within the State DOTs. The rational for contacting these specific individuals was to identify respondents who had a useful knowledge base for developing guidelines that reflect the current conditions in mobile LIDAR. The DOT questionnaire was also sent to several federal and international transportation agencies for alternate perspectives. In a further effort to ensure that appropriate respondents were identified, the DOT questionnaire recipients were encouraged to pass the DOT questionnaire along to other colleagues who they believed may be more appropriate to respond.
The second questionnaire was created for and distributed to mobile LIDAR service providers (Service Provider Questionnaire). The purpose of the Service Provider Questionnaire was to obtain further insight concerning the current challenges in providing mobile LIDAR services and the need for performance-based guidelines. This questionnaire was also used to obtain an external perspective of how DOTs are utilizing the 3D data provided by mobile LIDAR.
B.2.3 Level of response
As a result of the keen interest from the target population regarding the questionnaire topic and follow-ups from the Project Team, the overall response rates were high. In total, 74 respondents completed the DOT Questionnaire, representing DOTs from all 50 U.S. states and 6 additional transportation agencies. Forty DOTs responded as a result of the initial email prompt or two additional reminder emails. Subsequent phone calls and directed emails were made to the 10 remaining DOTs to ensure at least one response from all 50 State DOTs. During the data acquisition process, additional contacts were provided by the respondents to the online DOT questionnaire or during the service provider phone interviews. These likely respondents were subsequently contacted to increase the respondent sample size.
Although the results are reflective of the responses that were received from individuals within each DOT, in some cases, the respondents may have been unaware of mobile LIDAR activities and usage outside of their division.
In total, 14 industry leaders were interviewed via telephone to provide each with the opportunity to discuss issues that may not be specifically covered in the questionnaire. Note that although comparisons are made in this report between the DOTs and service providers, equal weight should not be placed on the responses since there were significantly more DOT responses.
The full DOT Questionnaire and Service provider Questionnaire can be found in at the end of this appendix. An example of the online format of these questions is shown in Figure B-1. To analyze the questionnaire results, the response data was exported from SurveyGizmo into spreadsheet for analysis.
Figure B-1: Example of the formatting seen by the questionnaire respondents
B.3.1 DOT questionnaire
The questionnaire data are aggregated into the following subsections: familiarity and importance, workflow visualizations, present and emerging applications, challenges, and accuracy and resolution requirements. The results were analyzed by treating each DOT as a single entity, except where indicated. For example, there are a few instances where we received several responses from the same DOT. In these cases, the rating scale answers from the respondents within the same DOT were averaged. In multiple choice questions (for example the question asking what projects each DOT has been involved with) the answers given by multiple respondents within the same DOT were combined.
B.3.1.1 Familiarity and importance
To assess how pervasive mobile LIDAR is becoming relative to other forms of LIDAR, state DOT respondents were asked if static, mobile, or airborne LIDAR scanning had been conducted by their DOT in the last year. Unexpectedly, responses indicated that more State DOTs conducted mobile LIDAR scanning in the last year (54%) than airborne LIDAR scanning (44%), even though mobile LIDAR is the more recent technology. Additionally, 68% of state DOTs conducted static laser scanning last year and 8% of respondents were not sure which, if any, method their organization had used.
Respondent perspectives were sought regarding levels of familiarity and importance with mobile LIDAR scanning within their DOT. This series of questions was based on a 10-point scale, ranging from unfamiliar or unimportant (1) to expert or very important (10). In general, State DOT respondents tended to be more familiar with 3D laser scanning or LIDAR (mean of 6.4) compared to mobile LIDAR systems (mean of 5.4). Regardless of their current familiarity with mobile LIDAR, the DOT respondents considered these technologies to be very important to their future operations (mean of 7.8). In fact, 69% of the respondents ranked the importance of these technologies as ≥8 out of 10, with 30% defining it as “very important.” The descriptive statistics of these results are shown in Table B-2. Line graphs for these three questions appear in the top panel of Figure B-2.
Table B-2: Statistics for familiarity and importance of LIDAR among respondents
Figure B-2: Familiarity and importance of LIDAR scanning (top panel) and percentage of workflows that use or would benefit from using 3D data (bottom panel) among State DOTs.
Three-dimensional workflows are a logical extension of the collection of 3D scanning data obtained with any technology platform. To examine the current practice of State DOTs, respondents were asked to specify what percentage of technical workflows within their DOTs used 3D data. They were then asked to provide their perception of what percentage of workflows would benefit from the use of 3D data or visualization. The percentage of technical workflows within the DOTs that used 3D data or visualization varied from 0 to 100. However, as seen in Figure B-2, the data were skewed to the left, suggesting that many DOTs are currently using minimal 3D data in their workflows. When asked if 3D data or visualization would be beneficial, many respondents thought that it would be “very beneficial.”
A series of questions relating to the DOT’s published surveying and/or quality control standards were also included. First, a qualitative yes/no question was posed to determine if the DOT in question currently publishes standards. If this question was answered affirmatively, it branched into additional questions regarding the subject’s familiarity with these published standards, and if they cover the use of static or mobile LIDAR. Thirty-eight of the DOTs said that they had published surveying and/or quality control standards, and among that group of respondents the distribution of respondents was skewed to the left, indicating that personnel are generally familiar with the standards. The respondent’s familiarity with their DOT’s current surveying and/or quality control standards is presented in Figure B-3. Although most (76%) of the State DOT respondents have published standards, only 18.4% of those DOTs (7 DOTs) had standards covering the use of static laser scanning and only 10.5% (4 DOTs) had standards covering the use of mobile LIDAR/laser scanning. Figure B-4 presents a scale of DOT respondent’s familiarity with current surveying and/or quality control standards. As shown in Figure B-4, the State DOT’s that did not have published standards (white) appear to be mostly within the Midwest and East.
Figure B-5 shows the number of DOTs that have been involved with projects using airborne LIDAR, mobile LIDAR, and static laser scanning within the last 12 months. This question provides an indication of which DOTs are actively using the technology and which are currently at the investigation stage. Static laser scanning was the most common, with 34 of the 50 DOTs being involved with this service in the last 12 months. Twenty-seven DOTs used mobile LIDAR, compared to 22 who used airborne LIDAR. Only 4 respondents from individual DOTs responded that they were “Not sure.”
Figure B-3: Respondent’s familiarity of the organization’s current surveying and/or quality control standards
Figure B-4: Map of State DOT’s employee familiarity of current surveying and/or quality control standards
Figure B-5: DOT LIDAR involvement over the last 12 months
In the context of this document, workflow describes the sequence of steps that ensure quality completion of the final product or project. Varied results were found when trying to determine the proportion of work/data acquisition that was performed in-house versus contracted out to private firms, as shown in Figure B-6. Visual inspection of the data shows that slightly more work/data acquisition is performed in-house rather than contracted out to external service providers. Nearly one-third of the responses identified that between 80% and 100% of work/data acquisition was performed in-house. However, the number of “Not sure” answers (average of 20.3% of the responses), indicates a measurable portion of respondents are unclear as to the proportion of subcontracted work within their DOT.
As shown in the descriptive statistics presented in Table B-3, both surveying work/data acquisition and design work is only slightly conducted more in-house than contracted out, with average percentages of 57.9 and 53.3.
Table B-3: Statistics for percent of data acquisition and design work performed in-house vs. contracted out
Figure B-6: Percentage of surveying work/data acquisition and design work that is performed in-house versus contracted out to consultants
Additional explanatory evidence for the “Not sure” responses for both of the previous questions can be seen in the supplemental comments that were provided. The likelihood of tasks being performed in-house often times depended on the equipment owned by the DOT. California specifically mentioned that because they had ownership of Leica static lasers, scans are performed in-house; however, mobile LIDAR scanning is contracted out to consultants by Caltrans because they do not currently own a system. Other DOTs cited economic growth, for example increases in oil development in western North Dakota, as a cause of sudden increases in contracting with consultants because of critical project deadlines. Minnesota also mentioned their full time employee budget constraints as a reason to contract work out to private firms. It appears that results can vary at times for any DOT, peaking due to increased workload, in-house budget constraints, and ownership of the required equipment.
After defining the extent of subcontracted survey and design work, the next questions focused on whether 3D data and/or visualizations were included as components of current DOT workflows. Respondents were first asked if they knew the percent of the technical workflows using 3D data, followed by their perception of what percentage of workflows would benefit from the use of 3D data and/or visualization. The percentage of technical workflows within the subject’s DOT that use 3D data and/or visualization varied from 0 to 100, but as presented in Figure B-7 the data skews to the left, suggesting that many DOTs are using minimal 3D data in their workflows. However, when asked if 3D data and/or visualization would be beneficial, many respondents thought that it would be “very beneficial”.
Table B-4 shows that the data is heavily skewed to the right, with an average of 74.2% and a standard deviation of 25.3%. As indicated by previous questions, 3D data technologies as well as mobile LIDAR are perceived to be very important and beneficial to the future DOT operations.
Figure B-7 shows the percentages of current technical workflows, by State DOT, that use 3D data. Data are aggregated into groups of 20% and range from a low percentage of 3D workflow (0-20%, light gray scale) to considerable 3D workflows (80-100%, darker gray scale). The DOTs that responded “not sure” are colored in white. A visual inspection of the geographic distribution may suggest a “hot spot” for significant 3D workflows in a north-south band in the middle of the country (including North and South Dakota, Nebraska, Kansas, Oklahoma, and Louisiana.
Figure B-7: Percent of workflows using 3D data and percentages that would benefit
Table B-4: Statistics of 3D data use in DOTs
As shown in Figure B-8, most DOTs are either currently transitioning to 3D workflows (34%) or have transitioned to 3D workflows in software such as computer-aided drafting (CAD) and geographic information systems (GIS) (42%). Fourteen percent of the DOTs that responded to the questionnaire said they currently use only 2D CAD and GIS software.
Figure B-8: Geographic representation of the percentage of workflows in each DOT that use 3D data
Figures B-9 and B-10 consider responses to the question, “Where is your organization in terms of the transition from 2D to 3D?” Among the responders, 10% were not sure, 14% reported using only two-dimensional (2D) computer-aided design (CAD) and GIS software, 34% reported that they are currently transitioning to 3D workflows, and 42% have transitioned to 3D workflows in CAD and GIS software. The research team postulates that these clusters are perhaps using 2.5D (i.e., only one Z value for X and Y values) and Digital Terrain Models (DTMs) but probably are not using full 3D design models. Most of the State DOTs that indicated they are currently transitioning from 2D to 3D are located east of the Mississippi River.
Many of the respondents perceive that 3D data within their technical workflows would benefit their DOT; however, their DOT is not currently fully utilizing the technology. The respondents recognized technical expertise of the staff, funding, and organizational issues to be the greatest factor holding back the adoption of 3D workflows, with 57%, 41%, and 41% of all respondents choosing these factors respectively (Figure B-11). Other primary issues included value proposition (25%), the organization’s inertia (26%), and lack of proper software (29%). The lack of appropriate software may be influenced by several related factors such as funding or technical expertise.
The supplemental comments for the workflows provide some insight into the answers given by the respondents. Some DOTs have implemented 3D modeling workflows, but the significant learning curve of the technology and the infrequent occurrence of large projects that would immediately benefit from 3D restrict its full adoption. California, for example, mentioned that they have utilized 2D paper plans for decades, making the move to 3D products such a large shift that “many are afraid of the risks with new procedures.” The data shows that these users agree that 3D data and visualizations could benefit their DOT, but at the moment, this shift is too great and requires unavailable manpower. This sentiment was reiterated by the North Dakota DOT, who made it clear that their “largest hurdle is manpower.” Other DOTs were not sure that 3D workflows were worth the investment.
Figure B-9: Organization’s transition from 2D to 3D
Figure B-10: The State DOTs transition from 2D to 3D
Figure B-11: Factors holding back the adoption of 3D workflows
B.3.1.3 Applications (present and emerging)
A primary intent of this questionnaire was to generally identify present and emerging applications where DOTs were using mobile LIDAR data, in one form or another. In many cases, applications rely on geospatial datasets that can be derived from a variety of technologies, such as photogrammetry and/or LIDAR, without the end-user being aware of the actual acquisition source of the data. For example, features may be extracted from both a mobile LIDAR point cloud and photogrammetric data and integrated into CAD linework or GIS features. Hence, it is likely that mobile LIDAR will be useful for creating many of these derivative products needed for a variety of applications that may not yet be directly identified in this questionnaire, which may be more focused on the delivery applications rather than data use applications.
Of the 50 DOTs sampled, 25 reported having had direct experience with mobile LIDAR. Of those 25 DOTs, 80% have utilized LIDAR for engineering survey applications, which is the most common usage (Figure B-12). After engineering survey applications, the most pervasive applications were mapping (68%) and digital terrain modeling (64%). Accident investigation (8%), drainage analysis (4%), and emergency response (0%) were applications in which mobile LIDAR use was relatively rare. Other applications provided by the respondents included planning, land inventory, structural analysis, and research.
There was a significant correlation between current and emerging applications of mobile LIDAR within the DOTs. Respondents expressed the belief that the top three mobile LIDAR applications that their DOTs would pursue within the next 5 years would be the same top three applications that the DOTs have direct experience with currently. Other applications that DOT respondents frequently selected as likely to be pursued in the next 5 years included clearance surveys and pavement analysis. The DOT respondents expressed that they expect all of the applications listed in the questionnaire to be pursued in the next 5 years (Figure B-12). They indicated that applications for which mobile LIDAR use is currently rare (drainage analysis, accident investigation, and emergency response) will be pursued at reasonable participation rates (46%, 16%, and 30%, respectively). Operations and maintenance, railroad catenary work, state-wide traffic operations, pavement striping, and asset inventory were identified as other potential applications of mobile LIDAR.
Based on the specific population contacted to complete the questionnaire, it is not surprising that geomatics/surveying would be selected as the most common type of service provided by their department within the DOT or agency (82% of the DOTs confirmed this assumption). Other common services provided by subject’s unit within their DOT (Figure B-13) included engineering design (46%), asset management/inventory (40%), and research (34%).
As shown in Figure B-14, the respondents once again believe that these technologies, specifically mobile LIDAR, will be very important to the future operations of their DOT. As can be seen, the curve is heavily skewed to the right, with 62% of the respondents ranking the importance from 8 to 10 out of a 10-point scale.
Figure B-12: Mobile LIDAR applications that organizations will pursue in the next 5 years
Figure B-13: Types of services the organizations provide
Figure B-14: Importance of mobile LIDAR over the next 5 years
B.3.1.4 Challenges and need for guidelines
One of the most valuable contributions of the state-of-the-practice reviews is the compilation and dissemination of challenges faced by State DOTs regarding the adoption of 3D workflows and the implementation of mobile LIDAR scanning. State DOT and service provider responders were asked to identify the three most significant issues preventing the adoption of 3D workflows by DOTs (Figure B-15). When multiple subjects were included from a single DOT, all selections were aggregated into a single response for that DOT. Approximately half of the DOT respondents selected the dataset size/ complexity and the cost as the most significant challenges. Other frequently selected challenges included technical expertise (57%), and organizational challenges (41%).
Given the results regarding current data and software limitations in laser scanning, it was important to understand how DOTs are using and sharing data within their divisions. The response results were similar, with 54% of the organizations responding that they manage data separately within each individual department and 46% responding that the data is centrally managed and updated by each department. However, in three instances, two respondents in the same organization had different responses to how data was managed. These conflicting responses were omitted from the results.
To provide additional background information, the respondents were asked to identify those areas where the proposed guidelines would be most helpful to their organization. The results are presented in Figure B-16. Many DOTs selected all options available including survey accuracy (78%), quality assurance and quality control procedures (80%), data interoperability (70%), data management (76%), and software integration (72%). The data suggest that the DOTs and the other agencies questioned would find proposed guidelines regarding the use of mobile LIDAR to be essential to future operations and projects.
The DOT respondents indicated that guidelines were needed to help enable further adoption of the technology. The guidelines will also need to be flexible to address the varying needs of end users for a variety of applications. The DOTs mentioned several strategies to streamline adoption of scanning technology, including:
- Convince “non-design users to accept this tool as viable”.
- Work with asset management and GIS professionals, who have been hesitant to accept this technology. (However, one DOT mentioned that their organization uses the technology for asset management but not for engineering/design work.)
- Create a professional network, through which information and procedures could be shared.
Produce flexible guidelines to address the varying needs of end users for their many applications.
Figure B-15: Mobile LIDAR surveying challenges experienced by DOTs
Figure B-16: Areas were guidelines would be most helpful
B.3.1.5 Accuracy and resolution requirements
Two of the most important factors involving geospatial data are accuracy and resolution. The respondents were asked to identify the level of accuracy and resolution that was required to support the department’s daily workflow. The largest request occurred at the centimeter level (71% of department responses for accuracy and 57% for resolution) as presented in Figure B-17.
Figure B-17: Level of accuracy and resolution required to support daily workflows
B.3.2 Additional transportation agencies
Of the 74 responses to the DOT questionnaire, six were from transportation agencies that were not State DOTs. The six agencies included Alberta Transportation, TranSystems, Central Federal Lands Highway Division, Federal Highway Administration, Mainroads of Western Australia, and the Department of Rural Roads. The data provided by these agencies were analyzed separately; however, the relatively small sample size limits the statistical comparisons that can be made with the 50 State DOTs. Many of the following comparisons are aggregated into the same groups (familiarity, work-flows, direct experience, and the accuracy and resolution) from the DOT questionnaire section.
Respondents from the non-DOT agencies had a similar familiarity with LIDAR, with means of 7.2 for non-DOT agencies and 6.4 for State DOTs. Based on the small population, non-DOT agencies seemed to be more familiar with mobile LIDAR than State DOTs (mean of 6.8 vs. 5.4, respectively). However, both groups valued these technologies as very important to future operations, with means of 8.5 (non-DOTs) and 7.8 (DOTs).
Of the six agencies, three responded that the organization currently had published surveying and/or quality control standards. Comparisons between these groups were not conducted due to the small sample size. Comparisons between the percentages of surveying work and design work performed in-house versus contracted out were also not conducted due to the small comparison sizes. This was the case for all rank scale questions.
The top three applications that the non-DOT agencies have had direct experience with were the same applications selected by the DOTs: engineering survey, mapping, and digital terrain modeling. These three applications were also the most selected applications to be pursued in the next 5 years by both groups. With regards to the transition from 2D to 3D workflows, non-DOT agencies reported that they are primarily in the transitioning stage (67% of non-DOTs vs. 34% of DOTs).
With regards to the transition from 2D to 3D workflows, the non-DOTs agencies are primarily in the transitioning stage with 67% compared to the 34% with DOT’s.
For both groups, respondents considered mobile LIDAR to become important within their organizations with a mean rank of 7.6 for DOTs and 8.3 for other transportation agencies, with the rank 10 being the most important.
Top challenges for the non- State DOT transportation agencies included software interoperability/ data exchange (also a top challenge for State DOTs) and dataset size/ complexity. Compared to the State DOTs, non-DOT agencies considered data management guidelines to be less helpful (33% for non-DOTs vs. 76% for DOTs vs. 86% for service providers), whereas guidelines on survey accuracy were indicated to be more beneficial (83% vs. 78% vs. 43%).
Although the number of other transportation agencies is too small for a full comparison, it appears that the accuracy and resolution supported by the responding departments daily workflows were very similar to those of the State DOT respondents, requiring centimeter level accuracy. However, the management of data was different between the two groups, with five out of the six non-DOT agencies managing the data centrally and updated by each department. For State DOTs, 53.7% of the respondents said that data was managed separately within each department, compared to 16.7% for non-DOT agencies.
B.3.3 Service provider questionnaire
The Service Provider Questionnaire was created and distributed to mobile LIDAR service providers to obtain further insight concerning the current challenges in providing mobile LIDAR services and the need for performance-based guidelines. Given both the relatively small sample size as well as the desire to provide each service provider with the opportunity to discuss issues that may not be specifically covered in the questionnaire, the respondents were interviewed via telephone. In total, 14 industry leaders were interviewed, and the results are summarized in the following section.
B.3.3.1 Familiarity and importance
The service providers were initially asked how long (in years) their company has been involved with 3D laser scanning and/or static LIDAR. They were then asked about their experience with mobile LIDAR. The descriptive statistics in Table B-5 show that service providers participating in the questionnaire have been involved with static LIDAR for an average of 8.9 years (with a median of 9.3 years) while their individual involvement with mobile LIDAR has been more recent, with an average of 4.2 years and a median of 3.0 years. This indicates that most of these companies interviewed have been early adopters of scanning technology and are among the most experienced in the market.
The responding service providers indicated that LIDAR technologies will become very important to future DOT survey operations (Figure B-18), with 92.9% of the service provider responses ranking the importance at or above 8 on a ranking scale of 1 to 10. Furthermore, 42.9% selected the highest rank (10) of importance possible.
Table B-5: Years of involvement with static and mobile LIDAR/laser scanning systems
Figure B-18: Future importance of LIDAR-based technology
An initial series of questions regarding workflows using mobile LIDAR were asked (Figure B-19). The service providers interviewed indicated that a majority of their company’s mobile LIDAR-related business involves a DOT. More specifically, across all 14 service providers, a mean of 55% of the work that they perform and a median of 60% (standard deviation of 21%) is completed for a DOT. The results also show that 79% of all the DOTs that the service providers are currently working with are at least investigating the use of mobile LIDAR. The number of DOTs that are currently working with mobile LIDAR averaged 48%. The service providers, on average, also predicted that 81% of the DOTs would be using mobile LIDAR within the next 5 years.
In contrast to the DOTs, many service providers felt that DOTs were far from a transition to 3D workflows. In most cases, service providers stated that they are delivering 2D or 2.5D CAD or DTM models to DOTs, rather than 3D point cloud models. Many of these are delivered as traditional plan and profile products. These data reveal an important disconnect between the people responsible for acquiring 3D LIDAR data and those responsible for using the data in the design workflows.
Figure B-19: Mobile LIDAR related business involving DOTs
When questioned regarding the use of 3D data by DOTs, the service providers reported, on average, that 80% of the DOTs were only using 2D/2.5D CAD and GIS software, 18.5% were transitioning to 3D model based workflows, and 27.5% had already transitioned. However, it should be noted that three respondents were “not sure”, and five respondents stated that none of the DOTs have transitioned to 3D model-based workflows.
The service providers were asked to identify the top three issues holding back the adoption of 3D model-based workflows within DOT (Figure B-20). Technical expertise and organizational issues were selected as the top two issues with 79% and 71%, respectively. The third most common response to this question, with a percentage of 36, was a tie between software, and “other”, which included concerns with management and workforce adaptation.
Regarding implementation challenges of mobile LIDAR scanning by State DOTs, service provider and State DOT responders showed some consistencies. Service providers identified technical expertise (57%), value proposition (29%), lack of standards (29%), and the size and complexity of datasets (29%) (Figure B-21). “Other” challenges included reluctance to accept the new technology, concerns with replacing tried and tested mapping methodologies and training, and a rigid procurement policy. Additionally, value proposition and inertia were each identified by 29% of service provider responders.
Figure B-20: Top three issues reported by service providers as holding back the adoption of 3D workflows in DOTs
Figure B-21: Top three factors delaying the adoption of mobile LIDAR by the DOTs
Regarding integration of mobile LIDAR with airborne or static GPS data, the service providers agreed that the process is generally straightforward, provided appropriate geo-referencing had been completed. One service provider mentioned that there can be some challenges with integration when combining lower accuracy data (e.g. inventory) with high accuracy data (e.g. engineering survey). In such cases, they felt that the dataset should be provided with a disclaimer. Several service providers mentioned that they have little experience with integrating airborne LIDAR data with mobile LIDAR data, but have integrated a substantial amount of static data with mobile to provide additional detail in areas where they could not get mobile LIDAR access. One respondent mentioned that most highway projects require the integration of multiple types of survey equipment (e.g., LIDAR, total station, etc.) to complete the necessary survey work for a project. Another respondent felt that in the future, the professional mapping firm would determine the appropriate tool for obtaining the best data rather than the DOT specifying the actual tool to collect the data.
The service providers were also asked how they perceived data was shared and managed within DOTs. The service providers responded that 69% of the DOTs manage data separately within each individual department and 31% of the DOTs manage data centrally and updated by each department.
B.3.3.3 Applications (present and emerging)
Although the responding service providers currently support many of the applications they were asked about, service providers indicated that they anticipate supporting significantly more applications within the next five years, as shown in Figure B-22. Currently, most mobile LIDAR projects involve: engineering surveys, mapping, and DTM, with 100% of the service providers providing each of those applications. Applications that the service providers have been least involved with include: accident investigation (14%), slope stability/landslides analysis (43%), urban modeling/GIS (50%), and emergency response (50%).
Figure B-22: Supported applications by service providers currently and in the future
B.3.3.4 Challenges and need for guidelines
The service provider companies were asked to identify those areas where the proposed guidelines would assist their company in the procurement of mobile LIDAR/laser scanning products and/or services. QA/QC procedures (86%), survey accuracy (64%), and data interoperability (57%) are the areas that were most often identified (Figure B-23). It was also mentioned that the purpose for acquiring the data, a checklist of possible data uses, lineage and traceability, and asset metadata were also important areas for guidance.
Figure B-23: Areas in which guidelines would be most helpful regarding the procurement of mobile LIDAR/laser scanning products and/or services
The service providers were asked about their familiarity with DOT published specifications. Eleven of the 14 service providers responded that most DOTs have published surveying or quality control procedures. However, when asked whether most state DOTs that have surveying standards covering static laser scanning, only three service providers responded affirmatively. Similarly, service providers confirmed that most DOTs do not have mobile LIDAR standards. State DOTs identified with static LIDAR/laser scanning specifications include California, North Carolina, Michigan, Washington, and Texas. Caltrans and MoDOT were the only two DOTs identified as having specifications in place for mobile LIDAR. However, it was also mentioned that TexDOT was currently developing specifications. Michigan and New York were also identified as possibly having specifications, but the respondent was not sure.
Regarding the development of national standards, two service provider respondents felt that each DOT should develop their own static or mobile LIDAR standards, whereas 11 service provider respondents felt that a single standard should be adopted by all DOTs. One service provider did not respond. Comments from service provider respondents to this question included the following:
- Best practices or guidelines would be preferred over rigid standards. Standards may stifle innovation and can be confining. Flexibility is needed for projects and technology.
- Standards could be like licensure requirements, in which there is a national standard with state supplements. New standards should be integrated into existing DOT standards.
- Existing photogrammetry and survey standards could be adopted.
- Standards should focus on deliverables, not methodology.
- Levels of detail include engineering survey, mapping, and asset grades
When asked if performance-based specifications would be appropriate to use for mobile LIDAR, six respondents agreed they would be helpful. However, some of those provided the condition that “adequate QA/QC provisions are in place” and there is an “atmosphere of trust” between the agencies. The remaining respondents were not sure or did not respond to this question.
When asked what DOTs could do to streamline the adoption of mobile LIDAR, the responses from service providers included the following:
- Exchange knowledge between DOTs.
- Build from experience with airborne photogrammetry.
- Hire an expert consultant.
- Focus on deliverables/ end products rather than data acquisition.
- Develop standards or adopt guidelines. Use the recently developed Caltrans specifications.
- Adopt standards and develop good quality, clear Requests for Qualifications (RFQs), to avoid being disappointed with the results.
- Be willing to experiment.
- Understand how mobile LIDAR can be used for multiple projects rather than narrowly defining it by project. Learn how the data may be used by multiple divisions within an organization.
- The determination of cost recovery in contracts must allow for new technology.
- Calculate cost savings from mobile LIDAR.
- Realize the safety benefits of mobile LIDAR.
- Realize the changes in workflow from field to office.
Similarly, the service providers were asked what DOTs can do to streamline the procurement process for mobile LIDAR, which has been a challenge for many DOTs. Responses included:
- Exchange knowledge between DOTs.
- Have a clear scope of the work, consistent with standards.
- Focus on deliverables, not data collection.
- Understand that most of the work for scanning is done in the office, not in the field.
- Use qualification-based criteria (e.g., pilot projects for demonstration) rather than lowest bid.
- Implement more prequalified Indefinite Delivery Indefinite Quantity (IDIQ) projects.
- Relax procurement guidelines that are locked into old procedures.
- Establish new rates for mobile LIDAR services.
- Allow requests for proposals (RFPs) to be accepted between states across state lines
B.3.3.5 Accuracy and resolution requirements
Service providers were asked to provide the level of accuracy that their company would specify as being required for specific applications, such as engineering survey and pavement management (Table B-6). Some of the greatest accuracy discrepancies were reported for asset inventory and sign inventory, with a range of 90 to 56 cm respectively. Table B-7 shows the best horizontal and vertical accuracy (in cm) that the service providers specified as achievable with mobile LIDAR. The results from the responding service providers were transcribed into ranges, from the smallest accuracy required to the largest. The service providers provided responses in both SI and US customary units; however, all values were converted to SI units for ease of comparison.
Table B-6: Range of accuracies that the service providers specify as being required
Table B-7: Horizontal and Vertical accuracies stated as achievable by service providers
The service providers were also asked what order of survey control was needed to achieve the desired accuracy. Three service providers said that the control varied and was condition-dependent, whereas one service provider said that no control was needed. Two service providers mentioned that under good GPS conditions, ground control points should be every 200 m (approximately 660 ft). One of these service providers also indicated that under poor GPS conditions, control points should be set every 100 m. A few service providers discussed the quality rating of the survey control used. One service provider stated that he/she only used first-order control; another stated that second-order control was acceptable; and a third stated that “high” order control was needed. Two service providers said that the recent Caltrans (2011) mobile LIDAR specifications govern the survey control they use.
B.3.3.6 Deliverables, and reporting
Most service providers agreed that the type of deliverable varies depending on the needs of the particular project and DOT. Potential deliverables identified by the service providers included the following:
- Point clouds (raw, geo-referenced, or classified LAS file)
- Viewing software
- Calibrated imagery
- Reports (methods, procedures, data quality achieved, control fit)
- CAD or geodatabase files of extracted features
- Control surveys
- Lineage documents
- Corrected trajectory files
- Check points
Some service providers expressed the belief that DOTs own the data from the mobile LIDAR services they pay for; however, some were concerned that the DOTs would be unable to use the full datasets. It was also mentioned that data ownership should be determined as part of the contract. It was also mentioned that data ownership should be included as part of the contract.
In addition to accuracy certification, many service providers agreed that reporting on the survey methodology was an important part of the project deliverables. Many mentioned that this information was critical to ensure that the results could be reproduced. However, three of the 14 service providers indicated that they should only be required to certify the final accuracy. These service providers felt that reporting the methodology would reveal proprietary information in some cases.
The DOT and service provider questionnaires provided valuable insights into the current and future plans of DOTs for the use of mobile LIDAR. These questionnaires established a technology adoption baseline that can be used to measure future progress. The DOT questionnaire included responses from all 50 State DOTs in the U.S., plus a few other transportation agencies. The service provider questionnaire included results from 14 highly experienced mobile LIDAR service providers.
Many personnel within the DOTs appear to be very interested in the use of scanning technology and feel that it will become a critical part of their operations in the next 5 years. The DOTs identified several applications for which they currently use mobile LIDAR and stated that they foresee expanding the use of the technology into numerous transportation applications over the next 5 years. The level of expertise related to mobile LIDAR among the DOTs showed substantial variability, particularly as compared to static scanning. Interestingly, more DOTs have used mobile than airborne LIDAR within the last year, even though mobile LIDAR technologies are comparatively less established.
Responders cited many challenges, both organizational and technical, that must be addressed before the DOTs can optimize the use of mobile LIDAR and completely integrate it into their workflows. One of the most significant challenges identified regarding the adoption of mobile LIDAR by DOTs was cost. This finding indicates that the respondents are not clear where savings come from and what the return on investment is from mobile LIDAR. Additional education and evidence may be required to overcome this hurdle.
Comparison of the DOT and service provider questionnaire results highlighted key differences between the perceptions of DOTs and service providers on the utility of 3D data. Most significantly, many service providers felt that DOTs were far from a transition to 3D workflows. However, most DOTs stated that they had transitioned or were well into the process of transitioning. These data reveal an important disconnect between the people responsible for acquiring LIDAR data and those responsible for the design workflows. Further, there are discrepancies between respondents as to what 3D is. As mobile LIDAR usage expands, it becomes increasingly important for both DOTs and service providers to understand how 3D data can be integrated into DOT workflows. All responders agreed that there are many challenges to overcome for a complete transition to 3D within DOTs.
The insights provided by this questionnaire form a framework to understand the key issues currently faced by Most DOTs believe very strongly that survey accuracy, QA/QC procedures, data interoperability, data management, and software integration are the most important topics to be addressed in the proposed guidelines, with nearly equal emphasis on each topic. Somewhat in contrast, the service providers believe that QA/QC procedures alone were by far the most important issue to address with the guidelines.
These insights were incorporated in the development of these national guidelines, which will assist transportation personnel in utilizing mobile LIDAR effectively for a variety of applications.
Click Here to view pdf versions of the questionnaires used for this report.