New emerging technologies often take their respective markets by surprise. A web search for "mobile mapping data collection guidelines" yields only one document that specifically targets this subject. Users and manufacturers are in the process of introducing a better way to collect data. As a result, the formulation of mobile mapping data collection guidelines is just starting. The development of such documents must be an ongoing process that will eventually shape widely acceptable industry parameters and practices.
Guidelines vs. Standards vs. Best Practices
We use these terms nearly every day, but do we really understand the implications of each one? Let’s take a look at their definitions from Wikipedia:
Guideline: "A statement by which to determine a course of action. A guideline aims to streamline particular processes according to a set routine or sound practice. By definition, following a guideline is never mandatory. Guidelines are not binding and are not enforced." (Wikipedia)
Best practices: "Generally-accepted, informally-standardized techniques, methods or processes that have proven themselves over time to accomplish given tasks. Often based upon common sense, these practices are commonly used where no specific formal methodology is in place or the existing methodology does not sufficiently address the issue. The idea is that with proper processes, checks and testing, a desired outcome can be delivered more effectively with fewer problems and unforeseen complications."
Guidelines and Best Practices can develop into "standards" when they are adopted as a requirement for a contract or incorporated in a governing agency’s general specifications. They can be expanded and/or modified to suit specific projects and conditions.
The mobile mapping industry is at the "guideline" stage. The technology is so new and complex that few efforts have been made to define the operation, processes and products. Educating data consumers is an essential step in the process.
Should we create them?
The purpose of a "guideline" is to create a generic description of the equipment, methods and means to achieve a specific result. The document should be in a form that can be widely accepted and understood by the consumer and the provider / supplier. A guideline should serve as the basis for a mutual understanding of outcome expectations vs. actual results.
Why do we need them?
The primary reason is business oriented. Collecting mobile mapping data is often a transaction between a data consumer and a service provider. After reviewing hundreds of RFP’s for a wide variety of services (urban planning, professional services, handheld GNSS data collection, etc.) there is frequently a severe disconnect between the consumer’s understanding of what he actually needs and what the service provider can deliver. Many times, the service provider ends up rewriting the RFP to remove unrealistic requirements or suggest better methodology. A published guideline that can be referenced by both parties would bridge the gap in understanding and foster a meeting of the minds.
Creating Mobile Mapping Guidelines
A couple of issues arise in creating any type of "standardized" guidelines for mobile mapping. Mobile mapping systems are a fusion of multiple technologies for vehicle positioning (GNSS, IMU, Odometry) and data capture (laser scanners, digital cameras). Each of these components has particular technical attributes and considerations.
The second issue is applications. Mobile mapping is being used for an increasingly number of diverse projects: GIS asset management, transportation planning, utility route surveys, construction as-builts, earthwork volume calculations, and urban 3D modeling – to name just a few. Specific requirements for each of these applications can vary greatly.
Here is a basic framework with a few comments for the creation of detailed guidelines:
- An overview of the equipment, technology, operational parameters, and procedures that will be used to produce specific deliverables
- Route Planning – a driving plan that will efficiently encompass the target area
- GNSS Mission Planning – analysis of dates and time periods for optimal GNSS reception
- Control – Accuracy requirements and location intervals for setting local control points
- GNSS Base Stations – distance from project, site considerations, logging rates
- Calibration – if required for proper system operation
- Vehicle – limitations on road speed, overlap requirements
- Image Capture – camera view angles, capture rate
- LiDAR – Range, point density, relative and absolute point accuracy
- Data – storage, backups, transmission
- GNSS Post-processing
- Control Point Registration – adjustment of trajectory, point cloud, and images to local control
- Vertical Adjustment – geoid or vertical datum specification
- Quality Control
- GNSS Quality – actual PDOP and RMS achieved
- Point Accuracy Assessment – comparison to local known data
- Point Cloud – requirements for file format, tiling, noise reduction, coordinate system
- Geo-referenced images – resolution, format
- Dataset – delivery method
Recently, the Transportation Research Board released a contract for the development of "Guidelines for the Use of Mobile LiDAR in Transportation Applications". This project is specific to DOT applications. It is intended to produce a document that can be widely accepted and implemented , avoiding duplicate efforts by the multiple states. It will be very interesting to how the results of this award will contribute to the general mobile mapping industry. An overview of the contract can be found at: http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=2972.
Another major effort to create a Best Practices document is underway by the ASPRS Mobile Mapping Systems Committee. Their goal is to create an initial draft by the organization’s annual meeting in March 2012. Readers can contact Craig Glennie, Committee Chairman at clglenni@Central.UH.EDU for more information.