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GIS Inspection using GPS and Digital Camera
Andy C. Shaw
CADDScan Engineering, Inc.
9861 Broken Land Parkway, Suite 168 Columbia, MD 21046
An integrated project solution
Andy C. Shaw
CADDScan Engineering, Inc.
9861 Broken Land Parkway, Suite 168 Columbia, MD 21046
An integrated project solution
Goal
The goal of this paper is to share the methodology and experience CADDScan developed for a utility inspection project. Due to traffic and manhole water constraints, an automated underground manhole inspection approach was developed to quickly collect and record the field data. The inspection process utilized a Trimble GPS system, Trimble Data Dictionary, Digital Camera, Differential Correction, MicroStation CADD program, Micro Station Development Language (MDL), ESRI Arc/Info, and ESRI MapObjects development tools.
Introduction
CADDScan was a contractor to Bell Atlantic Network Integration (BANI), providing utility inspection and verification services for the City of Baltimore’s 800Mhz Radio Implementation Project. One of CADDScan’s primary responsibilities was to identify existing conduit holes available for the fiber optic cable connectivity. There are approximately 800 manholes within the project area. Each manhole must be quickly surveyed and inspected - because many of them reside in high traffic density area and are water filled. In order to minimize the time required to locate the manhole coordinates and collect the necessary project data, Trimble GPS with pre-defined input interface was developed for convenient field data input. At the beginning of the project, a camcorder was used to record the condition inside the manhole. Later into the project, the project team discovered that it was rather difficult to identify where in a tape the information for a specific manhole is located. A Kodak digital camera was then selected to replace the camcorder and was found to be time-efficient and easy to use.
After the fieldwork was completed, the GPS field data was downloaded to an office computer for further processing. The Trimble Pathfinder program was used to perform coordinate projection, GPS post differential correction, and data export to Arc/Info file format. The Arc/Info file was also converted to Micro Station format with attribute pointer reserved as a part of the Micro Station element data. The reason for this conversion was to enable database attribute review and verification, while creating design drawings within Micro Station environment. The Arc/Info to MicroStation conversion can be accomplished using an AML program from the Arc/Info environment. CADDScan also has a utility to read Trimble-generated MicroStation files, reserving database linkages.
A user interface was developed using MicroStation Development Language (MDL), which enables attribute accessing from within MicroStation. The photo image names were entered as attributes in a separated database table pointing back with the corresponding manhole. Users can click on a manhole to display the photo images to verify the selection of the conduit slots is acceptable.
Since Arc/Info was the required GIS deliverable format, CADDScan also developed an ESRI MapObjects-based graphic user interface to allow the project staff to access the manhole data directly from a Microsofl Windows environment.
The manhole inspection work was completed in approximately three months. GPS utilization significantly reduced the required time for locating manhole coordinates. Without using the camcorder and the digital camera, it would have been impossible to go back to the water filled manhole for design verification. MicroStation successfully produced the construction drawings and the as-built documentation. Manhole GIS data sets are maintained as a reference for future overlays in Arc/Info format. Since a digital camera was not used until later in the project, most of the manhole photos were taken by a camcorder. At this time, the project team does not maintain a complete photo set for all the manholes that were inspected.
Solution Components
Trimble GPS PathFinder
The Trimble ProXL GPS was used to collect the coordinates of the manhole. A data dictionary with pre-defined pick-lists, allowing convenient attribute selection was developed for data input. A serial connection cable was used to download data from the GPS memory card to the computer at the beginning of the project. Towards the end of the project, Trimble ASPEN application was used to allow the operator to directly input field data into a portable computer. ASPEN data transferring was much more efficient than the serial data connectivity, and will be used for all future projects.
Coordinates Projection
The project requires the delivery of Arc/Info data using a Baltimore Grid coordinate system. The Baltimore Grid uses the Baltimore Monument as the (0,0) central point. The City provided control points for data projection. An Arc/Info AML was created to convert State Plane coordinates based GPS data to the Baltimore Grid.
Post Differential Correction
The field data collected with the Trimble ProXL GPS needs to be corrected for positional accuracy. The Department of Defense currently broadcasts signals from the satellites with small random spikes in the signals. These spikes need to be identified and corrected. To accomplish this, the GPS Base station data from locations within Maryland or surrounding areas must be used to correct the field collected GPS data positions. This base station data is collected over a known reference point, sorted by date and time. This data is published on the Internet and is easily downloaded. Then using routines supplied by Trimble, the DXF files of the GPS collected data can be corrected within 3 meters. If greater accuracy is required, a base station can be set up within a few miles of the project and then sub-meter accuracy can be accomplished.
Data Conversion
After the fieldwork is processed for positional accuracy, the Trimble Pathfinder program data is exported to an Arc/Info file format. The Arc/Info file is also converted to a MicroStation format with attribute pointer reserved as a part of the MicroStation element data. The reason for this conversion is to enable database attribute review and verification while creating design drawings within Micro Station environment. The Arc/Info to Micro Station conversion can be accomplished using an AML program from Arc/Info environment. CADDScan also created a utility to read Trimble-generated MicroStation files reserving database linkages.
Bentley MicroStation and MDL Application
The attributes of MicroStation elements are also desired because the engineering drawings for this project were created using Bentley Micro Station. Frequently, a designer has the need to review field attributes and the images of a manhole to make the best conduit slot selection. In order to satisfy these requirements, an MDL based GUI is developed for displaying manhole attributes and attached images. For each manhole, a unique identifier is assigned for the project. In a separated database table, all the image file names are stored with their corresponding manhole identifier. When a user clicks on a manhole querying for the images, the MDL program reads the image table and provides the option to open each of the associated images.
Kodak 120 Digital Camera
The Kodak 120 digital camera proved to be an excellent tool for capturing field images, especially when compared to a camcorder. This digital camera is easier to operate and carry. The built-in flash is sufficient for taking photographs within the manholes. Using a compressed mode, a 100+ high-resolution photo can be taken and stored in the camera’s memory card. The transferring of photo images is extremely easy, because Kodak supports PCMCIA interfacing, in which a user can view and read photo images as if the digital camera memory card is a hard drive of the computer.
ESRI Arc/Info Program
The required project deliverables are in ESRI Arc/Info formats. After the design is completed and the attributes are compiled, the MicroStation files are converted to an Arc/Info coverage file, again, using an AML utility. For QC viewing purpose, CADDScan internally used a MapObjects based viewing application to review and examine and attributes and images. The ability to use an independent Windows based application was proved to be desired as well as effective for this project.
Conclusion
This project demonstrated a successful integrated solution using common and practical tools. Our project finding can be summarized as follows:
The goal of this paper is to share the methodology and experience CADDScan developed for a utility inspection project. Due to traffic and manhole water constraints, an automated underground manhole inspection approach was developed to quickly collect and record the field data. The inspection process utilized a Trimble GPS system, Trimble Data Dictionary, Digital Camera, Differential Correction, MicroStation CADD program, Micro Station Development Language (MDL), ESRI Arc/Info, and ESRI MapObjects development tools.
Introduction
CADDScan was a contractor to Bell Atlantic Network Integration (BANI), providing utility inspection and verification services for the City of Baltimore’s 800Mhz Radio Implementation Project. One of CADDScan’s primary responsibilities was to identify existing conduit holes available for the fiber optic cable connectivity. There are approximately 800 manholes within the project area. Each manhole must be quickly surveyed and inspected - because many of them reside in high traffic density area and are water filled. In order to minimize the time required to locate the manhole coordinates and collect the necessary project data, Trimble GPS with pre-defined input interface was developed for convenient field data input. At the beginning of the project, a camcorder was used to record the condition inside the manhole. Later into the project, the project team discovered that it was rather difficult to identify where in a tape the information for a specific manhole is located. A Kodak digital camera was then selected to replace the camcorder and was found to be time-efficient and easy to use.
After the fieldwork was completed, the GPS field data was downloaded to an office computer for further processing. The Trimble Pathfinder program was used to perform coordinate projection, GPS post differential correction, and data export to Arc/Info file format. The Arc/Info file was also converted to Micro Station format with attribute pointer reserved as a part of the Micro Station element data. The reason for this conversion was to enable database attribute review and verification, while creating design drawings within Micro Station environment. The Arc/Info to MicroStation conversion can be accomplished using an AML program from the Arc/Info environment. CADDScan also has a utility to read Trimble-generated MicroStation files, reserving database linkages.
A user interface was developed using MicroStation Development Language (MDL), which enables attribute accessing from within MicroStation. The photo image names were entered as attributes in a separated database table pointing back with the corresponding manhole. Users can click on a manhole to display the photo images to verify the selection of the conduit slots is acceptable.
Since Arc/Info was the required GIS deliverable format, CADDScan also developed an ESRI MapObjects-based graphic user interface to allow the project staff to access the manhole data directly from a Microsofl Windows environment.
The manhole inspection work was completed in approximately three months. GPS utilization significantly reduced the required time for locating manhole coordinates. Without using the camcorder and the digital camera, it would have been impossible to go back to the water filled manhole for design verification. MicroStation successfully produced the construction drawings and the as-built documentation. Manhole GIS data sets are maintained as a reference for future overlays in Arc/Info format. Since a digital camera was not used until later in the project, most of the manhole photos were taken by a camcorder. At this time, the project team does not maintain a complete photo set for all the manholes that were inspected.
Solution Components
Trimble GPS PathFinder
The Trimble ProXL GPS was used to collect the coordinates of the manhole. A data dictionary with pre-defined pick-lists, allowing convenient attribute selection was developed for data input. A serial connection cable was used to download data from the GPS memory card to the computer at the beginning of the project. Towards the end of the project, Trimble ASPEN application was used to allow the operator to directly input field data into a portable computer. ASPEN data transferring was much more efficient than the serial data connectivity, and will be used for all future projects.
Coordinates Projection
The project requires the delivery of Arc/Info data using a Baltimore Grid coordinate system. The Baltimore Grid uses the Baltimore Monument as the (0,0) central point. The City provided control points for data projection. An Arc/Info AML was created to convert State Plane coordinates based GPS data to the Baltimore Grid.
Post Differential Correction
The field data collected with the Trimble ProXL GPS needs to be corrected for positional accuracy. The Department of Defense currently broadcasts signals from the satellites with small random spikes in the signals. These spikes need to be identified and corrected. To accomplish this, the GPS Base station data from locations within Maryland or surrounding areas must be used to correct the field collected GPS data positions. This base station data is collected over a known reference point, sorted by date and time. This data is published on the Internet and is easily downloaded. Then using routines supplied by Trimble, the DXF files of the GPS collected data can be corrected within 3 meters. If greater accuracy is required, a base station can be set up within a few miles of the project and then sub-meter accuracy can be accomplished.
Data Conversion
After the fieldwork is processed for positional accuracy, the Trimble Pathfinder program data is exported to an Arc/Info file format. The Arc/Info file is also converted to a MicroStation format with attribute pointer reserved as a part of the MicroStation element data. The reason for this conversion is to enable database attribute review and verification while creating design drawings within Micro Station environment. The Arc/Info to Micro Station conversion can be accomplished using an AML program from Arc/Info environment. CADDScan also created a utility to read Trimble-generated MicroStation files reserving database linkages.
Bentley MicroStation and MDL Application
The attributes of MicroStation elements are also desired because the engineering drawings for this project were created using Bentley Micro Station. Frequently, a designer has the need to review field attributes and the images of a manhole to make the best conduit slot selection. In order to satisfy these requirements, an MDL based GUI is developed for displaying manhole attributes and attached images. For each manhole, a unique identifier is assigned for the project. In a separated database table, all the image file names are stored with their corresponding manhole identifier. When a user clicks on a manhole querying for the images, the MDL program reads the image table and provides the option to open each of the associated images.
Kodak 120 Digital Camera
The Kodak 120 digital camera proved to be an excellent tool for capturing field images, especially when compared to a camcorder. This digital camera is easier to operate and carry. The built-in flash is sufficient for taking photographs within the manholes. Using a compressed mode, a 100+ high-resolution photo can be taken and stored in the camera’s memory card. The transferring of photo images is extremely easy, because Kodak supports PCMCIA interfacing, in which a user can view and read photo images as if the digital camera memory card is a hard drive of the computer.
ESRI Arc/Info Program
The required project deliverables are in ESRI Arc/Info formats. After the design is completed and the attributes are compiled, the MicroStation files are converted to an Arc/Info coverage file, again, using an AML utility. For QC viewing purpose, CADDScan internally used a MapObjects based viewing application to review and examine and attributes and images. The ability to use an independent Windows based application was proved to be desired as well as effective for this project.
Conclusion
This project demonstrated a successful integrated solution using common and practical tools. Our project finding can be summarized as follows:
- The use of Trimble GPS and Data Dictionary significantly reduced the effort of survey and field data collection.
- The Kodak digital camera was proved to be an effective tool for field photo taking.
- CADD design and database interfacing within Micro Station allowed the designers to viewing attributes and images while performing design.
- ESRI’S conversion utility between Micro Station and Arc/Info successfidly converted MicroStation attributes to Arc/Info.
- Windows MapObjects application appeared to be highly desirable and productive.