Ask The Inspector...
I have used other LiDAR providers. Why is your service better? Aren't these products all the same? Why are your costs lower?
The difference is that we are not simply a LiDAR provider – GeoDigital International provides solutions. GeoDigital's LiDAR clients span 11 countries with projects totaling more than 27,000 miles of transmission corridor survey for the purpose of line up ratings, new line construction, sag analysis. The breadth and depth of our experience has allowed us to develop services and proprietary software that offer our customers more "bang for the buck" ... pure and simple.
Why is your methodology using LiDAR better than the traditional ground survey?
A properly planned and executed LiDAR survey produces accurate results in less time and in greater detail than traditional ground survey methods. That means lower costs to our customers. The short answer is you see everything within the swath width of the laser scan ... trees, conductor, structures, access roads, encroachments, fence lines, etc. All points within the scan have an X, Y, and Z position, allowing you to see your world in 3D by using LiDAR data to help you make informed decisions and make your work easier.
What is the difference between your methodology using LiDAR and conventional photogrammetry?
LiDAR surveys are fast, accurate, and cost effective. LiDAR data provides 3D data at the rate of 30 – 60 mph along transmission corridors. Even though LiDAR requires post processing to produce a deliverable product, it is far superior to the 2D to 3D transformation necessary in photogrammetry. As the data is less impacted by vegetation that can block a clear view of the lines, LiDAR produces far more accurate and detailed results.
Can LiDAR data be integrated with previously collected Asset Mapping data?
YES. Since LiDAR data is truly an actual 3D representation of all assets, it can be integrated with previously collected data sets. LiDAR will make your current data sets more accurate while adding a third dimension.
What about attribute detail? Will I be able to determine the pole type, structure, cross arm configuration, conductor bundles, etc.? Some attribute details can be determined using LiDAR data combined with the simultaneously collected color images. Depending upon the required altitude of the survey, the images can produce resolutions to less than 3 inches. For conductor bundles, the laser data will show individual lines and, therefore, the bundling.
Will I get orthorectified photos with this LiDAR product? If so, what is the image resolution?
Yes. Orthorectified imagery is a typical GeoDigital deliverable. While typical image resolution on the ground plane is 10 – 15 cm, the actual resolution is determined by our customer's specifications.
What potential problems must be considered during the planning process for a typical LiDAR job?
While the tragedy of 9/11 has definitely created a new norm in the way low-level helicopter flights are conducted, GeoDigital's field operations procedures have always comprised careful pre-flight planning, including proper advance notice to controlling FAA offices, local police and fire departments, media, large account customers and/or the managers of sensitive areas, such as DOE, penitentiaries, power plant managers, etc. It is our unrelenting attention to detail that makes the overall job go smoothly and wins the willing support of everyone along the way.
How wide of a corridor can you map?
GeoDigital operates very fast pulse rate lasers of 50 to 100 KHz units, which allow the aircraft to fly higher with excellent point density on the ground. GeoDigital has the ability to cover any customer-defined corridor width.
How many passes must you make to collect the necessary data?
In almost all cases, depending on the customer requested corridor width, only one pass is required to collect accurate data.
What determines the appropriate laser system for the job?
We start by listening very carefully to our customer's needs and asking the right questions. The customer contract specifications are critically important to determining both the hardware used and the data collection flight profiles.
What is the effect of having the ground stations closer or further apart?
Generally, the effect of ground base stations being positioned closer to one another increases accuracy. However, many other factors do impact the spacing decisions and are considered during the planning stage. The key issues are the terrain and the availability of “pre surveyed” ground control points.
How many miles or km can you survey per day on a corridor?
While daily productivity (miles of corridor per survey day) can become subject to such factors as line voltage and terrain, specification of the final product, width of a corridor, territory (urban, suburban, farm etc.), and rapidly changing weather conditions, GeoDigital typically maintains an average of 100 corridor miles surveyed per day.
How do you measure the temperature of the wires?
GeoDigital uses an indirect method to obtain the temperature of the conductors. During the survey, we operate several ground weather stations to measure and record such parameters as wind speed, wind direction, solar radiation, and ambient air temperature. In addition, we also obtain line load data from the customer. Our proprietary software combines this information with the physical parameters of the conductors. The temperature of the conductor is calculated by applying methodologies approved by CIGRE and IEEE. In comparison to the direct measurements of the conductor temperature, the indirect method proves to be easier and more productive – results which our customers have verified to be extremely accurate as delivered.
What is the minimum voltage or line size that we can do a sag analysis on?
Do you have experience with low voltage single line circuits? GeoDigital has proven time and time again that single strand under build and/or line crossing can be easily surveyed with the higher repetition rate laser.
At what altitude do you typically fly?
Altitude for our survey flights depends on the specifications of the final product we deliver. Typically, for power line mapping, GeoDigital operates at an altitude between 800 – 1200 feet above ground level (AGL).
Does time of year and weather conditions impact a LiDAR survey? What about snow covered ground? Wetlands?
Time of year and weather conditions is always important considerations in the planning for a laser survey. LiDAR survey can be performed during daylight without strong winds (over 15 m/sec), and provided no precipitation or smoke is present to degrade the transmission of light. Optimally, our equipment performs best when ambient air temperature remains above 23° Fahrenheit. Snow covered ground can affect the accuracy of ground positioning measurements as the laser will detect the surface of the snow cover instead of measuring from true ground. Wetlands have similar disparate effect as the laser will measure the surface of the water and not penetrate to the land bed below.
Do you require engineering drawings (as built drawings) and/or other assistance from us in your planning or operations?
GeoDigital appreciates any information our client's wish to contribute during the permission planning stage. This includes engineering drawings, existing GIS, towers/structures drawings, and any information to accurately identify circuits, lines, or substations.
Can we provide our own helicopter?
Yes, if you prefer. GeoDigital uses a Bell-206 “JetRanger” for survey operations due to its excellent reliability record and availability anywhere in the world. GeoDigital's LIDAR equipment is STC approved on the Bell 206, and we provide all pilots with the training essential to collecting accurate and consistent data.
Can this service be provided by a fixed wing aircraft? What are the options?
For wide area surveys – yes. For typical power line surveys (corridor survey) – no. The helicopter is simply the best aerial platform for corridor work. GeoDigital's pilots position the aircraft over the lines using an internal GPS navigation system and by visual reference to the ground. Fixed wing aircraft provide extremely limited views of the power line from the pilot's seat, thus limiting the ability of the pilot to navigate the power line visually. We know some companies use aircraft for this purpose, but we strongly feel a helicopter platform is best suited to delivering better corridor data for our customers.
Do you propose leasing a local helicopter provider or do you ferry in your own helicopter?
GeoDigital prefers to lease helicopters from local companies to keep customer costs to a minimum. Also, to increase efficiency and safety, GeoDigital always considers using local pilots as the first option.
How quickly can we start after contract award?
The typical preparation stage averages two to three weeks after contract award, and we always strive to satisfy customers with time-sensitive needs.
How many people are in the aircraft? Do you require a customer representative in the aircraft?
Typically there is a pilot, an observer/navigator and a LiDAR systems operator onboard the aircraft. A customer representative is not required to be aboard the aircraft, but GeoDigital does request our customer's assistance during the flight-planning phase of operations. This is the key to delivering a successful and cost effective mission - for both vendor and customer!
How many people are on the typical field crew? Do you require a customer representative as part of the field crew?
This totally depends on the scope of the project. Typically, the ground control crew mans the base and weather stations while a separate crew performs flight planning and verification of the completeness of daily data. GeoDigital does not require a customer representative as part of the field crew.
Do you have a separate mobility cost or is everything built into your per mile/km/wide area pricing?
This is determined by customer pricing requirements as outlined in the contract.
Do we get any software as part of the project? Do we have to purchase any special software to be able to use the LiDAR product most efficiently?
GeoDigital LiDAR data is configured and formatted, ready to use in any GIS or CAD software (PLS-CADD, AutoCAD, MicroStation, ArcView, etc.). If our customer prefers to use its own “in house” software, such as PLS-CAD for data management, GeoDigital's deliverables will be prepared in PLS-CAD ready files.
What is the minimum size job you will perform? (Both corridor and wide area)
GeoDigital will consider any size project, which in the most modest cases may be 25-50 miles. As is the case with most service providers, price per unit decreases as volume increases. For corridors, mobilization costs becomes minor at about 300 miles.
How fast will we get our data back? What is the collection to processing ratio?
Our typical data processing rate for a customer is 300 miles a month, but this can be increased if the customer advises us of any special requirements.