Questions about Contour Lines from HD-LiDAR datasets

We get quite a few questions about the contour lines produced as part of the dataset from our HD-LiDAR process. They are typically described as “jagged” or having too many bends. While most engineers and surveyors are familiar with the concept of what contour lines represent, they are used to contour lines produced based on data collected by a survey crew, which collect data along features and on approximate grids for areas of constant grade. This grid is typically spaced at 50 foot intervals for larger areas, but can vary in density based on field conditions, budgetary constraints and the experience of the field crew. The wide grid scheme, and use of smoothing or splining settings in the computer yield contours which are pretty, but live up to their traditional definition of showing approximate lines of equal elevation. LiDAR data collected at our typical densities yields a grid with spacing of approximately 1 foot.

The increase in density of measurements brings to the table an amazing amount of detail that no surveyor would ever collect due to the time involved. LiDAR data shows small undulations in terrain, particularly in flat areas like parking lots and fields. Another area that shows increased detail is sand dunes, disturbed earth on construction sites, quarries, landfills and stockpile yards. Airborne LiDAR strikes a very efficient balance of covering large areas with a substantial amount of detail without the burden of collecting hundreds or thousands of points per square meter typically yielded by terrestrial scanning units. When the DTM is produced, using breaklines that are all based on 3D points that in essence identical to measurements produced by a survey field crew, the contours reveal a much more accurate and precise representation of field conditions.

To view live HD-LIDAR datasets contact us today - viewable online or we can visit your office.

Haunted by surveying challenges for your active railroad site that contains multiple rail lines?

One of our clients recently had a new transit station project in which the engineering team needed detailed surveys for the design project.  Traditional surveying methods would have involved months of preparation, many railroad safety flaggers and would have resulted in higher costs to the client. 

In just one pass of our aircraft, AXIS was able to map an area with a ground point density of approximately 30 to 40 points per square yard; locating power lines, poles, rail lines, buildings, pipes, curbs, vegetation canopy, overpass/bridge clearances and every other landscape feature within the aircraft’s mapping swath.  The landscape and terrain are mapped with what is called a “Point-Cloud” rather than the traditional CADD-Only map format.

Field surveyors were kept out of harm’s way and the project received mapping information unachievable by any other technological means in a fraction of the time of traditional surveying and mapping methods. This detailed survey was completed in half the time, surpassing traditional surveying methods.  

HD-LiDAR kept land surveyors from having to navigate an active railroad and rail yard, accelerated the schedule by avoiding months of approvals for access by the rail authority and delivered a new type of mapping data the engineers would have never received otherwise.

Visit http://www.axisgeospatial.com/transportation-mapping/ to view some of our recent transportation mapping solutions for design & monitoring projects. Let’s discuss your project goals, objectives, budget and schedule to determine if HD-LiDAR technology is right for your project.  

QA/QC Philosophy not words!

Suppose you are about to – or already have – contracted with a reputable and qualified Geospatial Data Provider on a large project. Is your organization knowledgeable, experienced or capable of reviewing or managing such a complex endeavor? 

Ask yourself these questions:

• Do you have both human & system resources required to review the deliverables when they start streaming in (which they will in mass quantities on large projects)?
• When the AeroTriangulation reports are delivered, who in your organization will review, understand and approve this vital deliverable?
• Will you just simply trust your mapping contractor because they claim ‘…we guarantee the results’?
• Do you understand that you may not see the gross errors in the final data until months or years down the road when you and other agencies are using the data?
• Where will your mapping contractor be then? Will they still be there to fix the data?
• Will there be litigation in order to correct and resolve the errors?
• Will you be pointed out as the “failed project manager”?

Don’t manage a project with complex and costly deliverables on your own unless you have the resources to successfully do so. Axis GeoSpatial has certified project managers, certified photogrammetrists and other trained professionals to assist you in managing your geospatial project to a successful and reliable completion.

Not only do we possess the production equipment and expertise, we dedicate QA/QC tools and personnel that specialize in Quality Assurance. Because we understand all aspects of geospatial production including common errors and omissions, Axis can more easily and reliably identify issues and further communicate more effectively and cooperatively with your mapping contractor. We also can do it in a timely manner thereby mitigating scope creep and scheduling delays.

Get the second opinion – view the quality of your GeoSpatial Data through our eyes.

Contact Us to discuss an independent QA/QC report on your next project.

Field QA/QC Process

As a routine process of a project, Axis calls upon its in house survey team to not only provide precise and accurate survey control for photogrammetric and airborne LiDAR data sets, but to also provide the true analysis and cross checking of those datasets. 

Once a project has been controlled and adjusted to the ground and appropriate project datum’s, additional points of interest are identified, typically by project geometry or guided by project specifications requiring checks in different ground cover classifications. This last method involves identifying land cover and use classifications, such as wetlands, deciduous or coniferous wooded areas, cultivated areas or residential areas and then gathering specific data points in those areas to assess and verify that the location and elevation data represented by the airborne dataset is correct. This procedure involves establishing GNSS control, and then precision stakeout of a point of interest to verify its three-dimensional location.

Documentation of this process includes gathering metadata that will show measurement details, control ties, conventional photographic evidence of the general area, as well as through the scope of the instrument to prove aiming accuracy. Through the scope photographs are directly linked to a point of measurement, and include the display of the instrument crosshairs as they are pointed at the prism or point of measurement.

For more information contact AXIS today www.axisgeospatial.com/contact-us