Aerial Imagery & Lidar in the Yukon Delta, Alaska

Mapping from Earth, Sky, and Space

Newsletter from Continental Mapping Consultants, Inc. 2014 Volume 1

The Yukon Delta National Wildlife Refuge near Bethel, Alaska is a 22 million acre conservation area of flat tundra where the Yukon and Kuskokwim Rivers and their tributaries stitch a winding path to the Bering Sea. The rivers create a varied landscape of islands and plains, ponds and sloughs, making a waterfowl habitat of worldwide significance for shorebirds, large mammals like bear and muskox, and spawning grounds for 44 species of fish. The US Fish and Wildlife Service (FWS) is studying the Kwethluk and Tuluksak Rivers within the Refuge due to potentially contaminated runoff from 100+ year old mines upstream. FWS contracted Continental Mapping to complete a high resolution aerial lidar survey and high resolution orthophotos to support habitat modeling and hydraulic studies. Continued on Page 3…

Mapping Speci�cations Development and the Problem of Abstraction: Lessons from the Surveying and Mapping Trenches

The development of specifications is a challenge in survey and mapping. In the last few years, as new technologies and methods have been integrated, Continental Mapping has worked on a range of “spec update” projects. The struggles are profound, and we have changed the way we engage with our clients in order to facilitate a better understanding of a project’s needs, requirements, and deliverables.

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Urban transportation projects are typically very complex in their requirements, timelines, and site conditions. Surveying and mapping is just one component of the overall project. These projects have compressed schedules, complex design challenges, varying accuracy requirements throughout, and heightened concerns over survey crew and motorist safety due to high traffic counts. Continental Mapping addresses these issues by combining multiple platforms, sensors, and field techniques (i.e. data fusion), as it eliminates redundancy and leverages the strengths of each. Aerial imagery supports the mapping, aerial lidar penetrates obscured areas, mobile lidar provides roadway features with the aid of terrestrial photography, and land survey ties it all down and collects supplemental data. Together, critical delivery schedules are met within the accuracy expectations of the design engineer. Case in point is a Tennessee Department of Transportation Project (TDOT) along SR 71 in Knox County, Tennessee. This state highway winds through hilly terrain of residential and commercial properties and contains complex utility infrastructure and visibility issues, limited shoulder for surveyor safety, and heavily vegetated areas within the right of way; all requiring survey grade engineering data.

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Mobile Lidar, Aerial Photogrammetry and Survey: Data Fusion for TDOT

Dave Hart, CP, SP, RPP - President

Continental Mapping Consultants, Inc.

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ALTA, Boundary and Hydrographic Surveying Projects

Data Fusion for TDOT continued…

Mapping from Earth, Sky, and Space

To meet these needs, TDOT requested high accuracy mobile lidar (0.1-foot) on hard surfaces, aerial lidar for penetration of the wooded areas, as well as aerial imagery for color orthophotography, 1” = 50’ scale planimetrics, and 1’ contours. As an additional bonus, multiple platforms and sensors ensured accurate design data in step with the overall project schedule. Several waves of proj ect control were completed: initial project control, ground control for the aerial imagery and airborne lidar, and survey ed calibration points along the road shoulders for mobile mapping. Aerial acquisition occurred after photogrammetric control and mobile mapping calibration points had been established enabling the image processing to include an enhanced control solution of both aerial and mobile control.

Our survey crews continue to complete a variety of different projects across the country. Below are a few examples.

Hydrographic Survey for the Black River, Missouri FEMA identified changes along 46 miles of the Black River in Butler County, Missouri that led them to believe that the levee in Poplar Bluff was no longer adequate in the event of a flood. To rectify this issue, FEMA required a new modeling effort which included full survey of the flowline of the river via echosounder as well as a survey of 27 cross sections (some from water’s edge and others bank-to-bank) and over 2 dozen bridges and drainage structures. Continental Mapping’s survey deliverables supported modeling using HEC-RAS.

ALTA Survey at Tinker Air Force Base, GM Assembly Plant, Oklahoma The City of Altus, Oklahoma entered into an agreement with the US Army Corps of Engineers (USACE), Tulsa District to sell the General Motors Assembly plant property to the Corps of Engineers. Prior to the purchase going through, USACE wanted a new ALTA/ASCM Land Title Survey completed for the 440 acre site. Continental Mapping combined high accuracy aerial imagery with a comprehensive survey effort which included: research of legal descriptions, analysis of prior surveys and records, and a full field survey.

Levee Surveys in Spring Valley, Wisconsin and Carroll County, Indiana FEMA required both natural channel and structure surveys for the Spring Valley levee along Mines Creek in Spring Valley, Wisconsin and the Delphi levee in Carroll County, Indiana. Survey work included bank-to-bank surveys, structure surveys, and field notes. Photos and sketches were completed in accordance with FEMA’s Guidelines and Specifications for Flood Hazard Mapping.

Boundary Survey at Great Salt Plains Lake, Oklahoma The US Army Corps of Engineers (USACE), Tulsa District had the need to reestablish specific boundary lines of property owned by the Government along the Great Salt Plains Lake in Oklahoma. Continental Mapping’s survey team researched legal descriptions, reset missing or destroyed monuments, and completed a full plat of survey along the boundary lines in question.

Finding the ideal e for data acquis on proved to be a tremendous challenge, as the window is limited between snowmelt and leaf-out. Data was successfully acquired in the fall of 2013 and processing began shortly therewith delivery in early 2014. The flat, complicated landscape proved to be a challenge to process as tree-lined islands were crisscrossed by numerous streams and rivers.

Mine tailings are easily iden fiable in the high resolu n orthophotos developed for this project

Merged orthophoto and aerial lidar point cloud

Con nental Mapping staff developed several specialized workflows to aid in lidar point classi on and in delinea ng river boundaries to ensure mapping completeness and accuracy at a level that supported the modeling needs of scien sts. Deliverables included a hydro-enforced lidar surface and color orthophotos. The accuracy of the deliverables was 0.60' ve al accuracy at a 95% confidence interval (per ASPRS accuracy guidelines). The US FWS and other organiza ons ac ve in the Refuge now have current and accurate geospa data to aid their resource management ac vi es.

Headings • 2014 Volume 1

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Mapping from Earth, Sky, and Space

Yukon Delta, Alaska continued… Open Positions Con nental Mapping has openings for mu ple geospa analysts in our Sun Prairie, Wisconsin HQ office. Go to www.con nentalmapping.com for details and please pass the word along if you know of anyone looking for work.

Abstraction & Speci cations continued…

The scales at which we deliver data vary from small site surveys to global scale mapping deliverables. In all of these, we have found key concepts that always hold true and we have learned lessons that directly apply to any project. De ne the Need. In all cases, three driving factors determine the need

for mapping, we’ve termed them the three Cs: currency, clarity (resolu on, accuracy), and content (features). Defining the need establishes the framework for geospa data colle on.

Determine Criticality. This is key to valida ng the first step of the process, and o n resets the discussion. As a map is a generaliza on and simpli on, everything can’t be cri

Constrain to Budget. Once a budget is introduced, what is truly crican be defined and expecta ons for referen al features are o n relaxed.

Database Design. In almost every instance, people are inclined to build on what exists (bo om up) and things quickly unravel. A top-down database development methodology should be used that covers conceptual design (addressing solu ons to a problem), logical design (defining en es, as well as rela nships and linkages between en es), and physical design (very involved work including Level of Detail concepts as seen in BIM).

Develop Measures of Acceptance. This is the last and most important part of the process. Here, standards and acceptance parameters are coupled with specifica ns and guidance. It is taking “fit for use” concepts and developing evalua n processes to determine acceptability of the data. The most problema issues here deal with just three elements: completeness, thema classi on correctness, and non-quan ta ve a bute correctness. Each of these elements is a problem of abstra on (making them subjec ve) and therefore their evalua n cannot be automated, which o n leads to a biased review. We have done original research that proves this (for another ar le!).

Most organiza ons undergoing spec updates stumble out of the gate. All eventually realize the need to develop a formal process that helps establish scalable and constrained specs that help them deliver their program. Our experience in this process is expanding rapidly. Please give us a call if you’d like more stories of our experience in the spec development trenches. Expanded discussion online www.continentalmapping.com/news/specupdates

UAS Podcast Con nental Mapping staff were interviewed on the UAV Podcast about our UAS community outreach project. Give it a listen at www.theuavdigest.com episode UAV032.

Dredge picture courtesy of Alaska Historical Society