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CASE STUDY

NEPC Mapping in the World’s Highest Mountain Range with Correlator3D


NEPC based in India acquires and processes imagery all over the country. This often takes them to some of the highest habitable places in the world. Here variations in terrain, altitude, and climatological conditions demand rigorous planning. As teams of drone pilots are called in to capture large areas within a very short timeframe, there is no room for a missed opportunity. Once the data is received from the field, Correlator3D is their “go-to” software for creating high-quality mapping deliverables.  

 

Highest Post office
INDUSTRY

Surveying


COUNTRY

India


USE CASE

Mapping large projects in extreme terrain with multiple drones. 


CHALLENGES
  • Choosing the right drone and payload
  • Flight planning for extreme terrain 
  • Climatological considerations 
  • Crew deployment


BENEFITS
  • Proper planning ensures success
  • Contingencies allow teams to stay onsite and complete projects 
  • Local knowledge is an advantage 
  • Delivering projects of any size and in any terrain
Nektor Engineers & Project Consultants
Krishn Pethani

“Our projects bring a lot of variation with them. The ability to work through the photogrammetric processing steps, ensuring data accuracy along the way is extremely important to us. Correlator3D allows this to happen and is much faster than another solution we’ve found.”

KRISHN PETHANI

CHIEF TECHNICAL OFFICER WITH NEKTOR ENGINEERS & PROJECT CONSULTANTS

Quality Report Image Tie Points

Good indicator of sufficient overlap

WORKFLOW


When working with image datasets that were captured in extreme terrain, Correlator3D has many tools that can be used along the way to ensure a quality mapping project.

Once the imagery, their exterior orientation, and camera parameters are imported in the software, the aerial triangulation (AT) process can begin. Once AT is complete, quality reports show different metrics including the number of tie points per image. This is a good indicator of sufficient overlap, which is crucial in extreme terrain. 

The next step is DSM generation, where the software will automatically calculate the optimal GSD for the project. When working in extreme terrain, GSD is a function of flying height. Since pixels cannot be split, the GSD will be limited to the biggest difference in distance to the ground from any image in the project. This can be compared with the project specifications. Flying with terrain following will often result in a better GSD. 

GSD from DSM

With maximal selected, absolute GSD can be found. However, for processing, it is always recommended to use the optimal selection which is approximately 3x the GSD.

Ortho Settings

With maximal selected, overall project overlap can be seen. However, it is best to use optimal when processing which defaults to 30%. Note also the resolution of the Ortho defaults to the GSD of the DSM being used.

In the orthorectification step, the average overlap is calculated by Correlator3D across a range of images and helps decide what percentage to use for creating the orthorectified images. In general, it is best to use as much overlap as possible, to give the mosaic creation process more data to work with when creating seamlines. 

DELIVERABLES

Typical mapping deliverables include digital surface models, digital terrain models and orthomosaics.  

 

BENEFITS

Correlator3D allows full control over the photogrammetric mapping process. Those working in difficult terrain such as NEPC can thus check the datasets being processed for accuracy throughout the entire process. This is important when one error in a step while processing 1000’s of images could cost valuable time. 

 

ABOUT NEPC

Nektor Engineers and Project Consultants understand that the universe of possibilities knows no bounds when guided by innovation, hard work, and unwavering commitment. At NEPC, we engineer infrastructure that nurtures thriving communities, guided by our social and environmental responsibility commitment. For more information, visit www.nepc.in.

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