Longitudinal Sectioning

Longitudinal sectioning, also known as profile leveling or profiling, is the process of establishing the elevation of sites on the ground at about regular intervals along a continuous line. Profile levelling is one of the surveyor’s most typical applications of running levels and vertical distance measuring. The data are represented as a profile, which is a representation of a vertical cross section. The primary objective of longitudinal sectioning is to determine the slope, grade, and vertical alignment of the surveyed feature.

• Taking elevation measurements: At regular intervals along the base line, surveyors measure the elevation of the ground surface using an instrument like a leveling instrument or a total station. These measurements are recorded to create a profile of the land.

• Plotting the profile: The collected elevation data is plotted on graph paper or entered into specialized software to create a longitudinal section. The resulting graph shows the variations in ground level along the surveyed line.

Cross Sectioning

Cross sectioning involves the creation of horizontal cross-sectional views of the land perpendicular to the alignment being surveyed. This technique provides valuable information about the terrain’s shape, dimensions, and features at specific locations. Cross sections are particularly useful for designing and analyzing infrastructure elements like roads, canals, or embankments.

• Establishing cross-section lines: Surveyors mark perpendicular lines to the alignment being surveyed at regular intervals. These lines are known as cross-section lines or station lines.

• Taking measurements: Along each cross-section line, surveyors measure the ground level at predetermined intervals using leveling instruments or total stations. Additional measurements may be taken for features such as buildings, utilities, or natural elements.

• Plotting the cross section: The measured data is then plotted on graph paper or entered into specialized software to create a cross section. The resulting diagram provides a detailed view of the land’s features and elevations along the surveyed line.

Applications

Longitudinal and cross sectioning have numerous applications in surveying and civil engineering projects:

• Road construction: Longitudinal and cross sectioning techniques are extensively used in road surveys for designing alignments, establishing grades, and determining cut and fill quantities for earthwork calculations.
• Drainage systems: The creation of longitudinal and cross-sectional profiles helps in designing efficient drainage systems by identifying the natural flow patterns and locating appropriate points for channeling water.
• Utility infrastructure: Surveying utilities, such as pipelines or electrical cables, using longitudinal and cross sectioning helps in planning their alignment, estimating trench volumes, and identifying potential conflicts with existing infrastructure.
• Land development: When planning residential or commercial developments, longitudinal and cross-sectional surveys provide valuable information for site grading, building placement, and determining drainage patterns.

Benefits

• Accurate data: These techniques allow surveyors to gather precise elevation and terrain data, providing a solid foundation for engineering design and decision-making.
• Efficient design: Longitudinal and cross-sectional surveys facilitate the design of infrastructure elements, enabling engineers to optimize grades, alignments, and earthwork quantities.
• Enhanced visualization: The graphical representation of longitudinal and cross-sectional data helps stakeholders visualize the project’s topography and understand its impact on the construction process.
• Conflict identification: By identifying potential conflicts, such as steep slopes or underground utilities, early in the surveying process, longitudinal and cross sectioning help avoid costly design revisions during the construction phase.

Longitudinal and cross sectioning techniques play a vital role in surveying, providing valuable data for civil engineering projects. The detailed profiles and cross sections derived from these surveys aid in optimizing alignments, grades, and earthwork quantities while minimizing conflicts and ensuring efficient project execution.

What is a photogrammetry software?

Photogrammetry software is a computer program that provides the tools for performing photogrammetric measurements, such as loading photos from your camera and producing accurate measurements, maps, and models from those photos. In drone technology, photogrammetry sensors are typically high-resolution cameras that take pictures from various angles while flying over the area of interest. A 3D point cloud of the terrain or object is then produced by stitching together these images using specialized software. This point cloud can then be further processed to create a full 3D model, allowing anyone to view it from any angle as if they were physically holding it in their hands. The software to process these images can be desktop or cloud-based.

Cloud-Based Photogrammetry Software

Cloud-based photogrammetry software refers to applications that leverage cloud computing resources for processing and storing data related to photogrammetry. Cloud-based survey software makes it easier for companies to create surveys and receive responses quickly, making the entire process cost-effective. Compared to locally based solutions, cloud-based survey software doesn’t require a particular computer as it can be used online using a web browser.

Salient Features of cloud-based photogrammetry Software

• Data Upload: Users can upload their images or datasets to the cloud platform for processing. The software may support various image formats and offer tools for organizing and managing the data.
• Data Processing: The cloud-based software uses powerful computational resources in the cloud to perform photogrammetric processing tasks. These tasks include feature extraction, image matching, triangulation, dense point cloud generation, and mesh reconstruction.
• Automation and Optimization: Cloud-based photogrammetry software often includes automated processes and optimization algorithms to streamline the photogrammetric workflow. These features help improve the accuracy and efficiency of data processing.
• Visualization and Analysis: The software lets users visualize and analyze the photogrammetric results once the processing is complete. This may include viewing 3D models, orthomosaics, digital surface models, and point clouds, measuring distances, area, and volumes, and extracting specific information from the data.
• Collaboration and Sharing: Cloud-based platforms often provide collaboration features, allowing multiple users to access and work on the same datasets simultaneously. They also enable sharing and distribution of processed data through online galleries, sharing links, or embeddable viewers.

Pros

• Cost-effective: Cloud-based photogrammetry software follows a subscription-based pricing model, allowing users to pay for what they need when needed. This eliminates the need for significant upfront investments and provides more predictable costs.
• Time-saving: Cloud platform reduces risk and automates manual tasks.
• Accessibility: Cloud-based software allows users to access their photogrammetry tools and projects from anywhere with an internet connection. This flexibility benefits remote collaboration, fieldwork, or accessing projects on different devices.
• High accuracy and detail: Cloud Photogrammetry software can produce highly accurate and detailed 3D models and point clouds with high-resolution images and appropriate processing techniques.
• Flexibility and scalability: Photogrammetry software offers flexibility regarding the type of imagery it can process, such as aerial or ground-based photos, and can handle large datasets. Cloud-based solutions often offer scalable processing power and storage. You can easily handle large datasets and complex projects without investing in expensive hardware upgrades.
• Storage and Data Security: The data can be accessed anytime, anywhere since the data is stored in the cloud. There is no risk of losing the data.
• Collaboration: Cloud-based platforms enable real-time collaboration and data sharing among team members or stakeholders. Multiple users can simultaneously work on the same project, facilitating efficient teamwork and feedback exchange.
• Automatic Updates: Cloud-based software providers can release updates and improvements seamlessly without requiring users to install them manually. This ensures users can access the latest features and enhancements without additional effort.
• Integration: All outputs can be downloaded and exported to third-party CAD and GIS software for further analysis.

Cons

• Internet Dependency: Cloud-based software heavily relies on internet connectivity. If you have a slow or unreliable internet connection, it can hinder your ability to upload and process large image datasets efficiently.
• Data Security: Storing data in the cloud may raise concerns about data security and privacy. It’s essential to ensure that the chosen cloud provider has robust security measures and complies with industry standards and regulations.
• Data Transfer and Upload Times: Uploading large image datasets to the cloud can be time-consuming, particularly if you have limited bandwidth. This process may introduce delays before you can start processing your photogrammetry projects.
• Limited Offline Functionality: Cloud-based software generally requires an internet connection to access and use the tools. If you work in an area with limited connectivity, you may be unable to work on your projects or access your data.
• Dependency on Service Provider: When using cloud-based software, you depend on the service provider’s availability and performance. Any downtime or technical issues on their end can impact your ability to work on your projects.

The previous SOP only mentioned submitting the Digital Elevation Model (3D), i.e., Digital Surface Model and Digital Terrain Model. In the new updated SOP, it has been made clear that the Digital Elevation Model (3D), i.e., Digital Surface Model and Digital Terrain Model, should include the 100m buffer zone. The spatial resolution of the image has also been defined, which should be less than or equal to 15cm in UTM Projected Coordinate System and in Geotiff format.

Compared with the Previous SOP, the new updated SOP clearly defines the GCPs that must be submitted to IBM. The new updated SOP has divided the GCPs that must be submitted to IBM into three files.

1.                 The total GCPs DGPS Survey data, including permanent GCPs, must be submitted to IBM in GCS                      WGS-84 datum and UTM Projected Coordinate System in Excel Format.
2.                 The Permanent GCP data needs to be submitted to IBM both in GCS WGS-84 datum, and UTM                          Projected Coordinate System in Excel Format.
3.                 The plan of GCPs needs to be submitted to IBM in UTM Projected Coordinate System in shapefile                      format.

• In the new SOP, submitting the RMSE report in .txt, .doc, and .pdf format has been mandatory. Earlier, the RMSE report needed to be submitted only in .txt and .doc format.
• There are also major updates in the map of the mining lease area. More features have been added to the map that needs to be marked in the map before submitting it to IBM. The updated features are listed below.

1. 1. ML Boundary
2. 2. Topsoil stack
3. 3. Infrastructure
4. 4. Roads
5. 5. Railways
6. 6. Tailing Pond
7. 7. Effluent Treatment Plant
8. 8. Mineral Separation Plant
9. 9. Township Area
10. 10. Others to specify (Green Belt area)

In the previous SOP, the Boundary Pillar coordinates must be submitted in the shapefile and Excel format in Geographic Coordinate System and Projected Coordinate System. In the new updated SOP, the boundary pillar coordinates must be submitted in Excel format in GCS and UTM. Also, a plan of the leased boundary pillar coordinates also needs to be submitted in UTM and GCS in WGS 84 datum. Although here, two separate shapefiles for GCS and UTM must be submitted.

Finally, As per the previous SOP, the Drone Survey Log Sheet needed to be submitted only in the .doc format, while in the new updated SOP, it has been made clear that the drone survey log sheet needs to be submitted both in .doc and pdf format.

10. Data Output and Formats

The outputs that need to be submitted are discussed below:

11. Submission of Data to IBM

The processed output data of the drone survey shall be submitted in soft copy only in storage media (i.e., external hard disk) on or before 1st July every year along with the Output data submission form at the following addresses.

1. The Chief Mining Geologist, Indian Bureau of Mines, GM&MM Cell, 1st Floor, A- Block Indira Bhavan, Civil Lines, Nagpur- 440001, Maharashtra
2. Respective Regional Offices Indian Bureau of Mines

Pre Site Planning

On Site operations

Planning just the KML is not enough. We must also be aware of other parameters significantly affecting the results while mapping large areas.

Front Overlap: The overlap between successive photographs on a flight path is called front overlap. Increasing the front overlap makes the camera capture more photos quickly. It only affects the number of images.

Side Overlap: The overlap between photographs in adjacent parallel flight paths is called the side overlap. Increasing the side overlap gives more matched features in the imagery but reduces the area your drone can cover in one flight. The flight duration also increases as the number of lines increases.

The formula to calculate GSD is (flight altitude X sensor height) / (focal length X image height and width).

Low altitude and high-resolution sensors will give low GSD. Lower GSD results in higher accuracy.

Data Collection

Linear Mission

Linear missions are used to survey roads, corridors, canals, etc. It is used to analyze line-type features. The default mission shape is a line. Here you can increase the lines according to your mission, place them accordingly, and start the mission. Once the area is marked, and the altitude and lines are set, the drone will automatically fly to the initial point and begin its mission. After reaching the endpoint, it will return to its home position.

Circular Mission

Buildings/Monuments are mapped using the circular mission. It takes a circular flight path, allowing it to capture images from all angles. Once the area has been marked, and the altitude is set, the drone will fly to the initial point and begin its mission. It returns to its home position after reaching the endpoint.

How to fly in mines?

Drones in the mining industry are a pragmatic solution to fix daily problems and play a role in reducing human risk, inspections, and repair costs while also increasing efficiency. However, we must exercise caution when flying drones in mines. When compared to traditional ground surveys, aerial surveys have the upper hand.

To get a good field of view, use the Polygon mission and keep the camera facing the ground.

How to fly in hilly areas?

It is possible to fly a drone in the mountains. However, you may encounter challenges in exceptionally high mountains because the air is less dense at higher elevations. Additionally, you can have shorter flight times due to a more considerable drain on your batteries caused by altitude and cold.

Points to note before flying

• Be aware of your surroundings.
• Fly at high altitudes and increase overlap to identify areas with critical features.
• Keep an eye on the weather, especially the wind.
• Choose a safe elevated area as the home position.

How to fly when there are tall trees and dense vegetation?

Drone technology redefines forestry’s components and contributes to forest ecosystems’ development and improvement. It also contributes to wildlife monitoring, Tree disease Detection, Forest fires, etc.

Points to note before flying

• Fly at high altitudes to ensure you have a clear line of sight.
• Place GCPs in areas where the terrain abruptly changes.
• Set the minimum height above ground to the tallest object’s height + 25m.

How to fly when it is windy?

Most drones can fly in strong winds, but it depends on the specifications of your drone.

Points to note before flying

• Maintain a safe distance from buildings and other obstacles.
• Check the wind speed of the site before flying the drone.
• If the drone becomes unstable, try to land as soon as possible or use the return home feature.
• Fly the drone in the wind’s direction.
• Some drones will have fail-safe features, such as an automatic return-to-home feature when the wind speed exceeds a specific limit. If this occurs, do not attempt to fly the drone again.
• Keep a close eye on the battery.