Photogrammetry & LiDAR

Eratost offers complete solutions for all standard tasks in the field of digital photogrammetry, DEM/DTM generation, stereo compilation, aerial triangulation, extraction of topographic and planimetric features, orthophoto production, color balance, mosaic and mosaic generation, sharpness bread, orthophoto services, 3D terrain visualization, and LiDAR data processing.

There is no doubt that both technologies deliver much faster results and data density compared to traditional topography methods (both techniques measure all visible objects without interpolation). However, the selection of the best technology for your project depends, among other things, on the application, the environmental conditions, the delivery times and the budget. This publication provides a detailed description of the strengths and limitations of LiDAR and photogrammetry to help you choose the right solution for your project.

How Do Both Technologies Work?

LiDAR (Light Detection and Ranging) is a laser-based technology. Shoot the laser and measure the time it takes for the light to return. It is referred to as an active sensor because it emits its energy source instead of sensing the energy emitted by objects on the floor.

Photogrammetry, on the other hand, is a passive technology based on images transformed from 2D cartometric to 3D models. It uses the same principle as human eyes or 3D video to create depth perception so that the user can see and measure objects in three dimensions. The limitation of photogrammetry is that only points can be generated that are based on what the camera sensor can recognize through ambient light.

Leading Results And Photogrammetry Surveys

The main services of the LiDAR survey is a cloud of 3D points. The density of the point cloud depends on the properties of the sensor (sampling frequency and repetition rate) and on the flight parameters. Assuming the scanner is pushing and oscillating at a fixed speed, the density of the point cloud depends on the altitude and the speed of the aircraft.

Different point cloud parameters may be required for multiple use cases. For example, to model power lines, you may want to have a dense point cloud with more than 100 points per square meter while building a digital terrain model. In a rural area, 10 pts / m2 cloud is enough.

It is also important to understand that the LiDAR sensor only displays positions without RGB, which creates a monochromatic data set that may be difficult to interpret. To increase the informative value, data are often displayed with false colors based on the reflectivity or the height.

Accuracy

Let’s start with the definition of accuracy. In topography, precision always has two dimensions: relative and absolute. Relative accuracy is the measurement of how objects are positioned relative to one another. Absolute precision refers to the difference between the position of objects and their true position on Earth.

Eratost integrates LiDAR data seamlessly with other data sets, including orthophoto images. We can combine LiDAR with GIS data and other surveying information to generate complex geomorphic structure mapping products, advanced 3D models / earthmoving profiles, structural representations and many other high-quality mapping products.

The core of our competence lies in the experience of offering spatial solutions for a wide range of customers

We integrate knowledge, technology, people and companies with geographic regions to develop innovative and potential services for local and global customers. Our services enable accurate and inexpensive data acquisition, which proves to be an important input for the planning and design of photogrammetry and LiDAR projects.

Aerotringulation

Aerial triangulation is the calculation of the actual terrain coordinates, which is used as a basic reference in photogrammetry. Triangulation from the air is the process of compressing and expanding ground control by means of mathematical means. AT extends the horizontal and vertical control from relatively few ground detection control points to any unknown terrain point that is included in the solution. Additional control points are referred to as connection points and are used to control the subsequent photogrammetric image. Each stereo model is scaled and leveled using the adjusted coordinate values of the waypoints in the stereo model. i-Infotech offers complete triangulation services for paper copies from the air and offers very precise control for card production. Digital images are uploaded to electronic copy workstations. To control the triangulation solution, GPS coordinates are used in the control points for air and ground investigations.

We offer precise 3D Design and modeling services for:
  • Line map of the project area showing flight lines
  • Project boundaries
  • Control point locations and identification numbers
  • Description of the ground control points with coordinates
  • Camera calibration report
  • Technical specifications
  • Estimates of the horizontal and vertical accuracy of the ground control points

Digital Terrain Mapping / Digital Elevation Model / DTM Model

The digital elevation model (DEM) is a representation of the earth relief used for geodata analysis and modeling. Elevation data are recorded in the form of points with a defined interval and cutting lines. Digital elevation models are usually created as an important basis for the planning and construction of infrastructures such as roads and railways.

In connection with excavations, open-cast mining and the preparation of landfills, the change in the soil can be documented by repeated measurement of digital elevation models and changes in volume can be calculated.

Eratost has derived a number of digital and graphic products from a digital elevation model, including:

  • Height interpolation at any point on the ground
  • Plots of contours with user-specified contour intervals
  • Control point locations and identification numbers
  • Generation of longitudinal and cross-section profiles
  • Plots of isometric and perspective images
  • Volume calculations, including computation of cut and fill

Using photogrammetric software, a dense cloud of height points is generated in several images by automated height detection (correlation). The results are checked manually with powerful processing tools. Highlights in artificial structures or vegetation can be removed and gaps can be closed. The last step is to generate DTM.

Planimetry

Eratost has state-of-the-art photogrammetric mapping functions. Before starting a vector compilation project, an accurate estimate of the time, effort, and duration of the project is made. To analyze project requirements and customer expectations, we review the project against standards and specifications documented in accordance with an ISO 9001: 2000 certified process to ensure a smooth production process.

According to the project specifications and customer requirements, various types of features (buildings, streets, shafts, drains, lampposts, streams, fences and parking lots, etc.) are captured / digitally in digital photogrammetric workstations using scanned images. Eratost has successfully carried out many projects with new mapping (large-scale projects) and updated the work with high precision.

Orthophoto

An orthophoto is an aerial photo in the color that has been geometrically and geographically corrected so that it overlaps in one plane. The production of orthophotography consists of correcting the distortions of the images caused by the relief of the floor surface.

Digital orthophotos are used as maps for visual identification, also in combination with other cartographic products such as DTM and contours.

In Eratost we generate a digital orthophoto that achieves the best possible resolution of the original aerial photo with continuous color. Apply various image enhancement and edge sharpening routines using special image processing techniques.

The process includes color/contrast and plumage combination techniques to ensure a practically perfect mosaic. Many images can be juxtaposed and rescanned to create a general image file that complements the original orthoimages. Accuracy is measured by comparing the ground position of the ground control point to the true coordinates of the point.

In Eratost, we create an orthophoto with a pixel size of 10 cm, 20 cm, 40 cm. We also work with RGB and infrared images.

Classification with LiDAR

Lidar mapping and topographies are used for forestry, flood risk mapping, oil and gas exploration surveys, transmission planning for power lines or pipeline corridors, design studies, property development, mapping of coastal areas, wetlands, etc. Restricted access areas, city modeling, etc. The use of air detection and light area technology (LiDAR) enables fast and high-resolution acquisition of surface elevation data that are suitable for a variety of applications.

The data is sorted at the end of the processing cycle. This task processes data points through an intensive filtering process and isolates some types of points. For example, vegetation data can be removed from the soil layer data. You can also use a custom filter routine to separate buildings from power lines.

Our classification services include:

  • Bare-rural classification
  • DSM and building footprint classification
  • Classification of the power line/transmission line

Generation of vectors by LiDAR

Vector mapping is a 3D representation of the properties of the earth’s surface, which is used for spatial modeling and analysis.. Prepare the map by extracting vector or time information from railways, buildings, hydrological features, vegetation, etc., as requested by the user using various symbols (trees, fountains, piles, etc.), line types (rail, road), streams, etc.) and regions (buildings, tanks, forests, etc.) with ID.

Digital vector map products are representations of the main features of the topographic map with data from the dashed line and the assigned region/area. Vector maps are digitized so that a geographic information system can automatically retrieve information about the properties of the vector that enable it to be analyzed later (e.g. analysis of neighborhood, proximity and connectivity).

Contour mapping with LiDAR

Contours are usually available in vector formats (e.g. shapefile, DXF) and are derived from a reconstructed TIN-DEM. The contours are one of the most common terms used in surveys. Eratost, contours derived directly from LiDAR data are accurate, but not “clean” and often require a degree of interpolation, simplification, smoothing or manual processing in order to obtain the intuitive product. During the cleanup and editing process, vector specifications have a significant impact on the accuracy of the LiDAR data. This is a direct result, which is often used in technical and other common terms. In many projects, data is collected to “support the creation of 2-foot contours” or similar explanations required to achieve pleasant contours with the accuracy of the basic LiDAR data; The widespread use and generation of contours continue to play an important role in determining the level of accuracy of LiDAR data collections.

3D modeling with LiDAR

Our main functions include 3D visualization, 3D environment modeling, reconstruction of real 3D landscapes, integration of visual and virtual reality as well as real-time roaming with large amounts of data.

In Eratost we recognize: “What you see is what you get!”

Our main functions include 3D visualization, 3D environment modeling, reconstruction of real 3D landscapes, integration of visual and virtual reality as well as real-time roaming with large amounts of data. These 3D modeling techniques are widely used in:

  • Urban development planning
  • Civil engineering planning and planning
  • Local government at different levels
  • Intelligent transport management system
  • Real estate development and management
  • Integrated management of neighborhoods and residential areas
  • Environmental protection systems
  • Land Use Management
  • Exploration and management of natural resources
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