Aerial Photography and Surveying Quiz
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Questions and Answers

What is the minimum scale required if the measurements are 0.0125 mm and 100 mm?

0.000125

If the average scale required is 1:6000 with a focal length of 152.4 mm, what is the formula to determine the flying height?

The formula is $S = \frac{f}{H-h_{avg}}$.

Calculate the required flying height if $S = 1:6000$, $f = 152.4 mm$, and $h_{avg} = 425 m$.

The required flying height $H$ is 1340 m.

What is the relationship between photographic scale and flying height?

<p>The flying height increases with a decrease in photographic scale.</p> Signup and view all the answers

If the average elevation of the terrain is 425 m, what adjustments need to be made to calculate the flying height?

<p>Subtract the average elevation from the flying height.</p> Signup and view all the answers

Why is it important to know the ground coverage of a photograph?

<p>It determines how much area will be captured in a single photographic image.</p> Signup and view all the answers

What is the significance of having a focal length of 152.4 mm for aerial photography in relation to scale?

<p>It provides a specific measurement that directly influences the photographic scale.</p> Signup and view all the answers

How can shadows assist in conducting aerial surveys?

<p>Shadows can help identify tree species and locate features like fenceposts and power poles.</p> Signup and view all the answers

What is the purpose of a flight map in aerial photography?

<p>A flight map shows project boundaries and the flight lines the pilot must follow for proper coverage.</p> Signup and view all the answers

What role does GPS play in pilot navigation during aerial surveys?

<p>An airborne GPS guides the aircraft along predefined flight lines for accurate coverage.</p> Signup and view all the answers

How should flight lines be oriented for rectangular areas?

<p>Flight lines should ideally be aligned north-south or east-west to facilitate navigation.</p> Signup and view all the answers

What is the significance of transparent flight planning templates?

<p>Transparent templates help plan economical coverage and determine exposure stations.</p> Signup and view all the answers

Why is ground control important in aerial photogrammetry?

<p>Ground control relates aerial photographs to the ground and is essential in photogrammetric work.</p> Signup and view all the answers

What defines a Ground Control Point (GCP) in aerial surveys?

<p>A GCP is any point with known positions in a reference system and identifiable in photographs.</p> Signup and view all the answers

How do aircraft-mounted GPS/INS systems contribute to photogrammetric surveys?

<p>They measure the camera's position and attitude during acquisition to ensure accurate data.</p> Signup and view all the answers

What factors must be considered before preparing a flight map for aerial photography?

<p>Camera focal length, photo scale, end lap, and side lap must be set before map preparation.</p> Signup and view all the answers

What are the three types of control points used in photogrammetry?

<p>Horizontal Control Points, Vertical Control Points, Full Control Points.</p> Signup and view all the answers

How does the accuracy of photogrammetric products relate to ground control?

<p>The accuracy of finished photogrammetric products can be no better than the ground control.</p> Signup and view all the answers

List the main categories of efforts and materials considered in cost estimation.

<p>Labour, materials, overhead, profit.</p> Signup and view all the answers

What factors influence the scheduling of a project phase after estimating hours?

<p>Number of instruments or workstations, trained personnel available, other work in progress, urgency of the project.</p> Signup and view all the answers

What role does experience with similar projects play in estimating cost and scheduling?

<p>Experience is essential for accurately estimating costs and developing realistic delivery schedules.</p> Signup and view all the answers

In the context of aerial photography, what does stereo-plotting depend on?

<p>The number of models equals the number of photos minus one.</p> Signup and view all the answers

Identify two labor items typically considered when estimating costs for photogrammetric projects.

<p>Aerial photography and lidar data cleaning.</p> Signup and view all the answers

Why is flight planning necessary in drone operations?

<p>Flight planning ensures efficient and effective data collection while maximizing drone capabilities.</p> Signup and view all the answers

How does the urgency of a project to the client affect delivery schedules?

<p>Urgency can accelerate timelines and prioritize specific tasks within the project schedule.</p> Signup and view all the answers

What is the significance of ground control in determining processing parameters?

<p>Ground control is vital for accurate intrinsics and extrinsics determination in photogrammetry.</p> Signup and view all the answers

What is one reason flight planning is necessary for drone operations?

<p>To ensure that the drone flies safely, especially over larger areas where it can't be monitored directly.</p> Signup and view all the answers

How does the altitude of a drone affect the area it covers during flight?

<p>Higher altitudes allow the drone to cover a larger area.</p> Signup and view all the answers

What is Ground Sampling Distance (GSD) and why is it important in aerial imaging?

<p>GSD measures the accuracy of an image, indicating the real-world size each pixel represents. Smaller GSD values indicate a more detailed view.</p> Signup and view all the answers

What is Ground Sampling Distance (GSD) in the context of drone flight?

<p>GSD refers to how big each pixel is on the ground, indicating the level of detail in the images.</p> Signup and view all the answers

Why might a hobbyist prefer a quadcopter over fixed-wing drones for certain tasks?

<p>Quadcopters are easier to control and provide higher resolution images for small-area mapping.</p> Signup and view all the answers

Explain the significance of Ground Control Points (GCPs) in creating accurate 3D models.

<p>GCPs are reference points on the ground that help register aerial images to real-world coordinates. They ensure centimeter-level accuracy in mapping and modeling.</p> Signup and view all the answers

What are two applications for drones in serious fields beyond hobbies?

<p>Orthophoto Mosaic and Point Cloud/3D Models.</p> Signup and view all the answers

Describe the factors to consider when planning a flight for aerial photography.

<p>Factors include the areas to cover, desired accuracy (GSD), flight height and path, GCPs, overlap, sidelap, and type of drone used. Each factor influences the quality of the resulting images.</p> Signup and view all the answers

In what ways can improper flight planning affect drone image capture?

<p>It can lead to missing crucial images at the right time or capturing images at inappropriate altitudes.</p> Signup and view all the answers

Why might a drone require GCPs despite having onboard GPS?

<p>Onboard GPS may not provide the centimeter accuracy needed for precise mapping, making GCPs necessary for achieving high-accuracy results. GCPs improve the reliability of the aerial data.</p> Signup and view all the answers

What does it mean if a drone flight is described as having a higher resolution?

<p>It means the drone captures more detailed images, typically at lower altitudes.</p> Signup and view all the answers

How does image overlap contribute to creating seamless mosaics or 3D models?

<p>Image overlap ensures that adjacent images capture common areas, which aids in stitching them together seamlessly and provides depth for 3D modeling. It enhances the continuity and detail of the final product.</p> Signup and view all the answers

What critical aspect must be considered besides area of interest when designing a drone flight plan?

<p>Altitude is a critical aspect that affects image quality and coverage.</p> Signup and view all the answers

What is a common use of drones in filmmaking?

<p>Drones are used for aerial photography and video shooting.</p> Signup and view all the answers

Why might a fixed-wing drone be preferred for mapping larger areas?

<p>Fixed-wing drones are more stable during flight and can cover larger areas efficiently.</p> Signup and view all the answers

Study Notes

Digital Photogrammetry (GEOM 2020) - Week 5: Planning a Mapping Project - Flight & GCP

  • Course: Digital Photogrammetry (GEOM 2020)
  • Department: Geomatics Engineering and Land Management
  • Instructor: Dr. O.O. Aladejana
  • Week: 5
  • Topic: Planning a Mapping Project: Flight & GCP

Outline

  • Flight Planning: Crucial for effective aerial photography. Requires a meticulously planned photographic mission adhering to a flight plan (navigation map). The plan details where aerial photographs need to be taken. Important parameters are also included.
  • Planning the Ground Control: Establishing points with known positions on the ground to relate aerial photographs to the ground. Essential for all photogrammetric work.
  • Selecting Instruments: Choosing appropriate tools and equipment.
  • Estimating Costs and Delivery Schedules: Evaluating the cost of materials, labor, and overhead, crucial for project planning and realistic timelines.

Flight Planning

  • Purpose: Photography effectively fulfills its purpose when meticulously planned and executed according to a flight plan.
  • Flight Plan: A flight (navigation) map specifying where aerial photographs will be taken, along with important parameters.
  • Importance: Critical for success in any photogrammetric project.

Importance of Flight Planning

  • Critical Components:
    • Flight Plan: Locates areas to be photographed, detailing procedures.
    • Specifications: Outlines how photographs are taken (e.g., camera, scale, flying height, overlap, tilt).
  • Considerations:
    • Costly equipment and crew involved in aerial missions.
    • Limited timeframes due to weather and ground conditions.
    • Risk of Poor Planning: Project delays and costly re-flights.

Flight Planning Procedures

  • Factors for Determining a Flight Plan:
    • Photographic end lap and side lap
    • Purpose of photography
    • Photo scale
    • Flying height
    • Ground coverage
    • Weather conditions
    • Season of the year
    • Flight map

Photographic Overlap and Side Lap

  • Importance of Overlap: Ensures stereoscopic coverage throughout the project area. The photographs must overlap in two directions:
    • In the line of flight (Overlap): Needed for parallax.
    • Between adjacent flights (Sidelap): Avoids missing bits.
  • Standard Overlap:
    • Forward (in the line of flight) overlap: 60% - 70%
    • Lateral (between flight lines) overlap: 25% - 40%

Flight Line of Aerial Photography

  • Stereoscopic Model: Overlap in photographs enables creation of a stereoscopic model.
  • Ground Terrain Data: Successive photographs allow mapping of terrain.
  • Altitude (H): Represents altitude above ground level.

Purpose of Photography

  • Metric vs. Pictorial Qualities:
    • Metric: Required for topographic mapping or quantitative measurements (high precision).
    • Pictorial: Essential for qualitative analysis and visualization; used for interpretation, mosaics, and photomaps; useful with wider-angle cameras (short focal length).
  • Camera Types:
    • Calibrated cameras with known parameters, image resolution, and scaling factors necessary.
    • Fine-grained, high-resolution film or digital sensors with high pixel counts for accuracy.
  • Purpose Definition: Deciding on the end goal determines equipment and execution.

B/H' Ratio

  • Definition: Ratio of air base (B) of overlapping photos to average flying height (H').
  • Impact of High B/H': Larger intersection angles, better accuracy in determining ground points.
  • Impact of Low B/H': Smaller parallax angle, less accurate mapping.
  • Importance of B/H' Ratio: Crucial for accurate topographic mapping. Use of flying height and parallax angles necessary.

Photo Scale

  • Importance: Essential in planning aerial photography; generally fixed within specific project requirements.
  • Topography: The scale is typically dictated by the map's required scale and vertical/horizontal accuracy.
  • Photo Interpretation: The ability to see small ground features is the key factor in choosing the photo scale.
  • Minimum Scale: Calculates the minimum scale based on the desired resolution.

Flying Height

  • Determination: Once camera focal length and desired photo scale are set, the required flying height above average ground is automatically established.
  • Formula (Sp): Focal length of the camera (f) divided by the required average photo scale, then determined and adjusted for flight altitude relative to average elevation of terrain.
  • Example Calculations: Demonstrates calculating required flying height for a given project.

Ground Coverage

  • Calculation: The ground surface area covered by a single photograph (calculated once camera and scale are set).
  • Additional Factors: End lap and side lap allows for the area covered by a stereoscopic neat model.
  • Importance: Represents approximate mapping area of each stereopair.

Weather Conditions

  • Ideal Conditions: Clear skies with minimal (less than 10%) cloud cover. Overcast can be useful for particular areas, like urban areas, but clouds at or below flight level are problematic.
  • Unsuitable Conditions: Haze, smog, dust, smoke, and high winds can compromise photo clarity.
  • Precautions: Use yellow filters in haze and avoid flying during high winds or adverse weather conditions.

Season of the Year

  • Considerations: Deciduous trees need to be bare for a clear view of the earth, this avoids obscuring ground features.
  • Photographic Timeframe: Best times are in the spring and fall due to the condition of leaves on trees.
  • Shadow Considerations: Shadows can obscure details, but can sometimes be advantageous (e.g., identify tree species).
  • Sun Considerations: Low-angle sun causes long shadows, making photography difficult. The ideal time is when the sun is above 30 degrees to reduce shadows and improve images.

Flight Map

  • Definition: Presents project boundaries and the required flight lines needed for coverage.
  • Derivation: Based on topographic maps, small-scale aerial photos (which also represent the area), or ground features.
  • Piloting: Flight path along identifiable ground features ensures coverage. GPS can also be used.
  • Pilot Navigation: Uses features in the area to guide flight path and ensure coverage.

Flight Line Orientation

  • Rectangular Areas: North-south or east-west orientations are preferable.
  • Irregular Areas: Parallel lines to project boundaries are best.
  • Planning Templates: Transparent templates are used to display neat models in areas, helping to plan for the most economical coverage and to determine exposure locations.
  • Artificial Targets: Useful in applications needing precise measurements.

Planning the Ground Control

  • Essential Points: Relating photographs to the ground, essential in nearly all phases of photogrammetric work. Points must have known positions in a reference system.
  • Ground Control Points (GCPs): Points with known real-world coordinates used in photogrammetry to register to real-world references.

Ground Control Points (GCPs)

  • Definition: Points in a known position (object space).
  • Uses:
    • Geo-referencing products.
    • Accurate parameter determination (intrinsics & extrinsics).
    • Accuracy of finished photogrammetric products.
  • Types for Measurement: Horizontal, vertical, and full control points.

Cost Estimation and Delivery Schedules

  • Experience with similar projects: Crucial for realistic pricing on delivery.
  • Categories: Considerations for labor, materials, overhead, and profit.
  • Schedule: Depends on the number of instruments, people, amount of work in progress, and client urgency.

Drone Flight Planning: Principles and Practices

  • Drone Capabilities: Detailed information about drone abilities useful for various purposes.
  • Need for Planning: Why flight plans are necessary (e.g., safety, control).
  • Principles of Flight Plan Design: How to design effective flight plans.
  • Software for Drone Flight Planning: Examples of available software.

Drones (Quadcopters and Fixed-wing)

  • Quadcopter (Hobbyist/Small Area): Easier to control, and useful for high-resolution mapping.
  • Fixed-wing (Map Production/Large Area): Greater stability and capability of covering larger areas and useful for more production projects.

Drone Uses

  • Hobbies: Aerial photography, video, filmmaking.
  • Serious Applications: Orthophoto mosaics, point clouds, digital elevation models.

Why We Need Flight Planning

  • Ensuring Accuracy: Planning ensures capturing the images at the right time and position.
  • Drone Control: Allows for managing drones in large areas where visibility isn't apparent.
  • Safety: Enables drones to fly safely under safe conditions, especially in larger areas.

Drone Flight Plan Design

  • Area of Interest: Important for planning a flight path, covering all the areas necessary for the project.
  • Altitude: Key element in covering larger areas and also in terms of pixel details (ground sampling distance). High altitudes imply larger areas covered, but also less detail in the resulting images.
  • Overlap: Ensuring photos overlap (forward and side overlap). A precise number of overlaps allows for more precise stitching.

Ground Sampling Distance (GSD)

  • Definition: Measuring the size of a pixel on the ground. Smaller GSD means more detail but more photos.
  • Flight Height and Sensor: Larger flight height means a larger area coverage, but fewer pixels per area, reducing the details.

Overlap on Drone Imagery

  • Good Mosaic and 3D Models: Essential to create a good seamless mosaic/3D models, need to ensure images are overlapped.
  • Overlap Percentage: Critical for stitching photographs together and producing high-quality 3D models.
  • Insufficient Overlap: Resulting in gaps in images that result in a lack of seamless stitching.

Ground Control Points (GCPs)

  • Positioning: Used to register a set of images to standard real-world coordinates, essential for a complete mapping project.
  • GCP Use: Ensures the models are correctly registered to the real world, giving precision to the resulting outputs.

Software for Flight Planning

  • DroneDeploy: Automatic flight plan design.
  • Drone Harmony: Provides various tools.
  • PrecisionHawk: Offers features for various needs.
  • Lithi: Allows various tools for project visualization.
  • Height Tech: Enables various software implementations with more specialized functions.

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Drone Flight Planning: Principles and Practices PDF

Description

Test your knowledge on aerial photography concepts, including scales, flying heights, and ground coverage. This quiz covers essential principles such as the relationship between photographic scale, focal lengths, and adjustments needed for terrain elevation. Dive into the significance of flight planning and the importance of GPS in aerial surveys.

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