Surveying and mapping with photogrammetry in Drone Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is photogrammetry in the context of surveying and mapping?

Photogrammetry is the process of using photos, often taken by drones, to measure and create maps or 3D models of land and objects.

beginner

Why are drones useful for photogrammetry in surveying?

Drones can fly over areas quickly and capture many overlapping photos from different angles, which helps create accurate maps and 3D models.

intermediate

What is the importance of overlapping images in photogrammetry?

Overlapping images allow software to find common points between photos, which helps calculate distances and build accurate 3D models or maps.

intermediate

Name a common output product of photogrammetry used in surveying.

Common outputs include orthomosaic maps (flat, corrected images), digital elevation models (3D surface models), and point clouds (3D points representing surfaces).

advanced

What programming tasks might be involved in drone photogrammetry workflows?

Tasks include automating drone flight paths, controlling camera settings, processing images with photogrammetry software, and exporting map data.

What does photogrammetry primarily use to create maps?

A Satellite signals

B Photos taken from different angles

C Manual measurements with tape

D Radar waves

Photogrammetry uses photos taken from different angles to measure and map areas.

Why is image overlap important in photogrammetry?

A It helps software find matching points between images

B It reduces the number of photos needed

C It makes photos look brighter

D It saves drone battery life

Overlap allows software to match points in different photos to build accurate 3D models.

Which of these is NOT a typical output of photogrammetry?

A Text document

B Orthomosaic map

C Point cloud

D Digital elevation model

Photogrammetry outputs are visual or spatial data, not text documents.

What role does programming play in drone photogrammetry?

A Manually drawing maps

B Painting the drone

C Automating drone flights and image processing

D Flying the drone by hand

Programming helps automate drone control and image processing tasks.

Which device is most commonly used to capture images for photogrammetry in surveying?

A Laser scanner only

B Smartphone without camera

C Handheld GPS only

D Drone with camera

Drones equipped with cameras capture the images needed for photogrammetry.

Explain how drones and photogrammetry work together to create maps.

Think about flying, taking pictures, and building maps.

Describe the programming steps involved in automating a drone photogrammetry mission.

Consider what the drone and software need to do automatically.

Practice

1. What is the main purpose of using photogrammetry in drone surveying?

easy

A. To create maps and 3D models from overlapping photos

B. To control the drone's battery life

C. To improve the drone's flight speed

D. To reduce the number of photos taken

Solution

1. Step 1: Understand photogrammetry basics

   Photogrammetry uses many overlapping photos to build maps and 3D models.

2. Step 2: Identify the main goal in drone surveying

   The goal is to create accurate maps and 3D models from the photos taken by the drone.

3. Final Answer:

   To create maps and 3D models from overlapping photos -> Option A

4. Quick Check:

   Photogrammetry = maps and 3D models [OK]

Hint: Photogrammetry means building maps from photos [OK]

Common Mistakes:

• Confusing photogrammetry with drone battery management
• Thinking photogrammetry speeds up flight
• Assuming photogrammetry reduces photo count

2. Which of the following is the correct syntax to define a flight path list in Python for drone photogrammetry?

easy

A. flight_path = {"point1", "point2", "point3"}

B. flight_path = ("point1", "point2", "point3")

C. flight_path = ["point1", "point2", "point3"]

D. flight_path = "point1", "point2", "point3"

Solution

1. Step 1: Identify list syntax in Python

   Lists use square brackets [] with items separated by commas.

2. Step 2: Check each option

   flight_path = ["point1", "point2", "point3"] uses square brackets and quotes correctly for strings.

3. Final Answer:

   flight_path = ["point1", "point2", "point3"] -> Option C

4. Quick Check:

   List syntax = square brackets [OK]

Hint: Lists use square brackets [] in Python [OK]

Common Mistakes:

• Using parentheses instead of square brackets for lists
• Using curly braces which create sets, not lists
• Leaving out brackets and just separating by commas

3. What will be the output of this Python code snippet used in photogrammetry data processing?

photos = ["img1.jpg", "img2.jpg", "img3.jpg"]
processed = [photo.replace('.jpg', '.tif') for photo in photos]
print(processed)

medium

A. ["img1.tif", "img2.tif", "img3.tif"]

B. ["img1.jpg", "img2.jpg", "img3.jpg"]

C. ["img1.tif.jpg", "img2.tif.jpg", "img3.tif.jpg"]

D. SyntaxError

Solution

1. Step 1: Understand list comprehension with string replace

   Each photo filename has '.jpg' replaced by '.tif'.

2. Step 2: Apply replace to each item

   "img1.jpg" becomes "img1.tif", similarly for others.

3. Final Answer:

   ["img1.tif", "img2.tif", "img3.tif"] -> Option A

4. Quick Check:

   Replace '.jpg' with '.tif' = changed list [OK]

Hint: String replace in list comprehension changes extensions [OK]

Common Mistakes:

• Expecting original list without changes
• Thinking replace adds text instead of replacing
• Confusing syntax causing errors

4. Identify the error in this Python code snippet for planning drone photo overlap:

overlap = 0.7
if overlap > 1:
    print("Overlap too high")
else
    print("Overlap acceptable")

medium

A. Incorrect comparison operator in if statement

B. Missing colon after else statement

C. Variable overlap should be an integer

D. Print statements must be outside if-else

Solution

1. Step 1: Check syntax of if-else statements

   Python requires a colon ':' after else keyword.

2. Step 2: Identify missing colon

   Code has 'else' without a colon, causing syntax error.

3. Final Answer:

   Missing colon after else statement -> Option B

4. Quick Check:

   else: needs colon [OK]

Hint: Always put colon after else in Python [OK]

Common Mistakes:

• Forgetting colon after else
• Thinking overlap must be integer
• Misreading comparison operator

5. You want to generate a dictionary mapping photo filenames to their GPS coordinates after a drone flight. Which Python code correctly creates this dictionary from two lists: photos = ["img1.jpg", "img2.jpg", "img3.jpg"] and coords = [(34.5, -117.2), (34.6, -117.3), (34.7, -117.4)]?

hard

A. photo_coords = [photos, coords]

B. photo_coords = dict(zip(coords, photos))

C. photo_coords = {coords[i]: photos[i] for i in range(len(coords))}

D. photo_coords = {photos[i]: coords[i] for i in range(len(photos))}

Solution

1. Step 1: Understand dictionary creation from two lists

   We want keys as photo names and values as coordinates.

2. Step 2: Check each option

   photo_coords = {photos[i]: coords[i] for i in range(len(photos))} uses dictionary comprehension with matching indexes correctly.

3. Final Answer:

   photo_coords = {photos[i]: coords[i] for i in range(len(photos))} -> Option D

4. Quick Check:

   Dict keys=photos, values=coords [OK]

Hint: Use dict comprehension with index to pair lists [OK]

Common Mistakes:

• Swapping keys and values in dict
• Using zip with wrong order
• Creating list instead of dict