Geo referencing and Digitizing

 










Georeferencing

Step 1: Gather Data

  • Collect Base Map: Obtain a reference map (e.g., a scanned paper map or satellite image) that needs georeferencing.

Step 2: Open GIS Software

  • Load Data: Use GIS software (e.g., QGIS, ArcGIS) to open the base map.

Step 3: Define Coordinate System

  • Set CRS: Choose the correct coordinate reference system (CRS) for the project based on the data source.

Step 4: Add Control Points

  • Identify Reference Points: Select known geographic locations on the base map (e.g., intersections, landmarks).
  • Add Control Points: Mark these points and match them with their real-world coordinates.

Step 5: Perform Georeferencing

  • Transformation: Use the control points to align the base map to the correct spatial location.
  • Adjustments: Apply necessary transformations (e.g., affine, polynomial) for accuracy.

Step 6: Save Georeferenced Map

  • Export: Save the georeferenced map as a new file, ensuring it retains spatial reference.

Digitizing

Step 1: Prepare for Digitizing

  • Select Layer: Create or select an existing vector layer in GIS for digitizing.

Step 2: Start Editing

  • Activate Editing Mode: Enable editing for the selected layer in the GIS software.

Step 3: Digitize Features

  • Trace Features: Use the digitizing tool to trace over features on the georeferenced map (e.g., roads, boundaries).
  • Add Attributes: Input relevant attribute data for each feature being digitized.

Step 4: Save Edits

  • Save Changes: Regularly save digitized features to avoid data loss.

Step 5: Validate Data

  • Check Accuracy: Verify the digitized features align correctly with the georeferenced base map and correct any errors.

Step 6: Export Data

  • Finalize Layer: Save the digitized layer in the desired format (e.g., shapefile) for future use.

 

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