Great Lakes Bathymetry

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Partial Erie bathymetry cut with MPCNC, map from NOAA, processed with QGIS and Aspire 8.5

CNC Router Model

QGIS Workflow

  1. Download QGIS
  2. Download Great Lakes Bathymetry from NOAA's Grid Extract Tool by choosing "Great Lakes Bathymetry," selecting the then drawing a rectangle around the area
  3. Download greatlakes_subbasins.zip from Science Base
  4. Merge sections
    1. In QGIS, add subbasins.shp as Vector Layer
    2. Click Toggle Editing (pencil icon)
    3. Ctrl +A to select all elements
    4. Go to Edit -> Merge Selected Features
    5. Check that subbasins is now one polygon, Toggle Editing, save changes
  5. Add bathymetry rasters from NOAA's Grid Extract Tool, ensuring all area under buffers is included
  6. Merge images: Raster -> Miscellaneous -> Merge
  7. Choose raster files and name output file (e.g. greatLakes)
  8. Go to Raster -> Extraction -> Clipper
  9. Choose mask layer (greatLakes) and select subbasin mask
    1. If error Output driver `GMT' not recognised . . ., select pencil button next to output algorithm and change -of GMT to -of GTIFF
    2. If black 0-level box appears after masking, delete the files and re-run with large (-99999) number and No Data Value box selected

Proprietary Workflow (Aspire)

Video walkthrough here

  1. Data pulled from NOAA's ETOPO1 images, available directly here which offers a 1-minute resolution of worldwide bedrock
  2. Add raster image to QGIS
  3. Select extent desired (Raster -> Extraction -> Clipper)
  4. Export as .tiff
  5. Open in GIMP, click white area surrounding with Magic Wand Tool, then drag upward to increase threshold to maximum
  6. Overwrite .tiff to save
  7. Open in Aspire, under Modeling tab, select "Create a component from selected bitmap"
  8. Switch to 3D view so the changes are illustrated
  9. Right-click component under Component Tree, then select Properties
  10. Move Shape Height slider until desired relief is achieved (.95" was used for this project)
  11. Return to Drawing View. With image selected, choose Trace Bitmap (bird image under "Create Vectors")
  12. Increase threshold until outline only is left
  13. Switch to Toolpaths bar and select 3D Roughing Path
  14. Choose Selected Vector under Machining Limit Boundary, then press Calculate
  15. Press 3D Finishing Toolpath, then choose vector as above
  16. Preview the toolpaths to ensure desired results
  17. If image is larger than machine, use Tile Toolpaths to divide it [1]

Tool speeds used in above (wooden) image:

Print Pass Tool Size Feed Rate Plunge Rate Print Time
Rough Pass .25" square bit 15.0 mm/sec 3.0 mm/sec 1:30
Finish Pass .125" ball nose 25.0 mm/sec 6.0 mm/sec 4:30

STL for 3D Printing

  1. Open QGIS, add Vector, add layer file (.adf)
  2. Select extent (Raster -> Extraction -> Clipper)
  3. Save as GeoTIFF
  4. Add GeoTIFF to model
  5. Analyze to DEM (Raster -> Analysis -> DEM [Terrain Models])
  6. If necessary, merge the DEMs
  • A balance must be made between extent and resolution. 1:50,000 creates excellent models, but cannot contain an entire lake. Above that and the file crashes my system. A further note on resolution.
  • Solution to bathymetric (negative) altitude values[2]: using Raster Calculator, add bottom value to all height values
  1. Create STL (Raster -> DEMto3D)[3]

Laser Cut, Low Resolution

  1. Download shapefiles from NOAA. Superior bathymetry contours with unclear provenance is available here, with login
  2. Download and install QGIS and Inkscape[4]
  3. No need to extract files, open each in QGIS Desktop
  4. Add OpenStreetMap information if desired (the native support is not working at this time[5], but the plugin does)
  5. Right-click shapefile in left layers panel, select Properties
  6. Choose Filter, then create expression, e.g. "DEPTH" IN ('0', '1', '25', '50', '60')[6]
    • It is helpful to use the Values box (make sure "Use unfiltered layer" is checked if changing an applied filter) to see the extent of the map's values

Ideas

Resources

Other Sources

Maps of Geography

Maps of Ecosystem

References

  1. Vectric Ltd. "Vectric V8 Tutorials - Tiling 3D Toolpathing." YouTube. [1]
  2. Geographic Information Systems Stack Exchange. "Mars DTM has all negative elevations in QGIS. Can't build STL file for 3D print." here.
  3. Modified from Laguna Tools. "Max CNC Tutorial 3D Landscape." YouTube. here.
  4. Stack Exchange answer here
  5. "OpenStreetMap in QGIS." OpenStreetMap Wiki. here.
  6. Geographic Information Systems Stack Exchange. "QGIS choose contour line labels." Here
  7. Geographic Information Systems Stack Exchange. "Load .osm.pbf file in Qgis." here.